mu = On-Wafer Noise Measurements — As tran-
sistor technology evolves to smaller, lower-noise
devices used at higher frequencies, measuring their
noise characteristics becomes increasingly difficult.
The difficulties increase due to the very low noise
levels that must be measured and to the very high
reflections exhibited by such devices. We are de-
veloping accurate measurement techniques that can
be used to evaluate and improve physical models,
as well as design and predict the performance of
systems that employ transistors.

In order to characterize poorly matched transistors,
we extended and improved a Monte Carlo program
used for amplifier noise parameter uncertainty anal-
ysis and used it to perform simulations comparing
different measurement strategies. We developed the
capability to measure noise parameter of on-wafer
transistors or low-noise amplifiers. We performed
@ measurement comparison with two companies
of on-wafer noise parameters of CMOS transistors
with 0.13 micrometer gate lengths.

To better determine the optimal input source re-
flection coefficient, we developed an improved
on-wafer noise-parameter measurement method.

WorkKsHors

To disseminate newly developed on-wafer noise
measurements, we organized a joint International
Microwave Symposium (IMS)/IEEE Radio Fre-
quency Integrated Circuits (RFIC) full-day work-
shop on “Noise Measurement and Modeling for
CMOS” in San Francisco, CA, in June 2006.

New measurement techniques useful to wireless
engineers were presented in two full-day work-
shops at the IMS conference organized by project
members. One was on the topic “Memory Effects
in Power Amplifiers,” while the other was on
“Techniques and Applications of Wireless Sensor
Networks.”

REcENT PuBLicaTions

S. Lee, T. M. Wallis, J. Moreland, P. Kabos, and Y. C. Lee,
“Asymmetric Dielectric Trilayer Cantilever Probe for Calori-
metric High Frequency Field Imaging,” IEEE J. Microelectro-
mech, Syst. (in press).

E. Gerecht, D. Gu, F. Rodtiguez-Morales, and K. $, Yngvesson,
“Imaging and Spectroscopy at Terahertz Frequencies Using
Hot Electron Bolometer Technology,” Proc. SPIE Optics East,
Boston, MA, October 2006 (in press).

T. M. Wallis, J. Moreland, and P. Kabos, “Hinstein-de Haas
Effect in a NiFe Film Deposited on a Microcantilever,” Appl.
Phys. Lett. 89, 122502 (September 2006).

E, Gerecht, D. Gu, J. Randa, D. Walker, and R. Billinger,
“Terahertz Radiometer Design for Traceable Noise-Tempera-
ture Measurements,” Conf. Precision Electromagnetic Meas.
(CPEM) Digest, Torino, Italy, July 2006, pp. 660-661.

D. K. Walker and J. Randa, “On- Wafer Noise-Parameter Mea-
surements at NIST,” Conf. Precision Electromagnetic Meas.
(CPEM) Digest, Torino, Italy, July 2006, pp, 656-657.

F. Rodriguez-Morales, K, §. Yngvesson, R. Zannoni, E, Gerecht,
D. Gu, X. Zhao, N. Wadefalk, and J. Nicholson, “Development
of Integrated HEB/MMIC Receivers for Near-Range Terahertz
Imaging,” IEEE Trans. Microwave Theory Tech. 54, 2301-2311
(June 2006).

J. Randa, T. McKay, S. L. Sweeney, D. K. Walker, L. Wagner,
D. R. Greenberg, J. Tao, and G.A. Rezvani, “Reverse Noise
Measurement and Use in Device Characterization,” 2006 IEEE
Radio Frequency Integrated Cireuits (RFIC) Symp. Digest, San
Francisco, pp. 345-348 (June 2006).

S. Lee, ¥. C. Lee, T. M. Wallis, J. Moreland, and P. Kabos,
“Near-Field Imaging of High-Frequency Magnetic Fields with
Calorimetric Cantilever Probes,” J. Appl. Phys. 99, 08H306
(April 2006).

D. F. Williams, H. Khenissi, F. Ndagijimana, K. A. Remley,
J.P. Dunsmote, P, D. Hale, C. M. Wang, and T. S. Clement,
“Sampling-Oscilloscope Measurement of a Microwave Mixer
with Single-Digit Phase Accuracy,” /EEE Trans. Microwave
Theory Tech. 53, 1210-1217 (March 2006).

J, Randa, E. Gerecht, D, Gu, and R. L. Billinger, “Precision
Measurement Method for Cryogenic Amplifier Noise Tem-
peratures Below 5 K,” IEEE Trans. Microwave Theory Tech.
54, 1180-1189 (March 2006),

K.A. Remley, M. Rittschlin, D. F. Williams, R. T. Johnk, G.Ko-
epke, C. L, Holloway, M. Worrell, and A. MacFarlane, “Radio
Communications for Emergency Responders in Large Public
Buildings: Comparing Analog and Digital Modulation,” Proc.
2006 Intl. Symp. Advanced Radio Tech. (ISART), Boulder, CO,
pp. 79-82 (March 2006).

D.F, Williams, A. Lewandowski, T. S. Clement, C.M. Wang, P.
D. Hale, J.M. Morgan, D. Keenan, and A. Dienstftey, “Covari-
ance-Based Uncertainty Analysis of the NIST Electro-Optic
Sampling System,” JEEE Trans. Microwave Theory Tech. 54,
481-491 (January 2006).

J. R. Baker-Jarvis, “Time-Dependent Entropy Evolution in
Microscopic and Macroscopic Electromagnetic Relaxation,”
Phys. Rev. E72, 066613 (December 2005).

K. A. Remley, C. A. Grosvenor, R. T. Johnk, D. R. Novotny,
P. D. Hale, M. D. McKinley, A. Karygiannis, and E. Anton-
akakis, “Electromagnetic Signatures of WLAN Cards and
Network Security,” Proc, IEEE Int. Symp. Signal Processing
and Information Technology, Athens, Greece, December 2005,
pp. 484-488.

K. A. Remley, P. D. Hale, D. I. Bergman, and D. Keenan,
“Compatison of Multisine Measurements from Instrumentation
Capable of Nonlinear System Characterization,” 66th ARFTG
Microwave Measurements Conf. Digest, Washington, DC,
December 2005, pp. 34-43.



Test fixture head of a new apparatus to measure the
delamination strength of second-generation high-tem-
perature superconductors. The photo shows a YBCO
coated conductor tape mounted between the two anvils
of the apparatus.

Indeed, successful testing with the new apparatus
showed that slit conductors have a relatively low
transverse tensile strength. The overall strength of
the conductor is reduced significantly by the slitting
process. One company developed a structure to re-
inforce the slit conductor by soldering copper strips
around the conductor (three-ply structure). The
added solder joints at the edges of the conductor
help restore the overall strength. We are currently

3-ply
o Internal

sit

Transverse Tensile Strength [MPa]

collaborating with another company to find other
novel solutions to avoid edge damage caused by
slitting. In particular, we are pursuing solutions
that produce a strong conductor without the need
for extra reinforcement that lowers the conductor’s
overall critical current density.

m_ Discovery of Large Universal Effect of
Axial Strain on the Critical Current of High-
Temperature Superconductors — Although
remarkable technical advances have been achieved
during the past several years in the development of
high-temperature superconductors (HTS) for use
in large-scale applications, these have occurred
without a clear understanding of the underlying
mechanism of superconductivity in these materials.
One of the main areas not fully understood is the
change of the superconducting current density with
applied strain. We have discovered a very large uni-
versal, reversible change in the J,of YBCO coated
conductors, which is symmetric under both high
compressive and high tensile strain. We anticipate
these findings will initiate detailed research on the
effect of strain on the underlying mechanisms of
superconductivity in practical HTS. For instance,
strain fields at grain boundaries in HTS may be the
main limiting mechanism for supercurrents.

The superconducting current density in its self-field
decreases reversibly by more than 40 percent under
compressive strain in a wide range of conductors
fabricated by vastly different processes. The effect
is nearly the same for all high-current conductors
measured, including YBCO deposited by metal-
organic chemical vapor deposition (MOCVD)
(which results in a columnar YBCO grain struc-
ture), metal-organic deposition (MOD) (which
results in a laminar YBCO grain structure), and a
hybrid conductor fabricated with a double YBCO
layer (consisting of YBCO that is doped with a
large amount of Dy particles that provide extra flux
pinning centers). The effect is symmetric under
both compressive and tensile strains.

A major reversible strain effect is a consistent

o

Conductor slitting reduces the overall transverse ten-
sile strength to an average of 17.3 megapascals (num-
bers in the bars indicate the average value), which

is far below the average internal strength of 26.5
megapascals. Reinforcing the slit sample by soldering
copper strips (three-ply structure) raised the average
transverse tensile strength to 24.8 megapascals. The
solid parts of the bars give an indication of the spread
in strength among samples.

and intrinsic phenomenon of high-current YBCO
biaxially aligned coated conductors, encompass-
ing a number of different types fabricated with
widely varying YBCO deposition techniques. The
universality and symmetry provide evidence that
the mechanism behind the reversible strain effect
is an intrinsic feature of the YBCO grain structure
(columnar for MOCVD-IBAD and laminar for
MOD-RABIiTS). The results open the door for
detailed studies into the mechanism of supercon-
ductivity in HTS.



Goats

The Time-Domain Fields Project develops basic
metrology and measurement techniques for a wide
variety of applications such as antenna and sensor
calibrations, evaluation of electromagnetic compat-
| ibility (EMC) measurement facilities, shielding
performance of aircraft, nondestructive testing of
electrical material properties, precise generation
of standard fields, and detection of signals and
threats.

Customer NEEDS

Time-domain field methods use time windowing
to eliminate unwanted signals. These methods
find application to problems that cannot readily
be evaluated using traditional continuous-wave
radiated tests. In particular, time-domain methods
allow for localization of large systems and for
testing in highly cluttered environments. Customer
needs include:

Reflection Properties — EMC test sites, such as
anechoic chambers and open area test sites (OATS)
use absorbing and low-reflectivity materials to
achieve desired performance. The reflectivity of
these materials needs to be accurately characterized
over a wide frequency range, possibly in situ.

Shielding Effectiveness — Time-domain signals
can be used to investigate the shielding effective-
ness of large, complex geometries. Aircraft can be
tested in situ, either over tarmac or in a hanger.

Propagation in Buildings — Buildings present
| complicated propagation environments. Com-
\ munications system designers need to know how
| waves couple through differing building materials
| and how waves couple from the exterior to interior
. and between interior locations.

ELECTROMAGNETIC CompPaTIBILITY:
Time-Domain FiELps

bration up to 20 gigahertz, plus antenna calibration
and system characterization. We used extensive
numerical simulations to optimize the feed and
cone sections to achieve very high performance
levels.

We have been a leader in developing transverse
electromagnetic (TEM) horn antennas for receiv-
ing ultra-wideband signals. These antennas have
very linear phase characteristics and are able to
accurately preserve time-domain traces. We will
publish a NIST technical note that summarizes our
research in TEM Horns.

TEM horns are used in field-deployable systems
for transmitting and receiving time-domain fields.
The system uses optical fiber links to achieve
high isolation and dynamic range. The system has
been successfully applied to the evaluation of the
shielding effectiveness properties of commercial
and military aircraft. These efforts have assisted
NASA, U.S. manufacturers, the U.S. Department
of Defense (DOD), and the Federal Aviation Ad-
ministration (FAA), to improve flight safety and
reduce the vulnerability of aircraft to electromag-
netic interference and threats.

We are applying time-domain techniques to devel-
op a database of the electrical properties of building
materials in support of homeland security goals.
The database will help first responders develop
communication systems that will improve perfor-
mance in emergency situations. We are collaborat-
ing on the use of genetic algorithms to accurately
extract electrical parameters from time-domain
reflection and transmission data. We are also de-
ploying a portable measurement system to measure
the propagation characteristics of buildings over
ultra-wide bandwidths and provide both time- and
frequency-domain channel characteristics.

Technical Contact:
Robert Johnk

Staff-Years (FY 2006):
2.0 professionals
1.0 research associate

systems are being proposed to increase capacity

and to address advanced communications needs.
, Antenna characteristics and link performance need
| to be accurately determined.

‘
| Ultra-Wideband Systems — Ultra-wideband
\

| TECHNICAL STRATEGY

| We have developed measurement tools and systems
‘both to generate and receive ultra-wideband radi-
tated signals. We currently have a large cone and
ground plane facility. This facility can be used to
generate well defined pulse fields for sensor cali-

We have supported industry and standards groups
jn assessing the performance of electromagnetic fa-
cilities such as anechoic and semi-anechoic cham-
bers, shielded rooms, reverberation chambers, and
OATS facilities. The performance of microwave
absorbers has been measured. Many facilities use
Jow-reflectivity material for test object support and
weather protection. We are helping to develop time-
domain-based test methods to determine the effects
of “reflectionless” materials of the type specified
in many radiated test standards on site ability to
perform ultra-wideband RCS measurements.



January 2007

For additional information contact:

Telephone: (303) 497-3131

Facsimile: (303) 497-3122

On the Web: http:/Avww.boulder.nist.gov/div818/



current required for critical-current measurements
turns many minor measurement problems into
significant engineering challenges. For example,
heating of the specimen, from many sources, dur-
ing the measurement can cause a wire to appear to
be thermally unstable. Newer MgB, wires may be
used for specialty magnets that can safely operate
at the higher temperatures caused by high heat
loads. We need to make sure that our measure-
ments and the measurements of other laboratories
keep up with these challenges and provide accurate
results for conductor development, evaluation, and
application.

Possible spin-off applications of particle accelera-
tors are efficient, powerful light sources and free-
electron lasers for biomedicine and nanoscale ma-
terials production. The heart of these applications
is a linear accelerator that uses high-efficiency,
pure Nb resonant cavities. We conduct research
on a key materials property measurement for this
application, the residual resistivity ratio (RRR) of
the pure Nb. This measurement is difficult because
it is performed on samples that have dimensions
similar to those of the application. Precise variable-
temperature measurements are needed for accurate
extrapolations.

TECHNICAL STRATEGY
INTERNATIONAL STANDARDS

With each significant advance in superconductor
technology, new procedures, interlaboratory com-
parisons, and standards are needed. International
standards for superconductivity are created through
the International Electrotechnical Commission
(IEC), Technical Committee 90 (TC 90).

Critica. CURRENT MEASUREMENTS

One of the most important performance param-
eters for large-scale superconductor applications

Voltage (arbitrary units)

©

DC current (arbitrary units)

Illustration of a superconductor s voltage-current
characteristic with two common criteria applied.

is the critical current. Critical current is difficult
to measure correctly and accurately; thus these
measurements are often subject to scrutiny and
debate. The critical current is determined from a
measurements of voltage versus current. Typical
criteria are electric-field strength of 10 microvolts
per meter and resistivity of 10“ ohm-meters.

Critical-current measurements at variable tem-
peratures are needed to determine the temperature
margin for magnet applications. The temperature
margin is defined as the difference between the
operating temperature and the temperature at which
critical current J, is equal to the operating current.
When a magnet is operating, transient excursions
in magnetic field H or current J are not expected;
however, many events can cause transient excur-
sions to higher temperatures T, such as wire motion,
AC losses, and radiation. Hence the temperature
margin of a wire is a key specification in the design
of superconducting magnets. Variable-temperature
critical-current measurements require data acquisi-
tion with the sample in a flowing gas environment
rather than immersed in a liquid cryogen. Accurate
high-current (above 100 amperes) measurements
in a flowing gas environment are very difficult to
perform.

1000

1 1
90 100

Electric field versus current at temperatures from 7.0
to 8.3 kelvins in steps of 0.1 kelvins for a Nb,Sn wire.
These are typical curves for the determination of criti-
cal current,

Resipua. Resistivity Ratio
Measurements

The RRR is defined as the ratio of electrical resis-
tivity at two temperatures: 273 kelvins (0 degrees



Waverorm

We are developing calibration procedures for
today’s high-performance electrical probes for
on-wafer measurement. We are also laying the
foundations for 200 gigahertz to 400 gigahertz
calibrations for tomorrow’s on-wafer probes. We
are also developing techniques for performing non-
invasive high-impedance on-wafer waveform mea-
surements for characterization of signal integrity
in digital silicon integrated circuits (ICs) and other
small circuits. This effort is particularly important
for the development of electrical metrology for
nanoscale devices, which, due to their small sizes,
have extremely high electrical impedances.

Our plan is to electrically characterize an active
high-impedance probe with our existing VNA
calibration methods. We will then characterize
the same probe on our 200 gigahertz bandwidth
electro-optic sampling (EOS) system. This will
lay the groundwork for very high-speed, on-wafer
calibrations for digital IC and nanoelectronics. We
will develop joint time-domain/frequency-domain
uncertainty analysis for coaxial photodiode pulse
sources. The calibration and uncertainty represen-
tation will include imperfections in the electro-
optic sampling system and electrical mismatch
corrections, and will be suitable for calibrating
oscilloscopes with coaxial ports in either the time
or frequency domains to 110 gigahertz. We will de-
velop pulse sources with 400 gigahertz bandwidth
and, based on these sources, develop on-wafer
waveform characterization ability to 400 gigahertz.
We will apply high-speed waveform metrology
to microwave problems, including the character-
ization of electrical phase standards, microwave
sources, and microwave mixers.

AccomPLISHMENTS

ua Low Noise Amplifiers — Low-noise ampli-
fiers (LNAs) are used in a variety of applications
involving detection and processing of low-level
signals; noise parameters are the critical charac-
teristics of LNAs. We performed measurements
of the noise parameters of an LNA for an informal
comparison with another National Measurement
Institute (NMI) in order to verify international
agreement on such measurements.

a Microwave Brightness-Temperature Stan-
dards — New microwave remote-sensing ra-
diometers for weather, climate monitoring, and
other applications are designed for unprecedented
accuracy. In order to verify (and possibly to even
achieve) that accuracy, a stable, accurate reference

standard is required. We proposed and documented
a plan for development of national microwave
brightness-temperature standards, traceable to
fundamental noise standards.

= Calibration Targets — Heated calibration
targets are commonly used as standards for micro-
wave remote sensing radiometers, but important
characteristics of such targets are not well mea-
sured. We performed preliminary measurements
of the electromagnetic properties of materials
commonly used in calibration targets with the
Electromagnetic Properties of Materials Project
and also performed infrared imaging of thermal
gradients in a target borrowed from NASA with
the Physics Laboratory. With the Radio-Frequency
Fields Group, we performed a preliminary study of
near-field effects on the calibration of microwave
radiometers when the calibration target is in the
near field of the radiometer antenna. It is current
practice to ignore such effects; however, this study
indicated that they could be significant.

= International Comparisons — Under the
Mutual Recognition Agreement (MRA) of NMIs
worldwide, measurement comparisons among
NMIs are performed on key quantities to assure
international harmonization of standards and of
measurements for commercial regulatory pur
poses, We participated in two completed Consul-
tative Committee for Electricity and Magnetism
(CCEM) Key Comparisons (KCs) in noise, one
KC in s-parameters, one KC in power, and one
supplementary comparison in power, for which
we were the pilot lab.

m= WR-15 and WR-10 Waveguide Systems
— Waveguide services above 50 gigahertz are
being revitalized to compensate for difficulties
with existing transfer standards and to improve
the traceability for high frequency signals used in
digital communications. A direct-comparison sys-
tem for WR-15 waveguide has been implemented
and is being used for customer calibrations. A
WR-10 waveguide system has been constructed.
These systems greatly reduce the time required for
a measurement. New WR-15 and WR-10 calorim-
eters were designed and tested. After initial tests, it
was decided to modify the new design to improve
their performance.

= Microwave Field Strength — Basic research
testing a fundamentally new method for measuring
microwave signal strength was conducted in col-
laboration with the Physics Laboratory. The RF
magnetic field strength in a cavity was measured by
observing the oscillation of cesium atoms between



Appenpix B:
PostpocToRAL RESEARCH ASSOCIATESHIPS

NIST offers postdoctoral research associateships in collaboration with the National Research Council
(NRC). Research topics and associated advisors for the Electromagnetics Division are listed below.
Complete information and applications forms for all NIST NRC postdoctoral offerings are available on
the Web at http://www7.nationalacademies.org/rap/. Contact a prospective advisor to discuss details of
proposed work and the application process. If you do not find a topic that exactly matches your inter-
est, please contact an advisor in a similar discipline. U.S. citizenship is required for NRC postdoctoral
appointments.

NISTs Boulder, Colorado, laboratories are located adjacent to the eastern foothills of the Rocky Mountains.

ELecTROMAGNETIC Properties OF MATERIALS
J. R. Baker-Jarvis

Research opportunities exist for theoretical and experimental investigations related to the precise charac-
terization of the macroscopic and microscopic electromagnetic properties of artificial, substrate, liquid,
and thin-film materials in the radio-frequency to terahertz frequencies. Suggested research areas include
the measurement of ultra low-loss dielectric and magnetic materials, thin films, nanowires, ferroelectric
materials, metamaterials, and nanoscale materials. Current interests also include the relationship of
quantum-coherence to dielectric loss, the relationships of complex permittivity to material mechanical
stress, linear and nonlinear response theory, dielectric measurements of liquids, ferroic materials, and
biased ferrite and ferroelectric measurements. In addition to excellent computational resources, a wide
range of experimental resonators, well characterized materials, laboratory instrumentation, environmental
facilities (e.g., a cryostat, a high-temperature chamber, and a magnetic bias capability), and a diversity
of related intellectual resources are available to facilitate research.

Broapsanb IMPEDANCE MEASUREMENTS OF THIN-FiLw ELECTRONIC
Materiacs anp Devices

J.C. Booth

Electrical impedance measurements provide important information about the response of materials to
electromagnetic stimuli. Therefore, impedance is a key parameter for the evaluation of new thin-film
materials that are being developed for next-generation electronic applications. A detailed understanding
of the evolution of the electrical impedance of thin-film materials and devices with increasing frequency
is required for determining the suitability of new materials for high-speed applications, and can also
provide valuable insight into the underlying physical processes relevant for advanced electronic materi-
als. We are developing new broadband impedance measurements of thin-film materials and devices in

BEléctronicsra

Sctricallenginecningieabona



j

tion with respect to its orbit about the Earth. This
feature is exploited in many modern technologies
such as wireless communications, the American
power grid, various power combining architectures,
and phased array antenna networks. One of the
simplest methods of synchronizing electronic based
oscillators is through the application of an AC
signal close to the oscillator’s natural frequency,
inducing the device to oscillate sympathetically at
the drive frequency.

We have directly measured phase locking of spin
transfer oscillators to an injected AC current. In this
scenario, the devices are forced to oscillate at the
same frequency as the injected signal. The oscilla-
tors lock to signals up to several hundred megahertz
away from their natural oscillation frequencies,
depending on the relative strength of the input. As
the DC current passing through the devices varies
over the locking range, time-domain measurements
show that the phase of the spin-transfer oscilla-
tions varies over a range of approximately plus or
minus 90 degrees relative to the input. This is in
good agreement with general theoretical analysis
of injection locking of nonlinear oscillators.

01 02 03 04 05 06 07
Time (ns)

Time-domain data showing the relative variation of
the oscillator phase over the locking range for several
values of DC bias current.

= Mutual Synchronization of Spin-Transfer
Oscillators — Our demonstration that spin-transfer
oscillators interact with input signals nonlinearly
opens the possibility of creating phase-coherent
device arrays. The power emitted from a single
spin-torque nano-oscillator (STNO) is at present
typically less than 1 nanowatt. To achieve a more
useful power level, on the order of microwatts, a
device could consist of an array of phase coherent
STNOs, as has been done with arrays of Josephson
junctions and larger semiconductor oscillators. We
showed that two STNOs in close proximity mutu-

Elect

lec

miners eat

ally phase-lock (that is, synchronize), exhibiting a
general tendency of interacting nonlinear oscillator
systems.

The phase-locked state is distinct, characterized
by a sudden narrowing of signal linewidth and
an increase in power due to the coherence of the
individual oscillators. For instance, the device
oscillator linewidth decreases by a factor of 10 as
compared to the individual oscillators, a significant
improvement with respect to thermal fluctuations.
Furthermore, we showed that the combined power
output represents a fully coherent combination of
the two signals, a requirement to demonstrate true
phase-locking between the devices,

Micromagnetic simulations showing the spin-wave
interaction between two local spin transfer oscillators.
Each device emits spin-waves towards the other, caus-
ing the devices to synchronize.

m Determination of Synchronization Mecha-
nism in Spin-Transfer Nanocontacts — The
fact that two spin-transfer nanocontact oscillators
fabricated in close proximity to each other on the
same magnetic film can phase-lock provides a
means for coherently combining the powers of the
devices. Furthermore, the power level increases
as the square of the number of oscillators. While
a promising result, an important question facing
further development is the origin of the phase-
locking. Spin-transfer nano-oscillators have at
least two possible means of interacting. Since the
devices produce magnetic fields, the oscillators
could simply interact like two bar magnets, with
the field from one affecting the oscillations of the
other. Alternatively, since the oscillators are con-
nected via a magnetic film, they could interact via
propagating “spin-waves.” Spin-waves are analo-
gous to water waves that propagate from the splash
produced by a rock thrown into a pool.

To separate these two possible mechanisms, we
devised a set of experiments. First, we fabricated
two oscillators on a magnetic film and showed that

metnecting) Leoraiony |



REcENT PuBLICATIONS

M.A. Hoefer and T. J. Silva, “Spin Momentum Transfer and
Oersted Field Induce a Vortex Nano-Oscillator in Thin Ferro-
magnetic Film Devices” (submitted for publication).

A.B. Kos and D. C. Hurley, “Nanomechanical Mapping with
Resonance Tracking Scanned Probe Microscope” (submitted
for publication).

J. R. Guerrieri, M. H, Francis, P. F. Wilson, A. B. Kos, L.
E. Miller, N. P, Bryner, D. W. Stroup, and L. Klein-Berndt,
“RFID-Assisted Indoor Localization and Communication for
First Responders,” Proc. Antenna Measurement Techniques
Association (AMTA), Austin, TX (October 2006); Proc. Euro-
pean Conference on Antennas and Propagation, Nice, France
(November 2006).

S. 8. Kalarickal, P. Krivosik, M. Z. Wu, C. E. Patton, M.
L. Schneider, P. Kabos, T. J. Silva, and J. P. Nibarger, “Fer-
romegnetic Resonance Linewidth in Metallic Thin Films:
Comparison of Measurement Methods,” J. Appl. Phys. 99,
093909 (May 2006)..

T. Gerrits, M. L. Schneider, A. B. Kos, and T. J. Silva, “Large-
Angle Magnetization Dynamics Measured by Time-Resolved
Ferromagnetic Resonance,” Phys, Rev. B 73, 094454 (March
2006).

T. Gertits, T. J. Silva, and T. Rasing, “Component-Resolved
Determination of the Magnetization by Magnetization-Induced
Optical Second-Harmonic Generation,” Rev. Sci. Instrum. 77,
034704 (March 2006).

T. Gerrits, M. L. Schneider, and T. J. Silva, “Enhanced Ferro-
magnetic Damping in Permalloy/Cu Bilayers,” J. Appl. Phys.
99, 023901 (January 2006).

M.R. Fitzsimmons, T. J. Silva, and T. M. Crawford, “Surface
Oxidation of Permalloy Thin Films,” Phys. Rev. B 73, 014420
(January 2006).

M.A. Hoefer, M. J. Ablowitz, B. Ilan, M. R. Pufall, and T. J.
Silva, “Theory of Magnetodynamics Induced by Spin Torque
in Perpendicularly Magnetized Thin Films,” Phys. Rey. Lett.
95, 267206 (December 2005).

R. Bonin, M. L. Schneider, T. J. Silva, and J. P. Nibarger, “De-
pendence of Magnetization Dynamics on Magnetostriction in
NiFe Alloys,” J. Appl. Phys. 98, 123904 (December 2005).

D. C. Hurley, M. Kopycinska-Milller, A. B. Kos, and R. H.
Geiss, “Nanoscale Elastic-Property Measurements and Mapping
Using Atomic Force Acoustic Microscopy Methods,” Meas. Sci.
Technol. 16, 2167-2172 (November 2005).

S. Kaka, M. R. Pufall, W. H. Rippard, T. J. Silva, S. E. Russek,
and J. A. Katine, Mutual Phase-Locking of Microwave Spin
Torque Nano-Oscillators, Nature 437, 389-392 (September
2005).

M.L. Schneider, T. Gerrits, A. B. Kos, and T. J. Silva, “Gyro-
magnetic Damping and the Role of Spin-Wave Generation in
Pulsed Inductive Microwave Magnetometry,” Appl. Phys. Lett.
87, 072509 (August 2005).

W.H. Rippard, M. R. Pufall, S. Kaka, T. J. Silva, S. B. Russek,
and J. A. Katine, “Injection Locking and Phase Control of
Spin Transfer Nano-Oscillators,” Phys. Rev. Lett. 95, 067203
(August 2005).

D. C. Hurley, A. B. Kos, and P. Rice, “Nanoscale Elastic-
Property Mapping with Contact-Resonance-Frequency AFM,”
in Scanning-Probe and Other Novel Microscopies of Local
Phenomena in Nanostructured Materials, eds. 8. V. Kalinin, B.
Goldberg, L. M. Eng, and B. D. Huey, Proc. Mater. Res. Soc.
Symp., Fall 2004, vol. 838E, paper 08.2 (June 2005).

M. L, Schneider, A. B. Kos, and T J. Silva, “Dynamic An-
isotropy of Thin Permalloy Films Measured by Use of Angle-
Resolved Pulsed Inductive Microwave Magnetometry,” Appl.
Phys, Lett, 86, 202503 (May 2005).

F. T. Chanock, R. Lopusnik, and T. J. Silva, “Pump-Probe
Faraday Rotation Magnetometer Using Two Diode Lasers,”
Rev. Sci. Instrum. 76, 056105 (May 2005).

S. E, Russek, S. Kaka, W. H. Rippard, M. R. Pufall, and T. J.
Silva, “Finite-Temperature Modeling of Nanoscale Spin-Trans-
fer Oscillators,” Phys. Rev. B71, 104425 (March 2005).

M. R. Pufall, W. H. Rippard, S. Kaka, T. J. Silva, and S. E.
Russek, “Frequency Modulation of Spin-Transfer Oscillators,”
Appl. Phys. Lett. 86, 082506 (February 2005).

S. Kaka, M. R. Pufall, W. H. Rippard, T. J. Silva, S. E. Russek,
J.A. Katine, and M. Carey, “Spin Transfer Switching of Spin
Valve Nanopillars Using Nanosecond Pulsed Currents,” J.
Magn. Magn. Mater. 286, 315-380 (February 2005).

J. P. Nibarger, R. L. Ewasko, M. L. Schneider, and T. J. Silva,
“Dynamic and Static Magnetic Anisotropy in Thin-Film Cobalt
Zirconium Tantalum,” J. Magn. Magn. Mater. 286, 356-361
(February 2005).

T. Gerrits, T. J Silva, J. P. Nibarger, and T. Rasing, “Large-Angle
Magnetization Dynamics Investigated by Vector-Resolved
Magnetization-Induced Optical Second-Harmonic Generation,”
J. Appl. Phys. 96, 6023-6028 (December 2004).

F.da Silva, W. C. Uhlig, A. B. Kos, S. Schima, J. Aumentado, J.
Unguris, and D. P. Pappas, “Zigzag-Shaped Magnetic Sensors,”
Appl. Phys. Lett. 85, 6022-6024 (December 2004).

W. H. Rippard, M. R. Pufall, S. Kaka, T. J. Silva, and S. E.
Russek, “Current-Driven Microwave Dynamics in Magnetic
Point Contacts as a Function of Applied Field Angle,” Phys.
Rev. B70, 100406 (September 2004).

M. L. Schneider, A. B. Kos, and T. J. Silva, “Finite Coplanar
‘Waveguide Width Effects in Pulsed Inductive Microwave Mag-
netometty,” Appl. Phys. Lett. 85, 254-256 (July 2004).

H. Okumura, C. ¥. Um, 8. Y. Chu, M. E. McHenry, D. E.
Laughlin, and A. B. Kos, “Structure and Magnetic Switching of
Thin Film HITPERM/SiO, Soft Magnetic Multilayers,” IEEE
‘Trans. Magn. 40, 2700-2702 (July 2004).

M. R.Pufall, W. H. Rippard, S. Kaka, S. E. Russek, T. J. Silva,
J. Katine, and M, Carey, “Large-Angle, Gigahertz-Rate Random
Telegraph Switching Induced by Spin-Momentum Transfer,”
Phys. Rev. B 69, 214409 (June 2004),

W. H. Rippard, M. R. Pufall, S. Kaka, S. E. Russek, and T. J.
Silva, “Direct-Current Induced Dynamics in Co,,Fe,/Ni,.Fe,,
Point Contacts,” Phys. Rev. Lett. 92, 027201 (January 2004).

ony,



or storing data in MRAM devices. We measure the
sensors using microwave excitation fields and field
pulses with durations down to 100 picoseconds. We
compare measured data to numerical simulations
of the device dynamics to determine the ability of
current theory and modeling to predict the behavior
of magnetic devices. We develop new techniques
to control and optimize the dynamic response of
magnetic devices. These include the engineering of
magnetic damping by use of rare-earth doping and
precessional switching, which controls switching
by use of the timing of the pulses rather than pulse
amplitude. This research is aimed at developing
high-frequency magnetic devices for improved
recording heads and for imaging of microwave
currents in integrated circuits and microwave
devices, Novel device structures that incorporate
magnetic materials with other nanostructures,
such as carbon nanotubes, are being investigated
in collaboration with the Materials Science and
Engineering Laboratory and the Radio-Frequency
Electronics Group.

Carbon nanotubes growing from Fe nanodots for use
in studying spin transport in nanostructures,

Maenetic Noise ano Low-Fietp
Maenetic Sensors

In collaboration with the Quantum Electrical
Metrology Division, we develop new techniques
to measure both the low-frequency and high-fre-
quency noise and the effects of thermal fluctuations
in small magnetic structures. Understanding the
detailed effects of thermal magnetization fiuctua-
tions will be critical in determining the fundamental
limit to the size of magnetic sensors, magnetic
data bits, and MRAM elements. High-frequency
noise is measured in our fabricated structures and

in commercial read heads. High-frequency noise
spectroscopy directly measures the dynamical
mode structure in small magnetic devices. The
technique can be extended to measure the dynami-
cal modes in structures with dimensions as small
as 20 nanometers. The stochastic motion of the
magnetization during a thermally activated switch-
ing process is measured directly, which will lead
to a better understanding of the long-time stability
of high-density magnetic memory elements. New
methods are being developed to dynamically im-
age thermal fluctuations by use of time-resolved
Lorentz and scanned probe microscopies. These
new metrologies will be essential to study and con-
trol thermal fluctuations and 1/fnoise in magnetic
and spintronic devices.

NaNomacnetism

We are developing new methods to characterize
the magnetic properties of nanomagnetic structures
such as patterned media and molecular nanomag-
nets. Patterned magnetic nanodots are fabricated
with sputter deposited magnetic multilayers and
electron-beam lithography. The magnetic proper-
ties are studied with magnetic force microscopy,
magneto-optical Kerr effect, and Lorentz mi-
croscopy. An important focus of this work is the
ability to characterize dynamics, such as magnetic
recording bit reversal, in single nanostructures at
high frequencies. Magnetic nanostructures are also
characterized with high-frequency EPR, based on
a superconducting quantum interference device
(SQUID) magnetometer, which can simultane-
ously measure low-frequency magnetic proper-
ties and high-frequency characteristics, such as
resonant absorption/emission of microwaves in
the frequency range of 95 to 141 gigahertz over a
temperature range of 1.8 to 400 kelvins. Molecular
nanomagnets, which are the smallest well defined
magnetic structures that have been fabricated,
exhibit quantum and thermal fluctuation effects
that will necessarily be encountered as magnetic
structures shrink into the nanometer regime. These
systems, which contain from 3 to 12 transition-
metal atoms, form small magnets with Curie tem-
peratures of 1 to 30 kelvins. We are investigating
new methods of manipulating these nanomagnets
by varying the ligand structure and binding them to
various films. We are looking at new applications
by incorporating the nanomagnets into molecular
devices and exploring how the nanomagnets relax
nuclear spins in biological systems.

ingjLaboratonyy



D. Das, A. Saha, C. M. Srivastava, R. Raj, 8. E. Russek, and
D. Bahadur, “Magnetic and Electrical Transport Properties of
La, ,,Ca,,,Mn0, (LCMO): xSiCN Composites,” J Appl. Phys.
95, 7106-7108 (June 2004).

A.T. McCallum and S, E. Russek, “Current Density Distribution
ima Spin Valve Determined Through Jn Situ Conductance Mea-
surements,” Appl. Phys. Lett. 84, 3340-3342 (April 2004).

E. Mirowski, J. Moreland, 8. E, Russek, and M. J. Donahue,
“Integrated Microfluidic Isolation Platform for Magnetic Par-
ticle Manipulation in Biological Systems,” Appl. Phys. Lett. 84,
1786-1788 (March 2004).

W.H. Rippard, M. R. Pufall, S. Kaka, 8. E. Russek, and T. J.
Silva, “Direct-Current Induced Dynamics in Co,,Fe,,/Ni
Point Contacts,” Phys. Rev. Lett, 92, 027201 (January 2004).



m= The second-harmonic magneto-optic Kerr ef-
fect (SH-MOKE) is especially sensitive to surface
and interface magnetization. We have used SH-
MOKE for time-resolved vectorial measurements
of magnetization dynamics and to demonstrate the
coherent control of magnetization precession.

m= In our pulsed inductive microwave magne-
tometer (PIMM), the changing magnetic state ofa
specimen is deduced from the change in inductance
ofa waveguide. This technique is fast, inexpensive,
and easily transferable to industry. It may also be
used as a time-domain permeameter to character-
ize magnetic materials. Since the development
of the PIMM at NIST, similar systems have been
built at several industrial research laboratories and
universities.

While these instruments have immediate use for the
characterization of magnetic data-storage materials,
they are also powerful tools for the elucidation of
magnetodynamic theory. The primary mathemati-
cal tools for the analysis of magnetic switching data
are essentially phenomenological. As such, they
have limited utility in aiding industry in its goal of
controlling the high-speed switching properties of
heads and media, We seek to provide firm theoreti-
cal foundations for the analysis of time-resolved
data, with special emphasis on those theories that
provide clear and unambiguous predictions that
can be tested with our instruments.

Time-resolved magneto-optic microprobe and pulsed
inductive microwave magnetometer (PIMM) con-
figured to simultaneously measure magnetization
dynamics. Comparison of the two techniques permits
quantitative determination of linewidth contribution
due to spatial inhomogeneity of the gyromagnetic

frequency.

TuEorY FoR Spin Torque NaNo-
OsciLLators

Our goal is to develop analytical and computational
methods for the modeling and design of nanome-
ter-scale ferromagnetic multilayer systems where
the spin-momentum-transfer effect is applied. The
recent discovery and rapid development of these
types of systems represent major technological
advances, with great promise for technological
applications. Spin momentum transfer (SMT)
generates microwave oscillations with narrow
linewidths in thin magnetic multilayers. As such,
these systems have the potential for next-generation
signal processing and communications applica-
tions. Experimental work in this field has proceeded
at an incredible rate, but theoretical understanding
lags behind. Fundamental questions involving
nonlinear effects on oscillator properties such as
line width, power, and the frequency dependence
on system parameters remain open. Our current
research, in collaboration with the University of
Colorado-Boulder, has demonstrated that care-
ful mathematical modeling is very effective in
describing the behavior of real systems. We have
undertaken a broad investigation of SMT systems
in order to fundamentally understand the SMT
effect so that it may be exploited in important ap-
plications including wireless communications and
fast, high-density data storage.

ACCOMPLISHMENTS

m Analytical Model for Spin-Torque Nano-
Oscillators — We developed a nonlinear model of
spin-wave excitation using a point contact ina thin
ferromagnetic film. Large-amplitude magnetic soli-
tary waves were computed using the model, which
helps explain the dependence of frequency on cur-
rent in recent spin-torque experiments. Numerical
simulations of the fully nonlinear model predict
excitation frequencies in excess of 0.2 terahertz
for contact diameters smaller than 6 nanometers.
These simulations also predict a saturation and
red-shift of the frequency at currents large enough
to invert the magnetization under the point contact.
The nonlinear frequency shift caused by increasing
current was found by means of numerical perturba-
tion techniques, which agree with direct numerical
simulations. The model was extended to include the
Oersted magnetic field generated around the point
contact due to the current flow. The presence of the
Oersted field fundamentally changes the symmetry
of the excited mode from even to odd symmetry for
inversion about the center of the point contact.



Evanescent microwave probe for on-chip dielectric
measurements.

AccompPLisHMENTS

= Complex Permittivities — In response to
homeland security needs and as a result of an in-
dustrial collaboration, we developed improved me-
trology and software for measuring the broadband
complex permittivity of foams and liquids. The new
software is based on an in-house theoretical model
for the open-circuited sample holder. We mea-
sured the permittivity of lossy foams over K-band
frequencies. We completed a Standard Reference
Material (SRM) for both relative permittivity and
loss tangent.

In a basic research study we applied broadband
permittivity measurement techniques to a range of
thin-film material systems, including ferroelectrics
as well as voltage-tunable dielectrics and artificial
multiferroics. These measurements included broad-
band voltage-dependent measurements of SrTiO,
thin films at cryogenic temperatures, as well as
measurements of Ba,Sr,,TiO; thin films at room
temperature. We have applied our broadband mea-
surement technique to artificial multiferroic thin-
film samples, which are multilayers of ferroelectric
PbTiO, and ferromagnetic Co-Fe-O, We performed
measurements of these multiferroic samples under
combined electric- and magnetic-field biases.

Jn order to study new approaches for permittiv-
ity determination we developed our broadband
nonlinear measurement system for characterizing
the broadband nonlinear microwave response. We
have also developed the detailed nonlinear models
used to analyze the measurement results obtained
with this measurement system. Application of
our measurement and analysis techniques to high
temperature superconducting transmission lines
has demonstrated experimentally the equivalence
of different manifestations of nonlinear response

(third harmonic generation, intermodulation
distortion) in the same device, and has provided
evidence of an inductive origin for the nonlinear
response in these materials. Measurements of the
nonlinear response of other ferroelectric materials
at room temperature have displayed a range of
behaviors, including a much larger intermodula-
tion signal in ferroelectric BaSrTiO;, a smaller
microwave nonlinear capacitance compared to
the DC nonlinear capacitance, and the dominance
of the nonlinear conductance term in ferroelectric
PbTiO; samples.

m Properties of Advanced/Emerging Materi-
als — In response to internal NIST nanowire efforts
we developed a new method for measuring the
electrical conductivity of bulk samples of carbon
nanotubes using a dielectric resonator and in-house
developed software. We performed measurements
and published a paper on the resonance phase in
metamaterials.

= Evanescent Probe Metrology and Theory —
The microelectronics industry roadmap highlights
the importance of on-chip probing. In response to
this need we have completed a theory for character-
izing the microscopic fields present while perform-
ing on-chip permittivity measurements. In order to
better understand our permittivity measurements,
we developed from basic statistical mechanics the
microscopic and macroscopic relationships for the
entropy in electromagnetic driving; this work has
been published in Physical Review E. We also de-
veloped a polarization evolution model that relates
relaxation times to the permittivity.

m= Semiconductor Materials — Through
conversations with industry representatives and
NIST personnel, we have determined that refined
characterization of semiconductors is needed. We
obtained a suite of commonly used semiconductors
used by researchers in the semiconductor industry
and the Optoelectronics Division and performed
variable frequency and variable temperature
measurements on the materials. In addition, we
characterized the permittivity of substrates as a
function of frequency and temperature for the
LTCC industry.

m= High-Frequency Measurement System
— In order to meet the needs for measurements at
higher frequencies we designed and constructed a
new Fabry-Perot mirror, and preliminary measure-
ments on two reference materials were performed.
To expand on these results, a confocal Fabry-Perot
system has been ordered and will also operate up
to 100 gigahertz.



@ MOCVDIBAD+CU 49 a
© MOGVDABAD

42°09 06 03 09 03 06
4 [%)

¥ MOD-RABITS +Cu 10

© MOD-RABITS b

A. Hybrid-MOD-RABITS +Cu

Ise )HA9)

a= 8402

Normalized superconducting current density plotted as
Function of intrinsic strain e, for three different types of
samples: MOCVD-IBAD, MOD-RABITS, and (hybrid)
MOD-RABITS, for both bare samples and those with
copper added for stability. The solid lines describe a
power-law function. The values of the strain-sensitivity
parameter a are included in the figure. Compressive
strain is indicated by negative values of &; tensile
strain is positive.

a Sample

Illustration of method for applying large axial strains
to superconducting sample that is soldered on top of
a Cu-2%Be bending beam. Axial tension is applied
by bending the beam in the direction shown in (a),
whereas axial compression is applied by bending the
beam in the opposite direction (b). Strain is uniform
over the thickness of the superconducting films to
within about 1 part in 2500.

mu Slit YBCO Coated Conductors Prove
Mechanically Robust Under Fatigue Cycling
— In order to evaluate the effect of slitting, we
used fatigue cycling under transverse compressive
stress, since earlier experiments had shown this to

induce crack propagation. Stress was applied to
the tape sample by means of two stainless-steel
anvils. Uniformity of stress over the pressed area
of the conductor was achieved by beveling the
edges of the top anvil, and attaching it to a biaxially
gimbaled pressure foot so that this anvil conforms
precisely to the bottom anvil and sample surfaces.
Stress was cycled between positive and negative
150 megapascals (about twice the stress level of
most applications) at a frequency of 1 hertz for
up to 20,000 fatigue cycles. J, was measured at
76 kelvins in self-field. These tests simulate condi-
tions in applications such as electric generators and
industrial magnets, and evaluate whether fatigue
exacerbates cracks by propagating them into the
middle of the conductor. The measurements also
help discriminate between different slitting tech-
niques. The samples investigated exhibited no
significant degradation under fatigue testing, thus
demonstrating that, unlike transverse-tension test-
ing, slitting does not affect the sample performance
under transverse-compressive-stress cycling.

Fatigue test fixture showing the top anvil, biaxially
gimbaled to uniformly apply pressure to the conductor.

N
o

G

Q

“e

S

z

2

> DT ttt eet tet oetgccetetege ett |
a

2

S

: 150 MPa

= a,"

g 28 AJ.4U, (20,000 cycles) < 1%

5

2 76K; self field

g& = tnviem

E25 "

oo 10 100 ©1000 10" 40%

Fatigue Cycles

Effect of fatigue cycling under transverse compres-
sive stress ina YBCO RABiTS sample laminated with
Cu foils on both sides (three-ply geometry). J, showed
no significant degradation under fatigue testing up to
20,000 cycles at 150 megapascals.



APPENDIX A:
CALIBRATION SERVICES

The Electromagnetics Division provides a number of for-fee calibration services for radio-
frequency and microwave standards. Below is a listing of those services conducted by the
division, with the technical contacts. More information can be found in the NIST Calibration
Services User’s Guide SP250, available from the Calibration Program at NIST, 301-975-2002,
calibrations@nist.gov, http://www.ts.nist.gov. The Web site provides a fee schedule.

THERMISTOR DETECTORS
Ron Ginley 303-497-3634

ScaTTERING PaRAmeTERs OF Passive Mutti-Port Devices
Ron Ginley 303-497-3634

THERMAL Noise MeasuremENTS
Dave Walker : 303-497-5490

Dietectric AND Macnetic MateriaL MEASUREMENTS
Jim Baker-Jarvis 303-497-5621

Microwave ANTENNA PARAMETER MEASUREMENTS
Katie MacReynolds 303-497-3471

FieLp STRENGTH PARAMETER MEASUREMENTS

Dennis Camell 303-497-3214

Information about the availability and shipping requirements for Electromagnetics Division
services may be obtained from Puanani DeLara, 303-497-5284.



ConTENTS

Welcome... wee oe
Introduction to Technical Programs
Electromagnetics Division Staff...

Radio-Frequency Electronics Group
Microwave Measurement Services
Micro/Nano Electronics ..............
Electromagnetic Properties of Materials

Radio-Frequency Fields Group
Antennas and Antenna Systems: Antenna Theory and Applications ..
Antennas and Antenna Systems: Antenna Near-Field Measurements
Antennas and Antenna Systems: Metrology for Radar Cross Section Systems...........24
Electromagnetic Compatibility: Reference Fields and Probes.......sssssssssssssssssersesesesene 26

Electromagnetic Compatibility: Complex Fields.....

Electromagnetic Compatibility: Time-Domain Fields
Magnetics Group

Magneto-Mechanical Measurements for High Current Applications ......------s+-- 33

Standards for Superconductor and Magnetic Measurements

Magnetodynamics
Spin Electronics .
Magnetic Devices and Nanostructures...
Microsystems for Bio-Imaging and Metrology.
Appendix A: Calibration Services .......
Appendix B: Postdoctoral Research Associateships.
Appendix C: Prefixes for the International System of Units (ST)
Appendix D: Units for Magnetic Properties......
Appendix E: Symbols for the Chemical Elements



to 96 gigahertz, with immediate plans to extend operation to 110 gigahertz. At this time, there is a very
large gap in frequency coverage between 110 gigahertz and infrared laser measurements. This region in
frequency space has an increasing number of applications in astronomy, biology, and homeland security
that will be enhanced by better power measurements. The exact approach we take to develop these new
power measurements will depend on developments in available equipment and the abilities of the appli-
cant. However, we anticipate that the new sensors will compare heat produced by millimeter-wave power
absorption and DC power absorption. One option is the development of a thin-film bolometer resistor.
The bolometer detects power through its change in resistance. The bolometer resistor will be thermally
isolated from the bulk of its substrate through micromachining techniques. An alternative approach will
be to develop a calorimeter that directly senses the temperature rise due to millimeter-wave absorption. A
wide range of microwave and millimeter-wave components, sources, and existing standards are available
as well as NIST’s in-house capabilities for making integrated circuits for research.

Quantum-Basep Microwave Amptitupe MEASUREMENTS
T. P. Crowley

This research opportunity will develop a technique for measuring microwave magnetic fields based
on quantum-mechanical principles. We have already performed a proof-of-concept experiment using a
set of laser-cooled cesium atoms in an atomic clock fountain apparatus. Rabi oscillations between two
hyperfine levels of the cesium ground state were measured to determine the RF magnetic field strength
in a resonant cavity. Our next step in this research is to improve the measurement accuracy by creating
an apparatus specifically designed for making measurements in a waveguide. Hither laser-cooled atoms
or a gas cell of cesium may be used. A DC magnetic field will be employed to vary the RF measurement
frequency. The goal of the new experiment will be to perform a comparison with traditional measurements
at accuracy comparable to the current state-of-the-art. Ultimately, we hope to develop a technique that is
applicable over a broad frequency range and can be used to characterize transfer standards. The research
is a fundamental change in the approach to measuring microwave signal levels. Traditional techniques
rely on the heating induced when microwave power is absorbed and are based on comparisons with DC
power measurements. Uncertainties are introduced because RF and DC power are not typically dissipated
in the same location. We hope that a quantum-based measurement will greatly improve the accuracy of
our primary standards and lead to new applications and techniques. Available resources will include a
laser system to perform the atomic measurements and a wide range of microwave components, sources,
and existing standards.

Noninvasive HicH-FREQUENCY NANOSCALE PRoBING, FIELD IMAGING, AND
Nanowire MEASUREMENTS
P. Kabos and J. R. Baker-Jarvis

Few experimental tools are currently available that can characterize and probe high-speed/frequency
properties of materials and devices on a nano/molecular scale. Proposals are invited for high-frequency
accurate noninvasive nanoscale probing and theory; electromagnetic field imaging; and measurements
of voltage, current, and materials properties. The objective is to develop the fundamental metrology;
the instruments and standards that will make it possible to perform high-speed voltage and current
measurements necessary for the characterization of high-speed, high-performance ultrahigh-density
nano- and molecular-electronic devices; and of the electromagnetic properties of nano-engineered,
artificial, nanowire, and carbon-nanotube-based materials and devices. Film deposition, lithography
and state-of-the-art microwave test systems, probe stations, and atomic force microscopy facilities are
available for the proposed research.

LINEAR AND NONLINEAR DamPiNG AND RELAXATION IN MAGNETIC INFORMATION
Storace Materiats
P. Kabos and S. E. Russek

As magnetic recording moves well into the gigahertz frequency regime, the mechanisms that limit the
precession dynamics and decay time of the spin system in magnetic thin films become limiting factors in



order to address these issues. Use of on-wafer measurements of thin-film devices allows us to measure
the impedance of planar thin-film-based structures at frequencies up to 100 gigahertz. When combined
with more traditional impedance analysis at lower frequencies, we can obtain frequency-dependent
impedance data over the extremely broad frequency range from several 100 hertz to 100 gigahertz. The
electrical impedance of planar measurement structures can be used to extract intrinsic material quanti-
ties, such as the conductivity or dielectric permittivity, of the constituent thin-film materials. Such mea-
surements techniques are applicable to a wide range of electronic thin-film materials, and are currently
being used to study thin-film material systems such as dielectrics, ferroelectrics and high-temperature
superconductors.

Microwave BIoELECTRONICS
J.C. Booth

Electromagnetic characterization can be a viable alternative to chemical or optical detection schemes to
analyze biological samples. An exciting new option in dielectric characterization is dielectric spectros-
copy: the measurement of a sample’s dielectric response across a very broad range of frequencies. This
technique has the potential to rapidly characterize a wide variety of biological materials, from macro-
molecules such as hemoglobin to live bacterial samples to proteins and DNA. By combining lithographi-
cally defined broadband microwave structures with microfluidic chambers produced by state-of-the-art
micromachining techniques, it is possible to determine the dielectric response of extremely small sample
volumes (picoliters) over 9 decades in frequency (100-hertz to 100 gigahertz). Integration with other
micro-electromechanical systems (MEMS), such as microfluidic pumps and circuits, could enable rapid
analysis of large numbers of different samples in high-throughput screening systems. Knowledge of the
dielectric properties of biological samples (e.g., tissue, blood) is also necessary for the development of
new microwave or millimeter-wave based medical treatments and/or diagnostics, and could also be applied
to determine the effect of electromagnetic signals at the cellular level. For example, such measurements
could provide valuable data on the possible health hazards posed by the proliferation of commercial
wireless devices. Currently, data on the dielectric properties of many biological substances, if existent,
are rarely available at frequencies above 20 gigahertz. By extending the frequency range for dielectric
analysis up to at least 110 gigahertz, we will create a new tool for characterizing and understanding the
interaction between organic materials and microwave radiation.

SupERCONDUCTOR CRITICAL CuRRENT DENSITY DETERMINATION BY
NonLINEAR Microwave RESPONSE

J.C. Booth

One of the fundamental properties of superconductors is the critical current density (J,), which sets the
upper bound for the current-carrying capacity of a superconductor. Our recent measurements of the non-
linear response of YBCO thin films have demonstrated good agreement with theoretical predictions for
nonlinear response due to pair-breaking in d-wave superconductors, and our measurement system yields
values for the pair-breaking current density that agree remarkably well with theoretical predictions of
this quantity for YBCO thin films. Our nonlinear measurement technique could provide an entirely new

|__path to determining critical current densities in superconductors, and will likely yield intrinsic J_ values
closer to theoretical predictions than conventional J, measurement techniques. We plan to apply this
measurement technique to experimentally determine the critical current density of YBCO, MgB,, Nb,
and other technologically important superconductor thin-film materials, and also to explore the role of
the symmetry of the superconducting energy gap on the nonlinear microwave response. In addition, we
will also explore the use of these reproducible nonlinear effects in superconductors to develop standard
devices to aid in the calibration of next-generation nonlinear measurement systems.

MILumeterR-Wave anp Microwave Power MeasureMeNnTS
T. P. Crowley

Research will be performed to develop power measurements at millimeter (mm) wave frequencies above
110 gigahertz. NIST currently operates microwave power standards at frequencies from 50 megahertz



HicH-Dynamic-Rance EvectricaL MEASUREMENT SYsTEMS
D. F. Williams, P. D. Hale, and K. A. Remley

The ability to characterize signals that cover a high dynamic range is becoming important for many
applications in both wireless and optoelectronics. Applications for high-dynamic-range measurement
systems are both diverse and of high impact. They include network impairment studies for broadband
wireless and optical networks, improved amplifier distortion measurements and models, detection of
weak signals, and analog to digital converter characterization. We anticipate these measurement systems
will also be useful in improving our traceability path for microwave phase standards. We wish to develop
high-dynamic-range electrical measurement systems with measurement bandwidths up to 50 gigahertz.
These new measurement systems will be based on a mixture of temporal sampling and frequency-domain
down-conversion schemes. A high priority will be establishing measurement traceability to our electro-
optic sampling system. This project will advance the state-of-the-art for electrical measurements and
includes a good mix of both theoretical and laboratory work.

On-Warer Microwave MEASUREMENTS AND STANDARDS
D. F. Williams and P. Kabos

Research opportunities exist for theoretical and experimental studies of wafer-level microwave measure-
ment techniques in the frequency range of 50 megahertz to 110 gigahertz. Work focuses on the on-wafer
measurement of S-parameters and signal characterization, including the development of new measure-
ment methodologies, and modeling and analysis of single and coupled planar transmission lines. Unique
opportunities exist to compare both the theoretical and experimental results.

Precision HicH-SpeeD Waverorm MEASUREMENT
D. F. Williams and P. D. Hale

We have developed an electro-optic sampling system that measures very fast electrical waveforms. This
project will extend our current electrical models for the measurement system to 400 gigahertz and allow the
precision measurement of waveforms with 5 ps rise times. We have constructed an electro-optic sampling
system with a measurement bandwidth near one terahertz. The system is designed to accurately measure
electrical pulses on transmission lines printed on special NIST-constructed electro-optic substrates, and
now provides NIST’s most fundamental measurements of high-speed electrical pulses. This system is
now being used to calibrate the output of high-speed photodiodes and oscilloscopes to 110 gigahertz.
Distortion in the probes we use to inject electrical signals onto the electro-optic substrate currently limits
our measurement bandwidth to 110 gigahertz. This project will focus on using data from the electro-optic
sampling system itself to characterize these probes to 200 gigahertz and beyond. The result of the effort
will be models for the probes that will allow us to break our current 110 gigahertz measurement barrier
and characterize the fastest photodiodes, pulse sources, and oscilloscopes in the world.

Uttrarast SicNaL Measurement FOR HicuH-SPeep INTEGRATED CiRcuITS

D. F. Williams, P. Kabos, P. D. Hale, and T. S. Clement

We study methods for measuring and calibrating ultrafast signals with 110 gigahertz to 400 gigahertz
bandwidths on high-speed integrated circuits. Methods that we are currently investigating include the use
of electro-optic interactions with bandwidths of many terahertz. Research focuses on fully calibratable
measurement of signals in printed transmission lines with low uncertainty, extension of measurements
to 110 gigahertz in the near future, and extension to 400 gigahertz in the next five years.

FuNDAMENTAL MopELING FOR ELECTROMAGNETIC CoMPATIBILITY
C. L. Holloway and D. A. Hill

Analytic and numerical theoretical investigations are needed on a broad range of topics related to electro-
magnetic compatibility EMC) and electromagnetic interference (EMI). The particular numerical models
of interest are finite-difference time-domain, finite-elements, integral equations, and hybrid techniques.



introducing conducting fibers; however, this may
affect mechanical performance. There is a need to
reliably measure the EM shielding properties of
advanced composites so that manufacturers can find
the right balance between electrical and mechani-
cal performance for a particular application. We
are investigating the use of nested reverberation
chambers for this purpose. We are investigating
' better statistical descriptors for the shielded fields
| to more accurately define shielding effectiveness

i in complex coupling environments.

| With the proliferation of wireless devices in recent
years, there is a growing need to test the opera-
tion and functionality of these various devices in
; different multipath environments, ranging from
| line-of-sight environment to a pure Rayleigh envi-
ronment. We have recently shown how a reverbera-
tion chamber can be used to generate a variable
K-factor propagation environment for the testing
of wireless communications devices. It was shown
that by judiciously changing the characteristics
of the reverberation chamber and/or the antenna
configurations in the chamber, any desired Rician
K-factor (that is, any desirable Rician multipath
propagation environment) could be achieved. We
have developed two different approaches, the first
based on one transmitting antenna, and the second
based on two transmitting antennas. Reverberation
chambers represent reliable and repeatable test
facilities that have the capability of simulating
any Rician multipath environment for the test-
ing of wireless communications devices. Such
a test facility will be useful in the testing of the
operation and functionality of the new emerging
wireless devices in the future. Our paper on this
topic was published in November 2006 issue of
IEEE Transactions on Antennas and Propagation.
In it, we laid out the framework, presented a few
simple expressions, and presented experimental
evidence to support the possibility of using rever-
beration chambers for testing of wireless devices
in different Rician multipath environments. Not

—alLmnultipath_envirouments-can_be-characterized_—_} P

by a Rician distribution. An example would be an
environment where both scattering components and
multiple direct components are present. In such an
environment, the direct coupling components have
different amplitudes and phases (or different Dop-
pler shifts). Such environments could in principle
be simulated in reverberation chambers in which
several transmitting antennas are used. The use of
reverberation chambers in these other multipath
environments is the topic of future work.

First responders need reliable communications
in emergency scenarios. Disaster scenarios and
terrorist attacks may result in scenarios where
responders or citizens are trapped in collapsed
or blocked buildings. The propagation of signals
in the bands used by first-responder radios and
cellular telephones needs to be investigated. We
have performed unique experiments to define com-
munications links in buildings prior, during, and
after demolition. These data will give invaluable
insight into the communications problems faced
by first responders.

Metamaterials (that is, engineered or man-made
materials) have generated considerable interest in
recent years. Metamaterials are commonly engi-
neered by arranging a set of scatterers throughout
a region of space in a specific pattern so as to
achieve some desirable bulk behavior. Examples
of electromagnetic metamaterials are artificial
dielectrics, photonic bandgap structures, and
frequency-selective surfaces. Recently there have
been studies on the properties and potential appli-
cations of double-negative (DNG) materials. We
are investigating a composite medium consisting
of insulating magneto-dielectric spherical particles
embedded in a background matrix to achieve
DNG behavior. We have shown that the effective
permeability and permittivity of the mixture can
be simultaneously negative for wavelengths where
the spherical inclusions are resonant.

We work closely with national and international
standards bodies to transfer experimental and
theoretical results and to improve test methods
for large, complex systems. We plan to continue
participation in various IEC, CISPR, ANSI, SAE
and IEEE standards committees related to EMC

test methods.

Division staff members map signals from transmitters
buried in a collapsed building.



J. Randa, S. L, Sweeney, T. McKay, D. K, Walker, D. R.
Greenberg, J. Tao, J. Mendez, G. A. Rezvani, and J. J. Pekarik,
“Interlaboratory Comparison of Noise-Parameter Measurements
on CMOS Devices with 0.12 pm Gate Lengt,” 66th ARFTG
Microwave Measurements Conf. Digest, Washingtou, DC,
December 2005, pp. 77-81.

J. Verspecht, D. F. Williams, D. Schreurs, K. A. Remley, and
M. D. McKinley, “Linearizing Large-Signal Scattering Func-
tions,” JEEE Trans. Microwave Theory Tech. 53, 1369-1376

(May 2005).

E. Gerecht, D. Gu, S. ¥ngvesson, F, Rodriguez-Morales, R.
Zannoni, and J. Nicholson, “HEB Heterodyne Focal Plane Ar~
rays: A Terahertz Technology for High Sensitivity Near-Range
Security Imaging Systems,” Proc. SPIE Defense and Security
Symposium, Orlando, FL, March 2005, pp. 149-160.

A. Slavin and P. Kabos, “Approximate Theory of Microwave
Generation in a Current-Driven Magnetic Nanocontact Mag-
netized in an Arbitrary Direction,” IEEE Trans. Magn. 41,
1264-1273 (April 2005).

D.F, Williams, P. D. Hale, T. S. Clement, and J. M. Morgan,
“Calibrated 200 GHz Waveform Measurement,” JEEE Trans.
Microwave Theory Tech. 53, 1384-1389 (April 2005).

F. Rodriguez-Morales, K. S. Yngvesson, E. Gerecht, N. Wade-
falk, J. Nicholson, D. Gu, X. Zhao, T. Goyette, and J. Waldman,
“A Terahertz Focal Plane Array Using HEB Super-Conducting
Mixers and MMIC IF Amplifiers,” IEEE Micro. Wireless Comp.
Lett. 15 199-201 (April 2005).

W.L, Johnson, $. A. Kim, 8. E. Russek, and P. Kabos, “Bril-
louin Light Scattering From Pumped Uniform-Precession
and Low-k Magnons in Ni, Fe,,, Appl. Phys. Lett. 86, 102507
(March 2005).

J.R. Baker-Jarvis, M. D. Janezic, B. F. Riddle, R. T. Johnk, C.
L. Holloway, R. G. Geyer, and C. A. Grosvenor, “Measuring
the Permittivity and Permeability of Lossy Materials: Solids,
Liquids, Metals, and Negative-Index Materials,” NIST Techni-
cal Note 1536 (February 2005).

T.M. Wallis, J. Moreland, B, Riddle, and, Kabos, “Microwave
Power Imaging with Ferromagnetic Calorimeter Probes on
Bimaterial Cantilevers,” J. Magn. Magn. Mater. 286, 320-323
(February 2005),

K. A. Remley, D. F. Williams, D. Schreurs, and J. Wood,
“Simplifying and Interpreting Two-Tone Measurements,” EEE
Trans. Microwave Theory Tech, 52, 2576-2584 (November
2004).

K. A. Remley, D. Schreurs, D. F, Williams, and J. Wood,
“Extended NVNA Bandwidth for Long-Term Memory Mea-
surements,” Proc. IEEE MTT-S Int. Microwave Symp., pp.
1739-1742 (June 2004).

E. Gerecht, D. Gu, X. Zhao, J. Nicholson, F. Rodriguez-Morales,
and 8. Yngvesson, “Development of NbN THz HEB Mixer
Coupled Through SlotRing Antennas,” Proc. 15th Symp. Space
Terahertz Technology, Northampton, MA, April, 2004.

P. Kabos, U. Arz, and D. F. Williams, “Multiport Investigation
of the Coupling of High Impedance Probes,” JEEE Microwave
Wireless Comp. Lett. 14, 510-512 (2004).

J. Baker-Jarvis, P. Kabos, and C. L. Holloway, “Nonequilibrium
Electromagnetics: Local and Macroscopic Fields and Constitu-
tive Relationships,” Phys. Rev. E 70, 036615 (2004).

J. Randa and D. K. Walker, “Amplifier Noise-Parameter Mea-
surement Checks and Verification,” 63rd ARFTG Conf. Digest,
Ft, Worth, TX, pp. 41-45 (2004).



Setup for the 13.56 megahertz load modulation test, which is used to test the strength of the return signal from an
RFID card.

um RFID Test Bed — An RFID test bed has been
established at 13.56 megahertz for testing RFID
cards for load modulation (return signal strength)
and electromagnetic durability when the cards are
exposed to electric discharge or to high strength
alternating electric and magnetic fields.

SHorT Courses

NIST and the Georgia Institute of Technology
annually offer an introductory course on antenna
measurements. Every other year NIST presents an
in-depth technical course restricted to near-field
methods that were pioneered at NIST.

SortTwaRE

Planar, cylindrical, and spherical near-field scan-
ning applications algorithms are currently available.
Probe position-correction software is available for
the planar and spherical methods. The constrained
least squares algorithm for partial sphere data is
also available. Quiet-zone evaluation and imaging
programs will be available soon.

EXTERNAL RECOGNITION
mu Mike Francis chairs the Antenna Standards

Committee of the IEEE Antennas and Propaga-
ion Soci

REcENT PuBLICATIONS

J.R, Guerrieri, M, H. Francis, P. F. Wilson, A. B. Kos, L.
E, Miller, N. P. Bryner, D. W. Stroup, and L. Klein-Berndt,
“RFID-Assisted Indoor Localization and Communication for
First Responders,” Proc. Antenna Measurement Techniques
Association (AMTA), Austin, TX (October 2006); Proc. Euro-
pean Conference on Antennas and Propagation, Nice, France
(November 2006).

L.E. Miller, P. F. Wilson, N. P. Bryner, M. H. Francis, J. R.
Guerrieri, D. W. Stroup, and L. Klein-Bemdt, “RFID-Assisted
Indoor Localization and Communication for First Respond-
ers,” Proc. 2006 Intl. Symp. Advanced Radio Tech. (ISART),
Boulder, CO, pp. 83-91 (March 2006).

M.H. Francis, K, MacReynolds, and J. R. Guerrier, “Compari-
son of Gains Determined from the Extrapolation and Far-Field
Pattern Integration Methods,” Proc. Antenna Meas. Tech. Assoc.
(AMTA), Newport, RI, pp. 304-307 (November 2005).

R. C. Wittmann, A. E. Cox, and R. H. Direen, “Proximity
Effects in the Calibration of Microwave Radiometers,” Proc.
‘Antenna Meas. Tech. Assoc. (AMTA), Newport, RI, pp. 333-
336 (November 2005).

J. Guerrieri, K. MacReynolds, M. Francis, R. Wittmann, and
D. Tamura, “Practical Implementation of Probe-Position Cor-
rection in Planar Near-Field Measurements,” Proc. Antenna
Meas. Tech. Assoc. (AMTA), Atlanta, GA, pp. 356-359 (Oc-
tober 2004).

M. Francis, J. Guerrieri, K, MacReynolds, and R. Wittmann,
“Estimating Multiple-Refiection Uncertainties in Spherical
‘Near-Field Measurements,” Proc. Antenna Meas. Tech. Assoc.
(AMTA), Atlanta, GA, pp. 85-87 (October 2004).

m Mike Francis has been appointed to the An-
tenna Centre of Excellence (European Union)
Scientific Council for 2006 and 2007.

um Mike Francis received the Antenna Measure-
ment Techniques Association Distinguished Ser-
vice Award in October 2004.

R. Wittmann and M, Francis, “Spherical Scanning Measure-
ments: Propagating Errors Through the Near- to Far-Field
Transform,” Proc. Antenna Meas, Tech. Assoc. (AMTA),
Atlanta, GA, 74-79 (October 2004).

R. Wittmann, B, Alpert, and M. Francis, “Near-Field Spherical-
Scanning Antenna Measurements with Nonideal Probe Loca-
tions,” IEEE Trans. Ant. Prop. 52, 2184 (August 2004).



composites will be necessary. Needs for on-chip
microscale-to-nanoscale measurements of permit-
tivity and permeability have been highlighted by
the microelectronics industry.

TECHNICAL STRATEGY

The program’s main thrusts are in the areas that
support homeland security, biotechnology, mi-
croelectronics industry, and nanoscale metrology.
To support the microelectronics industries in their
quest for lower-loss materials, we will develop
higher frequency measurement methods and broad-
en our measurement temperature range with added
humidity control. Current research materials under
study are liquids, thin films and printed wiring
boards, low-loss dielectrics, magnetic crystals, and
synthetically polarized films.

To support the nanotechnology and artificial
material efforts, we will develop metrology for
nanoscale composites and advanced materials
such as metamaterials, multiferroics, thin films,
superconductors, and ferroelectrics. We have an
on-going effort focused on determining the permit-
tivity and permeability of thin-film samples that are
difficult to measure accurately with conventional
cavity-based microwave measurement techniques.
Material systems of interest are ferroelectric thin
films and multiferroic materials, which display
different properties depending on the application
of an electric- or magnetic-field bias. Also of inter-
est are thin-film materials that display relaxation
behaviors within the broad frequency range of our
measurement systems,

Tn order to understand the underlying physics of our
novel material measurements, we plan to have an
ongoing theoretical modeling effort that supports
the interpretation of our broadband spectroscopy
measurements.

In response to homeland security needs at airports,
we will perform research on the identification of
liquids from relaxation spectrum measurements.

This research is presently funded through the NIST —Seneration-ané

Office of Law Enforcement Standards.

In response to a need from the microelectronics
industry for on-chip characterization, we will ex-
tend our evanescent probe system to incorporate a
dielectric resonator, enhance our theoretical model,
and perform measurements on relevant materials.

We will also aid the PWB and LTCC industries in
measuring the permittivity of substrates at high
frequencies. To this end, we will further enhance
our wideband, variable-temperature metrology and
extend the capability of our Fabry-Perot measure-
ment system to include variable temperatures.

To aid the semiconductor industry for materials
characterization we will measure a wide spectrum
of semiconductor materials commonly used in the
electronics industry as a function of temperature
and frequency.

To satisfy documented needs in the health care,
biotechnology, and metal-detector industries, we
will characterize materials that simulate the elec-
trical properties of the human body. In addition,
in support of the biotechnology industry, we will
improve our liquid measurement metrology and
will compare our measurements with those of the
U.K.’s National Physical Laboratory, using the
liquid measurement methods we have developed.

To enhance the understanding of the physics of
high-frequency losses in dielectrics, we will test
ferroelectrics and crystals over wide temperature
and frequency ranges using an in-house model
for determination of the permittivity. We will
also compare the measured losses as functions of
temperature and frequency to expressions in the
solid-state literature.

We will support the development of high-frequency
standards by attending and contributing to IPC and
IEEE standards committee meetings.

In order to investigate the possible applications
of nonlinear permittivity effects we will study
nonlinear material responses. Nonlinear materials
are finding increased use in electronic applica-
tions. Examples include the use of ferroelectric
materials as voltage-controlled components and
high-temperature superconductors in high-order,
low-loss filter applications. Such nonlinear materi-
als invariably give rise to effects such as harmonic

intermodulation-distortion, which.
can have important consequences at the system
level. We will address these problems by evaluat-
ing the nonlinear response of broadband device
structures, in order to determine the intrinsic
nonlinearity of materials such as ferroelectrics and
high temperature superconductors.



AccOMPLISHMENTS

m= Phantom Study — The electric field statistics
in a heavily loaded reverberation chamber were
evaluated and compared to the empty-chamber
statistics. The load consisted of phantoms (water
bottles) filled with tissue-simulating liquid. Whole-
body average specific absorption rate (SAR)
in the phantoms was also determined via direct
measurements of temperature increase and indirect
measurements of insertion loss. The results sup-
port the use of a reverberation chamber for animal
exposure studies.

a Propagation in Collapsed Buildings —
Three experimental studies on signal propagation
in buildings prior, during, and after demolition
were completed. These experiments provide in-
valuable data on first-responder communication
challenges.

a Effective Boundary Conditions — Effective
boundary conditions for thin films with applica-
tions to active materials such as frequency-tunable
surfaces have been derived and published.

m= = Equivalent-Layer Models — Three equiva-
lent-layer models were developed for the electro-
magnetic characterization of carbon fiber compos-
ites used on aircraft.

REcENT PuBLIcATIONS

C. L. Holloway, G. Koepke, D. Camell, K. Remley, and S.
Schima, “Shielding and Attenuation Properties of Large Build-
ings and Structures,” Proc. 2006 EMC Europe Conf., Barcelona,
Spain, pp. 465-469 (September 2006).

J. Coder and John Ladbury, “Cable Shielding Measurements
Based on a Reference Unshielded Cable, or, Do You Really
Want to Base Your Results on a Naked Cable?” Proc. 2006 IEEE
Int. Symp. Electromagnetic Compatibility, Portland, OR, paper
WE-AM-I-7 (August 2006).

D. Love, J. Ladbury, and E. Rothwell, “Comparing Numerical
and Experimental Results for the Shielding Properties of a Dou-
bly-Periodie Array of Apertures in a Thick Conducting Screen,”
Proc. 2006 IEEE Int. Symp. Electromagnetic Compatibility,
Portiand, OR, paper TH-PM-1-2 (August 2006).

C. L. Holloway, G. Koepke, D. Camell, K. A. Remley, S.
Schima, and R. T. Johnk, “Propagation and Detection of Radio
Signals Before, During and After the Implosion ofa Large Con-
vention Center,” NIST Technical Note 1542 (May 2006).

C.L. Holloway, D. A. Hill, J. M. Ladbury, and G. H. Koepke,
“Requirements for an Effective Reverberation Chamber: Un-
loaded or Loaded,” JEEE Trans. Electromagn, Compat. 48,
187-194 (February 2006).

C. L. Holloway, M. A. Mohamed, E. F. Kuester, and A. Dien
stfiey, “Reflection and Transmission Properties of a Metafilm:
With an Application to a Controllable Surface Composed of
Resonant Particles,” IEEE Trans. Electromagn. Compat. 47,
853-865 (November 2005).

C. L. Holloway, M. S, Sarto, and M. Johansson, “Analyzing
Carbon Fiber Composite Materials with Equivalent-Layer
Models,” IEEE Trans, Electromagn, Compat. 47, 833-844
(November 2005).

C.L. Holloway, G. H. Koepke, D. G. Camell, K.A. Remley, D.
Williams, 8. Schima, and S. Canales, “Propagations and Detec-
tion of Radio Signals Before, During and Aer the Implosion of
a Large Sports Stadium (Veterans’ Stadium in Philadelphia),”
NIST Technical Note 1541 (October 2005).

C, L. Holloway, G.H. Koepke, D. G. Camell, K. A. Remley, D.
Williams, 8. Schima, 8. Canales, and D. T. Tamura, “Propaga-
tion and Detection of Radio Signals Before, During and After the
Implosion of a 13 Story Apartment Building,” NIST Technical
Note 1540 (May 2005),

M. Johansson, C. L. Holloway, and E. F. Kuester, “Bffective
Electromagnetic Properties of Honeycomb Composites, and
Hollow-Pyramidal and Alternating-Wedge Absorbers,” IEEE
‘Trans. Ant, Propagat., 53, 728-736 (February 2005).

J. Baker-Iatvis, P. Kabos, and C. L. Holloway, “Nonequilibrium
Electromagnetics: Local and Macroscopic Fields and Con-
stitutive Relationships,” Phys Rev E 70, 036615 (September
2004),

P, Wilson, “Test Object Electrical Size and Its Implication on
Pattern Sampling,” Proc. 2004 IEEE Int. Symp. Electromagnetic
Compatibility, Santa Clara, CA, pp. 349-352 (August 2004).

ors



next-generation and broadband wireless system
technologies, as well as broadband systems utilized
by first responders to emergencies. The project is
also involved in development of test signals that
will provide easier calibrations for wireless system
measurements.

Besides the characterization of noise at terahertz
frequencies, we are also focusing on applications
of passive terahertz imaging. Terahertz radiation
can penetrate clothing and, to some extent, can
also penetrate biological materials. Because of their
shorter wavelengths they offer higher spatial reso-
lution than microwaves or millimeter-waves. This
project focuses on developing the critical metrology
necessary to characterize newly developed terahertz
devices and systems that are coming to market.

AccomPLISHMENTS

m High-Frequency Nanodevice Metrology
—The primary focus is the development of metrol-
ogy for high-frequency scanned-probe microscopy
and micro-electromechanical systems (MEMS)
with submicrometer resolution. Specifically, this
includes the areas of quantitative high-frequency
imaging, measurement of electromagnetic field
components, and characterization of materials
that are incorporated into nanoscale electrical and
magnetic devices.

In order to investigate the high-frequency response
of nanoscale structures such as carbon nanotubes
and Si-based nanowires, we constructed a univer-
sal scanning probe station that can operate as a
RF-STM probe, near-field scanning probe, AFM.
probe, or a high-impedance, noncontacting probe
with nanometer spatial positioning at frequencies
up to 50 gigahertz.

For more accurate measurements of electromag-
netic field components, we designed a three-layer
SiN/SiO/SiN cantilever probe for high-frequency
calorimetric field imaging and showed a demon-
strable improvement in performance and yield
over traditional two-layer micro-electromechanical
system (MEMS) calorimetric probes.

Investigating the Einstein-de Hass effect, we de-
veloped a MEMS-based approach to measuring the
magneto-mechanical ratio g", a critical parameter
for the development of materials for spin electron-
ics and magnetic data storage.

We demonstrated that calibrated on-wafer tech-
niques can be employed to characterize the
broadband frequency response of high-impedance
devices such as multiwalled carbon nanotubes as
well as quantify the effect of contact resistances,

A multi-wall carbon nanotube welded across a gap in
the center conductor of a coplanar waveguide.

0 5 10 18 20
Frequency (GHz)

Admittance (which includes conductance) in millisie-
mens as a function of frequency in gigahertz at the
left contact of the carbon nanotube, Data were taken
with illumination of the nanotube on and off. The
admittance is calculated from scattering parameters
measured with a network analyzer.

mu High-Speed Waveform Metrology — Sales
in the high-speed telecommunications market are
based on the ability to deliver high-speed, reli-
able, and interoperable communication systems
with greater information-carrying capacity and
at a lower cost. Integrated digital and microwave
electronics now require bandwidths in excess of
110 gigahertz, larger than can be supported by
current coaxial connectors. To meet these demand-
ing needs, we are developing both 110 gigahertz
coaxial waveform metrology, as well as on-wafer
metrology to even higher frequencies. Our cur-
rent focus includes design of a 400 gigahertz
opto-electronic source, integration of this source
into a microwave probe, and construction of an
electro-optic measurement system to characterize
the bandwidth of this source.





recording head design, materials selection, and magneto-electronics applications. Low- and high-power
ferromagnetic resonance (FMR), microstripline FMR, off-resonance effective linewidth techniques, and
Brillouin light scattering provide critical tools needed to elucidate these processes and develop optimum
thin-film materials for these applications. In this program, metallic thin materials, metal-oxide multilayers,
and nano-oxide films will be fabricated and used for research on the fundamental loss processes that limit
magnetic switching and large-angle precession dynamics response times. Effectively all of the established
tools of high-frequency magnetics research will be used on this topic. The use of FMR techniques over
a wide range of frequencies from 1 to 100 gigahertz and different static and pumping field geometries
will help separate intrinsic loss processes (e.g., magnon-electron scattering) from extrinsic processes
(e.g., two-magnon relaxation). Effective linewidth and spin-wave instability measurements will be used
to probe the wave vector dependences of the intrinsic processes. High-power above-threshold spin-wave
instability, Brillouin light scattering, and FMR force microscopy techniques will give new information
on the actual nonlinear response of these film materials systems. This program will utilize facilities and
capabilities developed at both NIST and in the laboratory of Professor Carl Patton at Colorado State
University.

THERMAL Noise MeasuREMENTS
J. Randa

Theory, standards, methods, and systems are developed for highly accurate measurements of thermal
electromagnetic noise from radio frequencies to terahertz waves. Current research comprises two major
thrusts: developing improved methods for characterizing the noise properties of low-noise amplifiers
and transistors, and developing systems and methods for noise measurement at terahertz frequencies.
Research opportunities are supported by extensive theoretical and experimental expertise, as well as
world-class noise-temperature measurement capabilities.

MetroLocy For WirELess Systems
K. A. Remley

President Bush has called for broadband access for all Americans by 2007. Wireless plays an increasing
role in this area. Globally, wireless revenue as a whole will approach almost 49 percent of all telecom-
munications services revenue (some $1.2 trillion) by the end of 2006, largely spurred by broadband.
Broadband access using wireless technology requires complicated modulation formats and broad modu-
lation bandwidths to maintain spectral efficiency. It is difficult to verify the performance of electrical
measurements instrumentation for broadband wireless systems, since these instruments are currently at
the cutting edge of measurement technology. In some cases, this leads to a “chicken and egg” dilemma
for the wireless test industry. For example, a broadband source may be used to characterize a receiver,
which is then used to characterize the source. While new hardware development will play an important
role in solving the broadband measurement issue, completely new, technically sound measurement
procedures and metrics are also needed to verify broadband system performance. Development of such
measurement techniques will be the focus of the project The work will provide a good mix of theoretical
development and hands-on experiment in an area of intense commercial growth.

CHARACTERIZATION OF HIGH-SPEED DIGITAL INTERCONNECTS AND SIGNALS
D. F. Williams, P. Kabos, P. D. Hale, and T. S. Clement

This project provides unique opportunities for theoretical and experimental studies of high-speed digi-
tal interconnects and signals. Current research focuses on adapting microwave measurement methods
to noncontacting characterization of high-speed signals and the characterization of conventional, dif-
ferential, and coupled differential transmission lines fabricated on silicon substrates. This research has
strong relevance to industry, and collaborators will have access to measurement equipment at frequencies
beyond 110 gigahertz. .



have been fabricated by electron-beam lithography
to study their suitability for magnetic media. The
nanodots are fabricated from multilayers of Co
and Pd either using sputtering or molecular beam
epitaxy. The perpendicularly magnetized nanodots
have switching fields that range between 0.5 and
1.5 teslas. The switching field distributions were
measured for both polycrystalline and epitaxial
structures with a variety of underlayers to deter-
mine the effect of the microstructure on switching.
The key results were the observation of a very
narrow switching distribution in nanodots with
Ta underlayers and that the epitaxial structures
did not show significantly narrower switching
distributions than the polycrystalline structures.
This study shows that the polycrystalline nature of
the nanodots, which affects both the magnetic and
lithographic uniformity, is not responsible for the
variation in observed switching properties.

Magnetic force microscope image of 100-nanometer
nanodots showing partial magnetic switching. Each
nanodot is a stack of 8 layers of 0.35 nanometer of Co
alternating with 8 layers of 1.02 nanometers of Pd.

mu Evaluation of Fe, for use as an MRI contrast
agent — In collaboration with the University of
Colorado, we completed a study of the potential use
of Fe, molecular nanomagnets as an MRI contrast
agent. NMR relaxivity data were obtained over a
broad range of concentrations. At low concentra-
tions the relaxivity, which is proportional to MRI
contrast, was shown to be comparable to that of
existing contrast agents. At high concentrations the
relaxivity decreased. Based on a SQUID magne-
tometer evaluation of the decomposition of Fe, in
aqueous solutions, the concentration dependence
of the relaxivity was attributed to the concentration
dependence of the decomposition rate. The excita-

tion spectra of Fe, were characterized using SQUID
high-frequency EPR. This novel EPR technique
uses a SQUID magnetometer to quantitatively mea-
sure the spin excitation in response to microwave
radiation. This work is our first effort to correlate
the ESR fluctuation spectrum of a nanomagnet to
the NMR relaxivity.

Iron-8 (Feg) Macro-Spin Molecule
S=10

5 electrons
S=52 oy

— — 15nm ———>

Fe, nanomagnets, Each Fe** ion has spin 5/2; 6 are
Serromagnetically aligned and 2 are antiferromagneti-
cally aligned. The net macro-spin is 10.

© Feb
= Magnevist
425.7 s"'mM

e| 1, =5.48"'mut

0 T
t) 1 2 3 4

Concentration (mM)

Longitudinal relaxivity of Fe, as a function of concen-
tration.

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MRI phantom with multiple nanomagnetic contrast
agents.

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1



Rapvio-FREQUENCY FieLps Group

Perry Wilson, Group Leader.....
Ruth Marie Lyons, Secretary ....
AANTENNA THEORY AND APPLICATIONS

Michael Francis, Project Leader
Lorant Muth

Randal Direen, Research Associat
/ANTENNA Near-Fietp MEASUREMENTS

Katie MacReynolds, Project Leader ....-3471
Jeffrey Guerrieri
Doug Tamura..

Carl Stubenrauch,
Research Associate

REFERENCE FIELDS AND PROBES

Perry Wilson, Project Leader.
Dennis Camell

REFERENCE FIELDS AND PRroses (CONTINUED)

David Novotny.. 3168
Keith Masterson, Research Associate..-3756

Compcex Fietps

Galen Koepke, Project Leader............. -5766
Christopher Holloway
John Ladbury.........
Jason Coder, Research Associate
David Hill, Research Associate.
Ed Kuester, Research Associate.
William Young, Research Associate ....-4649

Time-Domain Fietps

Robert Johnk, Project Leader
Chriss Grosvenor

Macnetics Group

Ron Goldfarb, Group Leader
Ruth Corwin, Secretary....

Macneto-MeEcHanicat MEASUREMENTS FOR
HicH Current Apptications

Jack Ekin, Project Leader
Cam Clickner .
Najib Cheggour, Research Associate.

Danko van der Laan,
Research Associate.........esssssssesssees -4702

STANDARDS FOR SUPERCONDUCTOR AND
Maenetic Measurements

Loren Goodrich, Project Leader .......... -3143
Ted Stauffer, “3777

Macnetopynamics

Tom Silva, Project Leader.
Tony Ko:
Mark Hoefer, Research Associate

Spin ELectronics

Bill Rippard, Project Leader...
Matt Pufall, Research Associate
Mike Schneider, Research Associate ...-4203

Maenetic Devices anp NANosTRUCTURES

Stephen Russek, Project Leader...........
Brant Cage, Research Associate .
Justin Shaw, Research Associate.

Microsystems For Bio-IMAGING AND
METROLOGY

John Moreland, Project Leader
Li-Anne Liew, Research Associate.
Gary Zabow, Research Associate.
Wendy Krauser, Graduate Student

Dan Porpora, Graduate Student...........



:

We will provide technical information and guid-
ance to standards organizations to help correlate
measurements between various EMC test facili-
ties. We will also cooperate with the national test
laboratories of our international trading partners
to perform round-robin testing and comparison of
various standard antennas and probes. This assures
international agreement in their performance and
reduces the uncertainties in the areas of metrology
that affect international trade.

ACCOMPLISHMENTS

= Probe Calibrations — Calibrations were per-
formed on probes/antennas for several companies
and/or government agencies covering the frequency
range of 10 kilohertz to 45.5 gigahertz by use of
TEM cell and anechoic chamber test facilities. Field
levels varied from 1 to 200 volts per meter.

= Co-Conical Field Generation System
(CFGS) —A 10 megahertz to 40 gigahertz RF
probe test facility for the U.S. Air Force is nearing
completion. The final machining of the test cell was
completed in July 2006 and delivered to NIST for
testing and full system integration. The CFGS is
made of two major subsystems. The first is a har-
monically pure RF generating system capable of
producing 25 watts of RF power out of a single RF
connector from 10 megahertz to 40 gigahertz. This
subsystem involved the design of new RF compo-
nents that are now standard product offerings from
two companies. The power delivery subsystem
feeds the power into the second subsystem: a broad-
band TEM transmission system and termination
that can generate high-intensity fields and calibrate
probes faster, and with comparable uncertainties,
than conventional anechoic chambers.

Co-conical field generation system being assembled at

NIST in preparation for delivery to the U.S. Air Force.
The height of the cone is 3 meters.

m Electric and Magnetic Field Probe — A loop
antenna with integrated photonics and controls
to simultaneously measure electric and magnetic
fields at levels up to 1 kilovolt per meter has been
developed.

REcENT PuBLicaTIONS

C.L. Holloway, P. F. Wilson, and R. F, German, “The OATS
Method Revisited,” JEEE EMC Newsletter, pp. 41-43 (August
2005).

J. Hamilton and K. Masterson, “Accurate Bias Point Control
for an Electrically Isolated Mach-Zehnder Interferometric
Modulator Via an Analog Optical-Fiber Link,” Proc. SPIE,
Denver, CO, 5531, 323-331 (August 2004).

P. Wilson, C. Holloway, and G. Koepke, “A Review of Dipole
Models for Correlating Emission Measurements Made at
Various EMC Test Facilities,” Proc, 2004 IEBE Int. Symp.
Electromagnetic Compatibility, Santa Clara, CA, pp. 898-901
(August 2004).



=

particular, we followed a previous formalism that
includes interface roughness (interdiffusion length
of different atoms) for predicting the oscillation
periods of interlayer magnetic exchange coupling
of Fe/Cr/Fe thin film multilayers as a function of
Cr spacer thickness. Our results indicate that the
magnetometer is well suited for studying the subtle
changes in the magnetic moment of multilayer films
during film growth. Specifically we determined the
short and long period oscillation wavelength of the
interlayer exchange coupling in the Cr layer to be
2.1 monolayers and 13.8 monolayers, respectively.
These results illustrate the utility of MEMS mag-
netometers for studying ultrathin magnetic films
and multilayer devices.

Custom cantilever assembly for submonolayer in-situ
magnetometery of multilayer films (front and back
views). The paddle is I millimeter on a side.

0.50

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&

T

—
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4
p
4
r
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2
8
8

ke

Magnetic moment ( nAm 2)

2
3
Be

e
3
8

o12 3 4 5 67 8 9 1011121314 15
Cr thickness (ML)

Graph of experimental magnetic interlayer exchange
coupling measured by the micro-resonator magnetom-

from the fluid bead solution. The particles are
confined by local magnetic field gradients in an
array of magnetic spin-valve structures. The spin
valves have a bistable ferromagnetic “on” and
antiferromagnetic “off” net magnetization states in
the absence of an externally applied magnetic field,
which allows magnetic particles to be selectively

confined or released for transport or sorting.

Single particles can be rotated by applying a global
magnetic field, and thus, the platform may be
potentially used as a magnetic molecular tweezer
where particles are rotated about the x, y or z axes
while attached to multiple points of a biological
molecule such as the ends of a strand of DNA to
impart torsional forces. Alternatively, spin-valve
trap arrays can be adapted to a low power MRAM
switching architecture for massively parallel
particle sorting applications. Previous work with
spin-valve trapping elements in terms of biological
microfluidic applications focuses on their ability to
detect the presence of magnetic particles as they
attach to locations with specific biological antibod-
ies. In contrast, the current platform incorporates
spin-valve elements that can be switched between
bistable states to provide a local magnetic field
gradient sufficiently large to trap a magnetic par-
ticle that can be used not only for the purpose of
investigating conformational dynamics of single
biological molecules but also to capture and sort
biological molecules for gene sequencing or bio-
assay applications.

PlGF as a fametion of Cr layer thickness.

= Manipulation of Magnetic Particles by Pat-
terned Arrays of Magnetic Spin-Valve Traps
— To address some of the limitations of current
single-molecule tweezers techniques, we developed
a novel magnetic tweezers based on a chip-scale
microfluidic platform that can trap, measure, ma-
nipulate and sort magnetic particles in an array. The
platform consists of an array of magnetic spin-valve
elements separated from the biological sample by
an optically transparent thin membrane, effectively
isolating the electronic or magnetic components

Video micrographs showing the rotation of a strand
of magnetic particles while trapped at the edge of
asingle “on” state spin-valve element (highlighted
by the white ellipses). The magnetic beads are 2.8
micrometers in diameter.



which is the size of a grain of rice.

m Force Standard Reference Material for
AFM Calibrations — We are designing a piezo-
resistive cantilever force sensor that can serve as
a force and/or stiffness SRM. The beam thickness
in the gauge area was reduced to produce high
sensitivity. The trade-off-for this sensitivity is a
more complex artifact with the need to maintain
additional critical dimensions. The numbered fidu-
cial marks shown in the figure indicate points along
the cantilever’s length where a calibrated stiffness
will be determined. The functional dependence of
stiffness on test location is more complicated in
this design, but can be modeled assuming the gauge
area acts as a cantilever hinge and the remainder of
the beam is a rigid lever arm. The exact functional
relationship will be examined using the electronic
force balance in the Manufacturing Engineering
Laboratory. As with the previously described stiff-

ness SRMs, the goal is to settle on a fabrication
strategy that yields a high degree of uniformity
within a wafer. We hope to use resonance fre-
quency, this time conveniently measured from the
piezoresistor, with a bridge as a process monitor
to check for mechanical uniformity within a wafer
run. This sensor is currently in prototype produc-
tion and testing results are not yet available.

Awarp

U.S. Department of Commerce Silver Medal for
the design, construction, and testing of the first
operational chip-scale atomic clock and chip-
scale magnetometer based on atomic transitions,
2005 (John Moreland, Li-Anne Liew, EEEL; John
Kitching, Peter Schwindt, Hugh Robinson, and Leo
Hollberg, Physics Laboratory).

REcENT PuBLICATIONS

S. Knappe, P. Schwindt, V. Gerginov, V. Shah, A. Brannon,
B, Linseth, L. Liew, H. Robinson, J. Moreland, Z. Popovic,
L. Hollberg, and J. Kitching, “Chip-Scale Atomic Devices,”
Proc. International Symposium on Quantum Electronics, 2006
(in press).

S. Knappe, P. D. D. Schwindt, V. Gerginov, V. Shah, L. Liew,
J. Moreland, H. G. Robinson, L. Hollberg, and J. Kitching,
“Microfabricated Atomic Clocks and Magnetometers,” Proc.
IEEE/LEOS Optical MEMS Conf, Big Sky, MT, August 2006
(in press).

E, Mirowski, J. Moreland, 8. B, Russek, and M. Donahue, “Ma-
nipulation of Magnetic Particles by Pattemed Arrays of Mag-
netic Spin-Valve Traps,” J. Magn. Magn. Mater. (in press).

S. Lee, T. M. Wallis, J. Moreland, P. Kabos, and Y. C. Lee,
“Asymmetric Dielectric Trilayer Cantilever Probe for Calori-
metric High Frequency Field Imaging,” IEEE J. Microelectro-
mech, Syst. (in press).

Y.-J. Wang, M. Eardley, S. Knappe, J. Moreland, L, Hollberg,
and J. Kitching, “Magnetic Resonance in an Atomic Vapor Ex-
cited by a Mechanical Resonator,” Phys, Rev. Lett. 97, 227602
(December 2006).

L. Yuan, L. Gao, R, Sabirianov, S, Liou, M. Chabot, D. Min, J.
Moreland, and B. S. Han, “Microcantilever Torque Magnetom-
etry Study of Patterned Magnetic Films,” IEEE Trans. Magn.
42, 3234-3236 (October 2006).

Prototype piezoresistive cantilever SRM for calibrat-
ing AFMs. The cantilever is 500 micrometers long.

T. M. Wallis, J. Moreland, and P. Kabos, “Binstein—de Haas
Effect in a NiFe Film Deposited on a Microcantilever,” Appl.
Phys. Lett. 89, 122502 (September 2006).

L. Liew, J. Moreland, and V. Gerginoy, “Wafer-Level Fab-
rication and Filling of Cesium-Vapor Resonance Cells for
Chip-Scale Atomic Devices,” Proc. 20th Eurosensors Conf,
Goteborg, Sweden, paper W1B-O2 (September 2006).

S. Knappe, P. D. D. Schwindt, V. Gerginoy, V. Shah, L. Liew,
J. Moreland, H. G. Robinson, L. Hollberg, and J. Kitching,
“Microfabricated Atomic Clocks and Magnetometers,” J. Optics
A: Pure and Applied Optics 8, S318-S332 (July 2006).



J. R. Pratt, J. A. Kramar, G. Shaw, R. Gates, P. Rice, and
J. Moreland, “New Reference Standards and Artifacts for
Nanoscale Property Characterization,” Tech. Proc. 9th NSTI
Nanotechnology Conf. and Trade Show, May 2006, vol. 1, pp.
764-767 (Suly 2006).

J. Kitching, $. Knappe, P. D. D. Schwindt, Y.-J. Wang, H.
Robinson, L. Hollberg, L. Liew, J. Moreland, A. Brannon, J.
Breitbarth, B. Lindseth, Z. Popovic, V. Shah, V. Gerginov, and
M. Eardley, “Chip-Scale Atomic Devices,” Proc. Solid State
Sensors, Actuators and Microsystems Workshop, Hilton Head
Island, SC, pp. 108-113 (June 2006).

S. Lee, Y. C. Lee, T. M. Wallis, J. Moreland, and P. Kabos,
“Near-Field Imaging of High-Frequency Magnetic Fields with
Calorimetric Cantilever Probes,” J. Appl. Phys. 99, 08306
(April 2006).

J. Moreland, J. Kitching, P, D. D. Schwindt, 8. Knappe, L. Liew,
V. Shab, V. Gerginoy, Y. Wang, and L. W. Hollberg, “Chip Scale
‘Atomic Magnetometers,” Military Sensing Symposia Specialty
Group on Battlefield Acoustic and Seismic Sensing, Magnetic
and Electric Field Sensors, August 2005, Laurel, MD, pp. 1-10
(April 2006).

J. Kitching, S. Knappe, L. Liew, J. Moreland, H. G. Robinson,
P.D. D. Schwindt, V. Shah, V. Gerginoy, and L. W. Hollberg,
“Chip-Scale Atomic Frequency References: Fabrication and
Performance,” Proc. 19th European Frequency and Time Forum,
Besancon, France, pp. 575-580 (December 2005).

M. Chabot, J. Moreland, L. Gao, S. H. Liou, and C. W. Miller,
“Novel Fabrication of Micromechanical Oscillators with Na-
noscale Sensitivity at Room Temperature,” J. Microelectromech.
Syst. 14, 1118 (October 2005).

J. Kitching, S. Knappe, L.-A. Liew, P. D. D. Schwindt, V.
Gerginoy, V. Shah, J. Moreland, A. Brannon, J. Breitbarth,
Z. Popovic, and L. Hollberg, “Chip-Scale Atomic Frequency
References,” Proc. Institute of Navigation (ION-GNSS), Long
Beach, CA, pp. 1662-1669 (September 2005).

V. Gerginoy, S. Knappe, P. D. D. Schwindt, V. Shah, L. Liew, J.
Moreland, H. G. Robinson, L. Hollberg, J. Kitching, A. Brannon,
J. Breitbarth, and Z. Popovic, “Component-Level Demonstra-
tion of a Microfabricated Atomic Frequency Reference,” Proc.
IEEE International Frequency Control Symposium Vancouver,
BC, pp. 758-766 (August 2005).

J. Kitching, 8. Knappe, L. Liew, P. D. D. Schwindt, V. Shab,
J. Moreland, and L. W. Hollberg, “Microfabricated Atomic
Clocks,” 18th International Conference on Micro-Electro-
Mechanical Systems, January 2005, Miami, FL, pp. 1-7 (July
2005).

J. Kitching, S. Knappe, L. Liew, J. Moreland, P, D.D. Schwindt,
V. Shah, V. Gerginov, and L. Hollberg, “Microfabricated
‘Atomic Frequency References,” Metrologia 42, $100-S104
(June 2005).

E. Mirowski, J. Moreland, A. Zhang, 8. E. Russek, and M. J.
Donahue, “Manipulation and Sorting of Magnetic Particles by
a Magnetic Force Microscope on a Microfluidic Magnetic Trap
Platform,” Appl. Phys. Lett. 86, 243901 (June 2005).

D. Min and J. Moreland, “Quantitative Measurement of
Magnetic Moments with a Torsional Resonator: Proposal for
an Ultralow Moment Reference Material,” J. Appl. Phys. 97,
10R504 (May 2005).

S. Knappe, P. D. D. Schwindt, V. Shah, L. W. Hollberg, J.
Kitching, L. Liew, and J. Moreland, “A Chipscale Atomic Clock
Based on 87Rb with Improved Frequency Stability,” Optics
Express 13, 1249-1253 (February 2005).

T.M. Wallis, J. Moreland, B. Riddle, and P. Kabos, “Microwave
Power Imaging with Ferromagnetic Calorimeter Probes on
Bimaterial Cantilevers,” J. Magn. Magn. Mater. 286, 320-323
(February 2005).

D. Min, A. McCallum, S. E. Russek, and J. Moreland, “Mi-
cromechanical Torque Magnetometer with Sub-Monolayer
Sensitivity,” J. Magn. Magn, Mater. 286, 329-335 (February
2005).

P.D.D. Schwindt, S. Knappe, V. Shah, L. W. Hollberg, J. Kitch-
ing, J. Moreland, and L. Liew, “Chipscale Atomic Magnetom-
eter,” Appl. Phys. Lett. 85, 6409-6411 (December 2004).

S. Knappe, V. Shah, P, D. D. Schwindt, L. Hollberg, J. Kitch-
ing, L.-A. Liew, and J. Moreland, “A Microfabricated Atomic
Clock,” ppl. Phys. Lett. 85, 1460-1462 (August 2004).

L. Gao, D. Q. Feng, L. Yuan, T. Yokota, R. Sabirianov, S. H.
Liou, M. D. Chabot, D. Porpora, and J. Moreland, “A Study of
Magnetic Interactions of Ni80Fe20 Arrays Using Ultrasensitive
Microcantilever Torque Magnetometry,” J. Appl. Phys. 95,
7010-7012 (June 2004).

L.-A. Liew, S. Knappe, J. Moreland, H. Robinson, L. Hollberg,
and J. Kitching, “Microfabricated Alkali Atom Vapor Cells,”
Appl. Phys. Lett. 84, 2694-2696 (April 2004).

E. Mirowski, J. Moreland, S. E. Russek, and M. J. Donahue,
“Tntegrated Microfluidic Isolation Platform for Magnetic Par-
ticle Manipulation in Biological Systems,” Appl. Phys. Lett. 84,
1786-1788 (March 2004).



Technical Contact:
Lorant Muth

Staff-Years (FY 2006):
1.0 professional

AANTENNAS AND ANTENNA SysTEMms:
MetRoLocy For Rapar Cross SEcTION SYSTEMS

Goats

The Metrology for Radar Cross Section Systems
Project assists the U.S. Department of Defense
(DOD) and industrial radar cross section (RCS)
measurement ranges to create and implement a Na-
tional DOD Quality Assurance Program to ensure
high-quality RCS calibrations and measurements
with stated uncertainties.

Customer NEEDS

RCS measurements on complex targets, such as
aircraft, ships, and missiles, are made at different
types of RCS measurement ranges, including com-
pact ranges (indoor static), and outdoor static or
dynamic facilities. Measurements taken at various
ranges on the same targets must agree with each
other within stated uncertainties to increase con-
fidence in RCS measurements industry-wide. Al-
though the sources of uncertainty are well known,
a comprehensive determination of the magnitudes
of uncertainties in RCS calibrations require well
formulated procedures that measurement ranges
can use to determine their uncertainties. Customer
needs include:

Calibration Artifacts — RCS users need im-
proved calibration artifacts that are dimensionally
traceable and calculable and exhibit wide dynamic
range.

Calibration Procedures — Calibration proce-
dures and data analysis techniques are needed to
minimize range uncertainties at both government
and industrial RCS ranges. The implementation
of improved procedures and the determination of
range uncertainties at every RCS measurement
range are essential if the U.S. RCS industry is to
maintain its world leadership.

TECHNICAL STRATEGY

The complex measurement systems and measure-
ment practices at RCS ranges should be docu-
mented uniformly throughout the industry so that
meaningful comparison of capabilities and impor-
tant range-to-range differences are recognized. The
framework of a RCS Range Book, in the context of
aDOD RCS Self-Certification Program, is used to
ensure community-wide compliance.

We provide RCS Range Book reviews for the DOD
and industrial RCS ranges. These in-depth reviews

provide guidance to the RCS community as they
pursue their industry-wide certification program.
The uncertainty analyses pursued by the U.S. RCS
ranges are based on the pioneering NIST work in
this area.

We have continued to work closely with selected
RCS measurement ranges to develop and standard-
ize procedures to determine RCS calibration and
measurement uncertainty for both monostatic and
bistatic RCS measurements. Fully polarimetric
calibration procedures are also being studied.

To support these research activities we have rec-
ommended an expanded set of RCS calibration
cylinders to calibrate the system at various signal
levels of interest using a single artifact. To support
polarimetric calibration research, we recommended
a set of calibration dihedrals that can be used to
determine system parameters needed to analyze
polarimetric calibration data.

We seek to fully assess the technical merit and
deficiencies of existing calibration and measure-
ment procedures, data-analysis techniques, and
uncertainty analysis. We plan to publish recom-
mendations for improvements in these areas, We
plan to further explore known problems in areas
such as dynamic sphere calibration, polarimetric
calibration, and bistatic RCS calibration.

The annual RCS Certification Meeting held at
NIST-Boulder provides a forum for the RCS com-
munity to discuss procedural and technical issues
on an ongoing basis.

ACCOMPLISHMENTS

= Cylinder Calibration Set — The RCS com-
munity has adopted a basic cylinder calibration
set to test the calibration integrity of monostatic
RCS systems. Computed radar cross sections for
the cylinder set have been obtained. These four
cylinders have been measured at a number of
government and industrial measurement ranges,
with agreement with the theoretical RCS of better
than 0.5 decibels. These comparisons demonstrate
good repeatability; however, we need more robust
independent measurement procedures to determine
the measurement uncertainties.

= Dihedral Calibration Set— We designed and
manufactured a set of calibration cylinders with di-
hedral cutouts that can be used to calibrate an RCS

lEngineering Laboratory]



MetrRoLocy For Macnetic RESONANCE IMAGING ARTIFACTS AND STABILITY
L. F. Goodrich and S. E. Russek

Research focuses on developing metrology for magnetic resonance imaging (MRI) system stability and
intercomparability and image distortion. This is part of a new NIST effort to assist the medical imag-
ing community in developing more quantitative images that are traceable to the International System
of Units (SI). We intend to conduct studies to assess MRI system stability and intercomparability using
NIST-generated artifacts and assess methods to identify sources of instability in MRI coils systems:
superconducting solenoid, shim coils, gradient coils, and RF coils. We plan to develop metrology to
analyze magnetic imaging distortions as a result of implants such as stents and coils. This will involve
evaluating magnetic properties of MRI system components and implants that could lead to image distor-
tion. Measurements will be made using a7 tesla SQUID magnetometer, a 7-tesla/300-megahertz nuclear
magnetic resonance system, and other superconducting high-magnetic field systems at NIST-Boulder.
All of these studies will also involve measurements conducted in commercial MRI systems at local
hospitals and at the National Institutes of Health (NIH). This opportunity is appropriate for physicists,
chemical-physicists, or engineers interested in medical physics or medical engineering.

Superconpuctor MeAsuREMENTS
L. F. Goodrich

We develop and evaluate measurement techniques to determine the critical parameters and matrix
properties of superconductors. Capabilities include variable-temperature critical-current measurement,
low-noise current supplies up to 3000 amperes, high-field magnets up to 18 teslas, and voltage sensitivity
to 1 nanovolt. We study conventional superconductors (NbTi and. Nb,Sn) and the newer high-transition-
temperature materials. We conduct fundamental studies of the superconducting-normal transitions and
the parameters that affect their accurate determination, such as current transfer, strain, or inhomogeneities
in materials and fields. We develop theoretical models to interpret current redistribution and component
interactions in composite superconductors.

CELLULAR IMAGING AND MANIPULATION WITH SUPERPARAMAGNETIG PARTICLES
(Joint NIH/NIST)
J. Moreland

We are currently developing technologies for characterizing and manipulating magnetic particles for
in-vivo magnetic resonance imaging (MRI) and cell manipulation. Applications include tags and contrast
agents for imaging single cells in organs as well as very high resolution imaging of the organelles in a
single cell. In addition, we are developing ways of using magnetic particles to move to predetermined
locations or to switch cell functionality. Understanding the nanoscopic physical properties of the particles
is critical for exploring and tailoring them to specific applications. The main areas of interest include:
(1) characterizing the size, shape, biofunctionality, and nanoscopic field patterns of superparamagnetic
particles with the objective of developing methods for narrowing the statistical distributions of each
of these properties; (2) understanding natural biological magnetic systems and their physicochemical
processes; and (3) developing magnetic force manipulation techniques for moving and switching cell
functionality and for injecting cells with superparamagnetic particles.

Cnip-Scace Macnetic Resonance Imacinc Microscore
J. Moreland

Conventional magnetic resonance imaging (MRI) systems are limited in resolution because of the noise
of inductive detectors, which limits sensitivity, as well as difficulties generating field gradients sufficient
for narrow sample slice discrimination. By using micromechanical cantilever oscillators as magnetic
sensors and by reducing the dimensions of the gradient coils, significant improvements in sensitivity
and resolution can be made. In particular, we have recently demonstrated several micromechanical
magnetometers including a magnetic resonance force microscope, a torque magnetometer, and a mi-
cromechanical calorimeter. These magnetometers operate on the principle of modulating the magnetic

CLOW



INTRODUCTION TO TECHNICAL PROGRAMS

The division carries out a broad range of technical programs focused on the precise realization
and measurement of physical quantities throughout the radio spectrum. Key directions include:
(a) the development of reference standard artifacts, services and processes with which industry
can maintain internationally recognized measurement traceability; (b) the advancement of
technology through the development of new measurement techniques that are theoretically and
experimentally sound as well as relevant and practical; (c) the assessment of total measurement
uncertainties; and (d) the provision of expert technical support for national and international
standards activities. We strive to perform leading-edge, high-quality research in metrology that
is responsive to national needs. Division programs cover the following technical areas:

Microwave MeasuremeNT SERVICES

Through the microwave measurement services, we establish, maintain, and disseminate the
national standards for RF and microwave quantities. This provides the U.S scientific and in-
dustrial base with access to a measurement system that is readily available, reliable, accurate,
reproducible, and internationally consistent. We provide a broad range of state-of-the-art RF
and microwave calibration services, which include scattering parameters, attenuation, power,
thermal noise, and waveform.

Micro/Nano ELecTRoNIcs

This program seeks to develop new metrology tools for next-generation electromagnetic ap-
plications in high-speed telecommunications, microelectronics, magnetic data storage, com-
puting, and biomedical systems. These new tools are focused on higher operating frequencies,
wider bandwidths, increased dynamic range, smaller length scale, and more complex materials,

. devices, and systems.

ELecTROMAGNETIC PROPERTIES OF MATERIALS

The electromagnetic properties of materials program develops theory and methods for measur-
ing the complex permittivities and permeabilities of materials at frequencies from RF through
terahertz. Materials of interest include electronic substrates, thin films, liquids, biological
specimens, and engineered materials. Characterization is performed of both bulk and micro-
and nanoscale properties.

ANTENNAS AND ANTENNA SysTEMS

The antennas and antenna systems program develops theory and techniques for measuring the
gain, pattern, and polarization of advanced antennas; for measuring the gain and noise of large
antenna systems; and for analyzing radar cross-section measurement systems.

ELECTROMAGNETIC COMPATIBILITY

The electromagnetic compatibility program develops theory and methods for measuring electro-
magnetic field quantities and for characterizing the emissions and susceptibilities of electronic
devices and systems, in both the frequency and time domains.

SUPERCONDUCTOR CHARACTERIZATION AND STANDARDS

The program in superconductor characterization and standards develops measurement methods
for the electric, magnetic, and mechanical properties of high-temperature and low-temperature
superconductor wires and tapes for electric power applications.



WELcomeE

The Electromagnetics Division is a critical national resource for a wide range of customers. U.S.
industry is the primary customer both for the division’s measurement services and for technical
support of test and measurement methodology necessary for research, product development,
manufacturing, and international trade. The division represents the U.S. in international mea-
surement comparisons and standards development related to radio-frequency and microwave
technology, electromagnetic fields, and superconductors. The division also provides measure-
ment services and expert technical support to other agencies of the federal government in sup-
Port of its programs in domestic and international commerce, national defense, transportation
and communication, public health and safety, and law enforcement.

The division is organized into three groups. The groups’ projects are led by senior technical
staff with the assistance of physicists, engineers, technicians, and research associates, as well
as graduate and undergraduate students.

The Radio-Frequency Electronics Group conducts theoretical and experimental research to
develop basic metrology, special measurement techniques, and measurement standards necessary
for advancing both conventional and microcircuit guided-wave technologies; for characterizing
active and passive devices and networks; and for providing measurement services for scattering
parameters, power, waveform, noise, material properties, and other basic quantities.

The Radio-Frequency Fields Group conducts theoretical and experimental research necessary
for the accurate measurement of free-space electromagnetic field quantities; for the charac-
terization of antennas, probes and antenna systems; for the development of effective methods
for electromagnetic compatibility assessment; for the measurement of radar cross section and
radiated noise; and for providing measurement services for essential parameters.

The Magnetics Group develops measurement technology for industries broadly concerned
with magnetic information storage, biomagnetic imaging, and superconductor power, span-
ning the range from practical engineering to theoretical modeling. The group disseminates the
results of its research through publications in refereed journals, presentations at conferences
and workshops, and participation in standards organizations.

We hope that this collection of information will help you in understanding the work of the
division and in making use of the technical capabilities and services that we provide for indus-
try, government, and academia. We invite you to visit our Web site, http:/Avww.boulder.nist.
gov/div8 18. This site will provide you with more information on our projects and measurement
related software, and reprints of our publications. Thank you for your interest in the Electro-
magnetics Division.

Michael Kelley, Chief, Electromagnetics Division
Ron Ginley, Acting Leader, Radio-Frequency Electronics Group
Perry Wilson, Leader, Radio-Frequency Fields Group

Ron Goldfarb, Leader, Magnetics Group



We developed a coaxial waveform measurement
service that is traceable to our electro-optic sam-
pling system. It includes point-by-point uncertain-
ties and correction for mismatches, and is traceable
to 110 gigahertz. We demonstrated the ability to
generate and accurately characterize pulses on-
wafer with the NIST electro-optic sampling system.
up to 200 gigahertz, important for characterizing
AO gigabit and higher communications systems. We
developed new measurements for characterizing
microwave mixers and modulated signal sources.
We also developed a new 110 gigahertz, 1.0 mil-
limeter coaxial scattering-parameter calibration and
covariance-based uncertainty analysis.

m_ Thermal Noise Characterization at Tera-
hertz Frequencies — Applications of electromag-
netic measurements at terahertz frequencies are
poised for explosive growth, but lack of fundamen-
tal standards is a serious impediment. Traceability
to NIST noise standards at terahertz frequencies
would allow comparison of different measurements
and meaningful comparison of performance of
components and systems.

For characterization of cryogenic amplifiers, we
developed a method for accurate noise figure
measurements. We measured effective input noise
temperatures in the 1 to 12 gigahertz range, with
results as low as 2.3 kelvins with a standard uncer-
tainty of 0.3 kelvin, corresponding to a noise figure
of 0.034 decibels + 0.004 decibels. We developed
and demonstrated a terahertz receiver with a quasi-
optical adapter for coupling incident radiation into a
receiver. The receiver is based on heterodyne detec-
tion with a hot-electron-bolometer (HEB) mixer.
To house the receiver portion of the radiometer, we
purchased and instrumented a cryocooler.

m Passive Spectral Terahertz Imaging —
Much interest exists in applications for imaging and
spectroscopy at terahertz frequencies. We devel-
oped a two-dimensional scanning passive terahertz
imaging system based on a phonon-cooled quasi-
optically coupled HEB mixer that is integrated with
an InP monolithic microwave integrated circuit
(MMIC) intermediate frequency (IF) low-noise
amplifier. We demonstrated the ability of a scan-
ning passive terahertz imaging system to obtain
full two-dimensional images of various objects by
scanning the target with a flat mirror mounted ona
computer-controlled elevation/azimuth translator.
The overall sensitivity, defined in terms of noise
equivalent delta temperature (NEAT), is better
than 0.5 kelvin.

m Metrology for Wireless Systems — We are
developing test methods to characterize signal
degradation, including attenuation and phase
distortion, in complex environments including
large buildings and basements. In particular, we
are focusing on development of wideband mea-
surement methods in the new 4.9 gigahertz public
safety radio band for transmission of voice, data,
images, and video.

To improve measurements of wideband, modu-
lated signals, we developed a method to extend
the measurement bandwidth of narrowband vec-
tor receivers. We developed impedance mismatch
correction techniques for vector signal generators
in their large-signal operating state. In one recent
application, we investigated the viability of us-
ing RF modulated-signal measurements order to
identify nodes in a wireless local-area network. We
performed measurements of wideband, modulated
signals in typical first-responder environments.

10cm

Photograph (left) and 0.850 terahertz image (right) of two objects at room temperature suspended over an
absorber immersed in liquid nitrogen. The terahertz image covers a temperature range of 200 kelvins.



ELecTROMAGNETICS Division STAFF

Michael Kelley, Division Chief
Dennis Friday, Chief Scientist
Cindy Kotary, Secretary
Linda Derr, Administrative Officer
Kate Remley, Technical Liaison...
Gerome Reeve, Research Associate........
Claude Weil, Research Associate
Lindsey Vaughan, Student.

(303) 497-3131
vane -3133

ou 73132
4202
3652
3557
305

Rapio-Frequency Etectronics Group

Ron Ginley, Acting Group Leader
Susie Rivera, Secretary

Microwave Measurement SERVICES
Ron Ginley, Project Leader.
Robert Billinger ..............
Tom Crowley
Puanani DeLara.
Denis LeGolvan
Ann Monke...
Juanita Morga:
James Randa.
David Walker
Dylan Williams

Micro/Nano ELectRonics

Mike Janezic, Project Leader...........+ -3656
Jim Baker-Jarvis
Rob Billinger.
Jim Booth.
Pavel Kabos

(303) 497-3634

Micro/Nano ELEcTRONIcS (CONTINUED)

Amanda Cox, Research Associate ......... ~-4653
Eyal Gerecht, Research Associate.........- -4199
Dazhen Gu, Research Associate . 3939
Atif Imtiaz, Research Associate. 4938
Arek Lewandowski,

Research AssOciate....c..scsseeeeeenes -4665
Mu-Hong (Martin) Lin,

Research Associate. -4369

Hans Nembach, Research Associat
Mitch Wallis, Research Associat
Nathan Orloff, Graduate Student
ELECTROMAGNETIC PROPERTIES OF MATERIALS
--5490
.-7900

Jim Baker-Jarvis, Project Leader

Pavel Kabos
Bill Riddle...

Robin Powers, Student

Nita Morgan ‘Atif Imtiaz, Research Associate............. 49358
James Randa.. Mu-Hong (Martin) Lin,

| Kate Remley. Research Associate.

H Bill Riddle.. Jordi Mateu, Research Associate
Dave Walker.. Mitch Wallis, Research Associate........... ~5089
Dylan Williams



Division Publication Editor:
Publication Coordinator:
Printing Coordinator:

Document Production:

Ron Goldfarb
Erik M. Secula
Tise Putman

Technology & Management Services, Inc.
Gaithersburg, Maryland



also to examine the suitability of such nanoscale devices for microwave electronics. We are specifically
pursuing research in: (1) increasing output power from nanoscale oscillators through materials engineering
and incorporating tunnel junctions into the device structures, (2) understanding the interactions between
mutually synchronized nanoscale oscillators in order to develop device arrays, (3) characterizing and
understanding the thermal contributions to both oscillator linewidths and the current induced switching
distributions in patterned elements, (4) understanding the interactions between individual magnetic nano-
structures and AC fields and AC currents, and (5) investigating the current-induced switching properties
of patterned magnetic nanostructures for magnetic random-access memory (MRAM) applications.

Macnetic Sensors, SPINTRONIC MATERIALS, AND NANOMAGNETIC IMAGING
S. E. Russek and W. H. Rippard

Spin-dependent transport is a widely used, yet poorly understood, phenomenon. Giant magnetoresistive
(GMR) devices and magnetic tunnel junctions (MTJ) are being developed for use in magnetic record-
ing heads, magnetoresistive random access memories (MRAM), and magnetic sensors for industrial
and biomedical applications. The goal of this research opportunity is to develop a better fundamental
understanding of spin-dependent transport in magnetic metals, normal metals, conducting oxides, and
semiconductors. Research areas include understanding spin polarization in exotic materials, examining
the effects of interfaces, and looking at the nanomagnetic structure that gives rise to noise and device-
to-device variation. This research involves fabrication of novel magnetic devices such as GMR, MTJ,
and spin-transfer devices using a state-of-the-art, eight-source, ultrahigh vacuum deposition system and
a combination of optical, electron-beam, and scanned-probe lithography. Electrical measurements, over
a wide range of temperature, field, and frequency, will be used to characterize spin-dependent transport
properties with a particular emphasis on high-frequency and noise properties of the devices. Lorentz and
magnetic force microscopy will be used to characterize nanoscale magnetic structures. New types of
dynamical nanoscale imaging, such as those based on ballistic electron magnetic microscopy (BEMM),
will be developed.

Biomacnetic IMAGING
S. E. Russek and P. Kabos

This research will focus on developing advanced magnetic resonance imaging (MRI). Nanomagnetic
contrast agents will be fabricated and characterized. The nanomagnets to be investigated include mo-
lecular nanomagnets, such as Fe,, and nanoparticles formed by novel thin-film self assembly techniques.
The nanomagnets will be characterized using SQUID magnetometry and electron spin resonance (ESR)
at fields up to 7 teslas and frequencies up to 140 gigahertz. The affect of the nanomagnets on nuclear
magnetic resonance (NMR) properties of protons in biological solutions will be studied. Systems that
can simultaneously measure NMR, ESR, and nanomagnet magnetization will be developed. A detailed
understanding of how the nanomagnet properties, such as anisotropies and fluctuations, affect proton
relaxation in biological solutions will be developed. MRI imaging of potential nanomagnetic contrast
agents will be done on commercial MRI systems at local hospitals. Materials with different relaxation
times will be investigated for use in MRI standards and phantoms.

HicH-FRequency CHARACTERIZATION OF NoveL THIN-FiLm MATERIALS
S. E. Russek, J. R. Baker-Jarvis, and P. Kabos

The goal of this project is to fabricate novel nano-engineered thin-film materials and measure their
electromagnetic properties in the 1 to 100 gigahertz regime. The materials include nanostructured ma-
terials, composite ferromagnetic-ferroelectric materials, “left-handed” materials, and frequency-tunable
materials. The materials can be fabricated with an ultrahigh vacuum, eight-source sputtering system, a
laser ablation system, and optical and electron-beam lithography systems. The dielectric and magnetic
properties can be engineered by patterning arrays of elements on two different length scales. Patterning
ona scale comparable to the excitation wavelength — about 1 millimeter — will allow the development
of artificial crystals (photonic band gap materials) in the microwave regime. Patterning on a scale much



APPENDIX C:
PREFIXES FOR THE INTERNATIONAL SYSTEM OF

Units (SI)
Multiplication Prefix Symbol Multiplication Prefix Symbol
Factor Factor
10% yotta Y 107 deci d
10! zetta Z 10? centi ©
108 exa E 10° milli m
105 peta P 10° micro vy
10? tera T 10° nano n
10° giga G 10"? pico p
10° mega M 1075 femto f
10 kilo k 1078 atto a
10? hecto h 107 zepto Zz
10! deka da 1074 yocto y



m Phase Noise — In collaboration with the
Physics Laboratory, a ceramic 10 gigahertz air
filled cavity was designed and constructed for use
in the X-band phase noise measurement system.
Preliminary measurements have indicated an im-
provement of 10 decibels for close-in phase noise.
Also, design work and construction of a 40 giga-
hertz metallic cavity was successfully completed
and incorporated into a basic discriminator circuit
at 40 gigahertz, Ceramic versions of this cavity are
now being constructed, with expected improvement
in phase noise equivalent to the results obtained
with the 10 gigahertz cavity.

m Standards and Comparisons — In response
to documented industry needs, a new standard for
the IPC High-Frequency Task Group (D-24) has
been completed and related software has been
transferred to industry. In order to test our calcu-
Jated uncertainties, we contributed specimens for
the EUROMET International Intercomparison.

=~ Measurements on Fluids — We have further
developed a switched measurement system that
allows for nearly simultaneous measurements of
fiuid-loaded devices using a DC meter, an LCR
meter, an RF network analyzer, and a microwave
vector network analyzer. We designed four-ter-
minal measurement devices to explore the role
of polarization impedances in the low-frequency
measurements of conducting fluids. We further
developed our modeling capabilities in order to
extract permittivity values from our measure-
ments. We have applied our measurement system
to an increasingly broad range of fluid systems at
different temperatures, including de-ionized water
(at temperatures of 20, 37, and 50 degrees Celsius),
and methanol, polystyrene beads, and NaCl buffer
solutions (at 20-degrees Celsius).

REcENT PUBLICATIONS

J. C. Booth, J. Mateu, M. D. Janezic, J. Baker-Jarvis, and J.
Beall, “Broadband Permittivity Measurements of Liquid and
Biological Samples Using Microfluidic Channels,” Proc. IEEE
MTT-S Int. Microwave Symp., San Francisco, CA, June 2006,
paper TH3E-4 (in press).

J. R. Baker-Jarvis, “Time-Dependent Entropy Evolution in
Microscopic and Macroscopic Electromagnetic Relaxation,”
Phys. Rev. E72, 066613 (December 2005).

B. Riddle and C. Nelson, “Impedance Control for Critically
Coupled Cavities,” Proc. 2005 Joint IEEE Int. Freq. Control
Symp., Vancouver, BC, pp. 488-493 (August 2005).

R.G. Geyer, B. Riddle, J. Krupka, L. A. Boatner, “Microwave
Dielectric Properties of Single-Crystal Quantum Paraelectrics
KTaO, and SrTiO, at Cryogenic Temperatures”, J. Appl. Phys.
97, 104111 (May 2005).

JR. Baker-Jarvis, M. D. Janezic, B. F. Riddle, R. T. Johnk, C.
L. Holloway, R. G, Geyer, and C. A. Grosvenor, “Measuring
the Permittivity and Permeability of Lossy Materials: Solids,
Liquids, Metals, and Negative-Index Materials,” NIST Techni-
cal Note 1536 (February 2005).

R. G. Geyer, J. Baker-Jarvis, and J. Krupka “Variable-Tem-
perature Microwave Dielectric Properties of Single-Crystal
Fluorides,” Ceramic Transactions 167, 51-55 (2005).

J. Baker-Jarvis, P. Kabos, and C. L. Holloway, “Nonequilibrium
Electromagnetics: Local and Macroscopic Fields and Con-
stitutive Relationships,” Phys Rev E 70, 036615 (September
2004).

M.D. Janezic, E. F. Kuester, and J. Baker-Jarvis, “Broadband
Complex Permittivity Measurements of Dielectric Substrates
using a Split-Cylinder Resonator,” Proc. IEEE MTT-S Int. Mi-
crowave Symp., Fort Worth, TX, pp.1817-1820 (June 2004).

M. D. Janezic and J. Baker-Jarvis, “Relative Permeability
Measurements for Metal-Detector Research,” NIST Technical
Note 1532 (2004).

M.D. Janezic, R. F. Kaiser, J. Baker-Jarvis, and G. Free, “DC
Conductivity Measurements of Metals,” NIST Technical Note
1531 (2004).

M.D. Janezic, “Dielectric Measurement Methods at Millimeter-
Wave Frequencies,” Proc. IMAPS Conf. Ceramic Interconnect
‘Technology, Denver, CO, pp. 221-225 (2004).

J. Baker-Jarvis, M. D. Janezic, and J. Krupka, “Broadband Di-
electric Measurement of Liquids”, Proc. IEEE Conf. Electrical
Insulation and Dielectri¢ Phenomena (CEIDP), Boulder, CO,
pp. 17-20 (October 2004).

C.A. Grosvenor, R. Johnk, D. Novotny, S. Canales, J. Baker-
Jarvis, M. Janezic, J. Drewniak, M. Koledintseva, J. Zhang, and
P. Rawa, “Electrical Material Property Measurements Using a
Free-Field, Ultra-Wideband System,” Proc. IEEE Conf. Elec-
trical Insulation and Dielectric Phenomena (CEIDP), Boulder,
CO, pp. 174-177 (October 2004).

R-G-Geyer, JB: inka, “Dielectric Char-

|
|

J. Baker-Jarvis, M. D. Janezic, D. Love, T, M. Wallis, CL. Hol-
loway, and P. Kabos, “Phase Velocity in Resonant Structures,”
IEEE Trans. Magn. 42, 3344-3346 (October 2006).

J. Baker-Jarvis, M. D. Janezic, and J. Krupka, “Measurements
of Coaxial Dielectric Samples Employing Both Transmission/
Reflection and Resonant Techniques to Enhance Air-Gap Cor-
rections,” Proc. 16th Int. Conf. Microwaves, Radar and Wireless
Commun. (MIKON), Krakow, Poland (May 2006).

aker-Jarvis, and LKny
acterization of Single-Crystal LiF, CaF,, MgF,, BaF,, and
StF, at Microwave Frequencies,” Proc. IEEE Conf. Electrical
Insulation and Dielectric Phenomena (CEIDP), Boulder, CO,
pp. 493-497 (October 2004).

J. Krupka, K. Derzakowski, M. D. Janezic, and J. Baker-

Jarvis, “TEys Dielectric:Resonator Technique for Precise
Measurements of the Complex Permittivity of Lossy Liquids
at Frequencies Below 1 GHz,” Proc. Conf. Precision Electro-
magnetic Measurements (CPEM), London, UK, pp. 469-470
une 2004).



INUST = Etectronics and ELECTRICAL
-\ [ENGINEERING LABORATORY

National Institute of

iS Cominerce ‘ oes a oe os ; y :

“NISTIR 7371 DIVISION :

danuary 2007 | ss . ioe % te
ProGrams, ACTIVITIES, AND



Appenpbix D:
Units FoR Macnetic PROPERTIES

Symbol Quantity Conversion from Gaussian and cgs emu to SI
® magnetic flux 1 Mx > 10* Wb = 10° V's
B magnetic flux density, 1G— 104 T= 104 Wb/m?
magnetic induction
AH magnetic field strength 1 Oe > 103/(4n) A/m
m magnetic moment lerg/G=1 emu 10° Am’ = 10° J/T
M magnetization 1 erg/(G-cm?) = 1 emu/em’ > 10° A/m
4nM magnetization 1G 103/(4m) AAn
fo) mass magnetization, 1 erg/(G-g) = 1 emu/g > 1 Am’/kg
specific magnetization
j magnetic dipolemoment _1 erg/G = 1 emu > 4a x 10°? Wo-m
J magnetic polarization 1 erg/(G-em*) = 1 emu/em’ > 42 x 10*T
GK susceptibility 17> 4n
Xp mass susceptibility 1 om3/g > 4x x 10° mi/kg
Lu permeability 1 4x x 10° H/m = 4x x 107 Wb/(A-m)
BL, relative permeability wou,
w,W energy density 1 erg/om? — 107 J/m3
N,D demagnetizing factor 1 1/(4n)

Gaussian units are the same as cgs emu for magnetostatics; Mx = maxwell, G = gauss,
Oe = oersted, Wb = weber, V = volt, s = second, T = tesla, m = meter, A= ampere, J = joule,
kg = kilogram, H = henry.



the plasma. The superconductors for ITER’s large
magnet systems are all “cable-in-conduit conduc-
tors” (CICC), which provide both mechanical sup-
port for the large magnetic forces and a flow path
for the liquid helium required to cool the cable. The
superconducting magnet must be operated below
the critical current of the cable, which is a function
of magnetic field and temperature. Temperature is
an important variable, and the local temperature
of the conductor depends on the mass-flow rate
of the coolant and the distribution of the heat load
along the CICC.

We designed and constructed a new variable tem-
perature probe that allows us to make measure-
ments in our 52-millimeter bore, 16-tesla magnet.
This probe replaces one that was designed for
our 86-millimeter bore, 12-tesla magnet. Fitting
everything into the smaller bore was difficult, but
the new probe performed as expected and allows
us to make measurements at the ITER design field
of 13 teslas. We made measurements up to 765
amperes with a Nb,Sn sample in flowing helium
gas. Measurements were made at temperatures
from 4 to 17 kelvins and magnetic fields from 0
to 14 teslas. Some measurements were made at 15
and 16 teslas for temperatures from 4 to 5 kelvins;
however, these magnetic fields can be generated
only when a sample is measured in liquid helium.
The results of our unique variable-temperature
measurements provide a comprehensive charac-
terization and form a basis for evaluating CICC
and magnet performance. We used these data to

es
ae

PEST THAP HK oE + HS

20

Critical current versus temperature at various mag-
netic fields for a Nb;Sn wire. These curves show the
current carrying limits for various combinations of
temperature and magnetic field.

1000

E (Vim)

0

15.
Tw

Electric field versus temperature at currents from 66
to 84 amperes in steps of 1.5 amperes for a Nb;Sn
wire. These are typical curves for the determination of
temperature margin.

generate curves of electric field versus temperature
at constant current and magnetic field. In turn, these
give a direct indication of the temperature safety
margin of the conductor.

a International Standards on Superconduc-
tivity — Many of the 14 published IEC/TC 90
standards on superconductivity contain “precision”
and “accuracy” statements rather than currently
accepted statements of “uncertainty.” NIST has ad-
vocated that TC 90 adopt a more modern approach
to uncertainty. In collaboration with the Informa-
tion Technology Laboratory, we have developed a
50-page report on the possibility of changing state-
ments of “accuracy” to statements of “uncertainty”
in IEC/TC 90 measurement standards, which was
presented at TC 90 meetings in June 2006. They
included proposed change sheets for 13 of the 14
TC 90 document standards. Ultimately, all TC 90
delegates voted in favor of changing to uncertainty
statements during the maintenance cycle of exist-
ing standards and during the development of new
standards.

= Current Ripple a Source of Measurement
Errors — All high-current power supplies contain
some current ripple and spikes. New high-perfor-
mance conductors have high critical currents that
require current supplies over 1000 amperes. High-
current power supplies with the lowest level of cur-
rent ripple and spikes are often more than a factor
of ten times more expensive than conventional



TECHNICAL STRATEGY

We provide a large range of state-of-the-art micro-
wave measurements and standards. We will con-
tinue to maintain the primary national standards in
thermal noise, s-parameters, power, and waveform
metrology, and to offer measurement services that
enable customers to achieve traceability to those
standards and to verify their own measurements.

Maintaining and delivering these services is a
major task. The systems and standards for the
services are generally designed and built at NIST
and are not commercially available. There is not a
large market for primary standards and, therefore,
companies have no economic incentive to develop
them. To cover all parameters requires many differ-
ent systems and standards, The systems are aging,
need more maintenance time, and are very costly
to replace. The primary standards that support the
services are also aging. In many cases the present
standards are either nonreplaceable, or the technical
expertise to recreate them has been lost, or the parts
of the standards obtained from commercial sources
are no longer available (for example, the WR15 and
‘WR1O0 thermistor standards that have been used are
no longer made by any manufacturer).

In part, our strategy for moving the measurement
services into the future is to develop improved
methods for delivering our services. This will
include alleviating the stress on measurement
systems and standards, new methods of support-
ing our customer needs, and more interlaboratory
comparisons.

ScatTERING PARAMETERS

‘S-parameter measurements are required for accu-
rate measurements in all of the other microwave
disciplines. An example is the mismatch correction
for power measurements that is calculated from
reflection coefficients of various parts of the system
and devices. The accuracy of s-parameter measure-
ments is directly related to the calibration of the
vector network analyzer (VNA) used for the mea-
surements. The calibration method and standards
can be chosen to match the end use. It is important
to educate the users of the modern network analyz-
ers about the choices of standards and calibration
methods and to develop tools that will enable them
to make reliable, accurate measurements.

There is an increasing demand for s-parameter
measurements. This is particularly evident for
measurements above 50 gigahertz. Higher frequen-
cies and smaller waveguide and connector sizes
are starting to be used routinely. We are going to

address these needs by adding 1.85 millimeter and
1.0 millimeter connector size capabilities to our
Measurement services in the near term and look
at supporting small waveguide sizes (frequency
coverage up to at least 500 gigahertz) in the longer
term.

There is general agreement among the principal
users and makers of VNA systems that much still
remains to be understood about VNA calibrations
and measurements. This is true for both traditional
measurement areas and emerging areas, which
include electronic calibration units, multiport,
and differential measurements. We plan to take
a very active role in developing VNA calibration
and measurement theory and techniques for these
areas. We intend to pursue these VNA techniques
to higher frequency ranges, up to approximately
500 gigahertz.

Verification of VNA calibrations is very important,
and the current verification process is not sufficient.
We will try to improve the verification process
through several different methods. The Verify
and Calkit software we have developed, which
compares the contents on verification and calibra-
tion disks to measurements made based on LRL
calibrations, will be made available to the public.
Our measurement comparison kit program will
be expanded. Finally services will be developed
to support ongoing interlaboratory comparisons.
These will aid not only in system verification, but
also in proficiency testing for accreditation.

S-parameter measurement comparison kits for Type-N
7 millimeter, 3.5 millimeter, 2.92 millimeter and 2.4
millimeter coaxial connectors.

Noise

We have recently added the capability to perform
noise-parameter measurements on low-noise am-
plifiers, and we plan to develop mechanisms, such
as verification methods, to support such measure-



E

Microwave MEASUREMENT SERVICES

Goats

The goal of the Microwave Measurement
Service Project is to ensure the availability
for the U.S. scientific and industrial base of
a measurement system for radio frequency
(RF) and microwave quantities that is reliable,
accurate, reproducible, traceable to the Inter-
national System of Units (SD), and internation-
ally consistent. We do this by developing and
maintaining the U.S. national measurement
standards for RF and microwave quantities,
providing a wide range of state-of-the-art
calibration services, and developing new mea-
surement methods and verification techniques
to improve the quantitative measurement of
microwave quantities.

Setting up experimental vector network analyzer cali-
bration using 1.5 millimeter airline standard.

Customer NEEDS

The customers who use our services span a
large part of the electronics industry. They
include aeronautics and communication com-
panies, instrument manufacturers, and other

——-government-agencies-Additionally-we-make

measurements for many internal programs in
areas such as antennas, optoelectronics, and
electromagnetic properties of materials. Our
services provide the fundamental microwave
properties that customers rely on to establish
the critical factors in design and performance
of RF and microwave equipment. Our custom-
ers also establish traceability to the SI through
our measurements. Economic gains are real-

ized through improvements in accuracy. The
verification of calibrations and measurement
processes on commonly used microwave mea-
surement systems is of paramount importance
to our customers. We support this through
our measurements and the techniques that we
make available.

Microwave metrology is expanding in many
different directions. There is a constant push to
use higher frequencies. Signals are becoming
much more complex and include modulation
effects, multiport/differential signals, complex
waveforms, and other unusual signal schemes.
On-wafer measurements are in greater de-
mand. Improved means for the dissemination
of our services are also necessary. These new
requirements are dictated by the needs of
the telecommunication and computing com-
munities; 100 gigabit per second data rates
will require 400 gigahertz support as well
as modulated power, waveform analysis and
other signal scheme support. Optoelectronic
applications need scattering parameter (s-
parameter) and power measurement support
above 50 gigahertz in 1.85 millimeter con-
nectors. Molecular resonance measurements
for chemical identification will need preci-
sion measurement support in the 500 to 700
gigahertz range. Remote sensing will require
measurements of unprecedented accuracy.
New imaging systems will require support in
many different microwave parameter areas.

Technical Contacts:
Ron Ginley

Tom Crowley

Dave Walker

Staff-Years (FY 2006):
3.7 professionals
4.1 technicians

24 millimeter thin-film primary power transfer
standard.



MRI Stanparps AnD Contrast AGENT
MetroLocy

We develop new techniques to characterize nano-
magnetic materials for improved MRI contrast and
to fabricate quantitative MRI phantoms. Nano-
magnetic materials in solid, liquid, or gel phases
are studied with SQUID magnetometry, EPR, and
NMR. We have installed an NMR relaxometer
that can measure the nuclear relaxation induced in
biological systems by neighboring nanomagnets.
The relaxometer can measure over a field range
of 0.5 to 7 teslas and NMR frequency range of 20
to 300 megahertz. Traceable standards are being
developed to help monitor MRI stability and inter-
comparability and to enable quantitative MRI.

AccoMmPLISHMENTS

m Low-Frequency Noise Measurements
on Magnetic Field Sensors — Low-frequency
noise was measured in the frequency range from
0.1 hertz to 10 kilohertz on a variety of com-
mercially available magnetic sensors and custom
sensors fabricated at NIST. The types of sensors
investigated include those based on anisotropic
magnetoresistance (AMR), GMR, TMR, giant
magnetoimpedance (GMI), and fluxgate devices.
The 1/fnoise components of electronic and mag-

magnetic field sensors. Two different sensors are
currently under development: a low power sensor
(less than 100 microwatts) with a field detectivity
of 1 nanotesla per root hertz was demonstrated this
year, and a low field sensor with field detectivity
of 1 picotesla per root hertz will be demonstrated
next year. These sensors are small, low in cost,

“and compatible with complementary metal oxide
semiconductors (CMOS), and will enable many
applications for which there are currently no sen-
sor solutions.

S.

Soo
Si Hall

Ss

5.

Minimum Detectable Field (T/Hz'”)

10

2

Frequency (Hz)

Low frequency noise measured in different types of
magnetic field sensors.

= Dynamic Lorentz Imaging of Magnetic
Tunnel Junctions — In collaboration with the
Materials Science and Engineering Laboratory, we
studied disorder in MTJs using dynamic Lorentz
microscopy. Lorentz microscopy is a form of
transmission electron microscopy (TEM) that uses
the defection of electrons as they pass through a
magnetic sample to image nanoscale magnetic
structure. The advantages of Lorentz microscopy
are that it can image the interior of a complicated
device stack, it acquires data in parallel allowing
rapid image acquisition needed for dynamic imag-
ing, and it can image nanoscale structural defects
that can give rise to the magnetic disorder. Con-
siderable disorder in the free layer of the MTJ was

7——netie-origin-were-identified-by-measuring-sensor
noise and sensitivity at various applied magnetic
fields. For the GMR sensors, both electronic and
magnetic components contribute to the overall sen-
sor noise. MTJ bridge sensors, which operate on the
tunneling magnetoresistance effect, were fabricated
at NIST. MTJ devices consist of two magnetic
layers: a free layer and a fixed layer separated by
a thin insulator. The tunneling current through the
insulator is dependent on the relative orientation of

the two magnetic layers. These devices are used in
magnetic recording read sensors, MRAM bits, and

—-observed during free layer rotation and switching.
The disorder was a function of the MTJ preparation
technique. By incorporating a nano-oxide just be-
low the tunnel barrier (a technique developed in the
Materials Science and Engineering Laboratory) the
observed disorder was reduced. Time dependent
fluctuations in the magnetic structure, which are a
prime source of 1/fnoise, were directly observed
with dynamic Lorentz microscopy.

m= Narrow Switching Distributions in Na-
noscale Patterned Media — Magnetic nanodots



J. W. Ekin, N. Cheggour, M. Abrecht, C. Clickner, M. Field, S.
Hong, J. Parrell, and Y.-Z. Zhang, “Compressive Pre-Strain in
High-Niobium-Fraction Nb,Sn Superconductors,” IEEE Trans.
Appl. Supercond. 15, 3560-3563 (Tune 2005).

N.N. Martovetsky, P, Beuzzone, B. Stepanov, R. Wesche, C.-
Y. Gung, J. V. Minervini, M. Takayasu, L. F. Goodrich, J. W.
Ekin, and A. Nijhuis, “Effect of Conduit Material on CWX
Performance Under High Cycling Loads,” IEEE Trans. Appl.
Supercond. 15, 1367-1370 (June 2005).

J. W. Ekin, “Superconductors: An Emerging Power Technol-
ogy,” LOth Gaseous Dielectrics Conference, L. G. Chrisophorou,
J.K. Olthoff, and P, Vassiliou, Eds., Springer-Verlag, Berlin,
pp. 423-432 (2004).

Y-Z. Xuand J, W. Ekin, “Tunneling Characteristics and Low-
Frequency Noise of High-7, Superconductor/Noble-Metal
Junctions,” Phys. Rev. B 69, 104515 (March 2004).



shorter than the wavelength, 10 to 100 nm, will allow the permittivity, permeability, and conductivity to
be engineered and controlled to have new functionalities. Examples of such materials engineering include
light- and field-tunable exchange coupling, low loss amorphous/nanoparticle composites, negative-ep-
silon negative-mu (“left handed”) systems, and ferroelectric-ferromagnetic multilayers. Measurements
will be conducted on state-of-the-art, 100 gigahertz microwave test systems and cryogenic microwave
probe stations.

Mo .ecu.ar AND NANOMAGNETISM
S. E. Russek

Ultrasmall magnetic structures will be fabricated using both conventional nano-lithography techniques
(electron-beam and scanned-probe lithographies) and chemical synthetic techniques. The systems studied
may include molecular nanomagnets (e.g., Mn-12), carbon nanotubes grown on magnetic nanoparticles,
patterned longitudinal and perpendicular media, and nanodevices. The goal of this research will be to
understand the physics of ultrasmall magnetic structures, their implications for the limits of magnetic
data storage, and to develop novel nanoscale devices. The magnetization and switching processes will
be studied as a function of size, shape, and temperature to characterize thermally activated and quantum
mechanical tunneling transitions. The high-frequency properties (1 gigahertz to 150 gigahertz) will be
studied with high-frequency electron spin resonance, ferromagnetic resonance, and transport properties.
The molecular nanomagnets and magnetic nanostructures will be incorporated into thin-film device
structures to explore potential device applications.

Hicu-Speep Macnetic PHENOMENA
T. J. Silva

Experimental methods to determine fundamental limits to the data transfer rate of magnetic devices
are being developed. Both low-coercivity (“soft”) and high-coercivity (“hard”) magnetic materials are
studied. Experimental techniques include electrically sampled inductive detection and time-resolved
magneto-optics for the study of soft magnetic materials. Quantitative Kerr microscopy is used for the
measurement of switching speed in hard magnetic materials. Extensive facilities include a 20-gigahertz
sampling oscilloscope, a 50-femtosecond mode-locked Ti:sapphire laser, and a digital Kerr microscope
with a high-performance chilled charge-coupled device camera. Commercial and experimental solid-
state instrumentation is used for the generation of microwave pulses. Waveguide technology is employed
to deliver subnanosecond magnetic field pulses to samples. Waveguide structures are lithographically
fabricated on site in a state-of-the-art cleanroom, which includes mask generation facilities. Applicants
are encouraged who have a strong experimental background in magnetism, especially high-frequency
magnetic phenomena such as ferromagnetic resonance.

NonuINEAR Macneto-Optics
T. J. Silva

The second-harmonic magneto-optic Kerr effect (SHMOKE) is under investigation as a tool for the study
of interfacial magnetism. SHMOKE shows strong sensitivity to the magnetization at optically accessible

interfaces between ferromagnetic and non-ferromagnetic films, yet SHMOKE does not require exotic
facilities, such as ultrahigh vacuum (UHV) or synchrotron radiation. Therefore, SHMOKE shows great
promise as an industrial diagnostic instrument for the optimization of giant magnetoresistive sensors
and magnetic tunnel junctions, where interfacial magnetism strongly influences device performance.
SHMOKE also exhibits a strong magneto-optic signal, with the magnetic contrast approaching 60 per-
cent in some sample systems. Extensive resources for the study of SHMOKE include a mode-locked.
50-femtosecond Ti:sapphire laser, coincident photon detection electronics, photo-elastic modulators,
lock-in amplifiers, and sample translation stages. Samples may be produced on site with a state-of-the-art,
eight-source UHV sputtering system. Applicants are preferred with a strong experimental background in
magnetic thin films, magnetic multilayers, magneto-optics, and/or nonlinear optics.



Technical Contact:
Perry Wilson

Staff-Years (FY 2006):
3.0 professionals

ELECTROMAGNETIC CompPaTIBILITY:
REFERENCE FiELps AND PROBES

Goa.s

The Reference Fields and Probes Project develops
methods and techniques for establishing con-
tinuous-wave electromagnetic (EM) reference
fields and transfer probes for frequencies to 100
gigahertz. It maintains the capability to provide
antenna, probe, and field measurements with in-
ternational comparability and traceability to NIST
in support of U.S. industry. Although most present
applications utilize spectra in the 1 megahertz to
10 gigahertz range, systems such as automotive
collision avoidance radars that operate up to nearly
100 gigahertz are being developed.

Customer NEEps

Based on the principles of “one product, one techni-
cally valid international standard, one conformity
assessment” (1998 MSL Strategic Plan), industry
requires EM field measurement capabilities and
transfer probes that are traceable to NIST in order
to meet multinational compliance requirements
and reduce barriers to worldwide acceptance of
USS. products. We address these needs with the
following:

Reference Fields — Well defined EM reference
fields are necessary for the calibration of antennas
and probes. They are also needed for research and
development to increase measurement accuracy
and spectral range as will be necessary to support
the future needs of U.S. industry and private test
laboratories.

Field Probes — Accurate field probes are needed
by government and industry to define EM field
levels. U.S. defense and homeland security agen-
cies rely heavily on EM systems for sensors and
strategic communication. New probes need to be
developed for the ever-expanding range of EM
environments.

Probe Calibrations — Field probe calibrations
are costly. Techniques to reduce calibration costs
are needed, especially for applications that require
multiple probes and frequent recalibration.

TECHNICAL STRATEGY

We maintain an integrated effort both to generate
standard reference fields and to develop the probes
required for their accurate measurement. The two
efforts complement each other and allow cross

checking in order to reduce the uncertainties inher-
ent in each effort as well as to transfer calibration
capabilities to other test laboratories and facilities.
As instrumentation and electronics achieve higher
clock rates, measurements are needed at higher
frequencies. We are working both to extend cur-
rent techniques and facilities to higher frequen-
cies and to develop new test methods to increase
accuracy and reduce measurement costs. In this
context, we plan to develop improved methods for
measuring radio frequency (RF) emissions above
1 gigahertz.

Open area test site (OATS) facilities are accepted
as standard sites for electromagnetic compatibility
(EMC) emissions measurements. We are work-
ing on improvements of antenna characterization
through tighter standards documentation, updated
technology and enhanced methodology for EMC
antenna measurements. We work closely with the
American National Standards Institute (ANSI)
and the Society of Automotive Engineers (SAE)
to further improve their methods for EMC antenna
measurements.

Fully anechoic chamber (FAC) facilities are ac-
cepted as standard sites for free-space measure-
ments. Time-domain techniques are being studied
as a way to measure the characteristics of these
rooms and to improve the results obtained within.
This type of chamber is also being evaluated for
EMC product testing up to 40 gigahertz.

Closed test systems such as transverse electromag-
netic (TEM) cells have been widely adopted for
testing small antennas, sensors, and probes, but
are normally limited by geometrical constraints to
frequencies below 1 gigahertz. We are currently
constructing a new closed-cell system that utilizes
aco-conical geometry that can be used to test such
devices up to 45 gigahertz. The test volume of this
system is large enough to calibrate several probes
at once. EM modeling and analysis using numerical
techniques such as finite-difference time-domain
are used to predict system performance for mul-
tiple probes.

Measurements performed by use of different equip-
ment and facilities such as OATS, TEM cells, FAC
and semi-anechoic facilities often yield different
results. We will focus on systematically investigat-
ing methods to reduce these variations and improve
agreement within the U.S. industrial community.



supplies. In addition, current ripple and spikes are
a greater problem for short-sample critical current
testing than for magnet operation because of the
smaller load inductance. Therefore, we need to
understand the effects of ripple and spikes on the
measured critical current (Z,) and “n-value,” the in-
dex of the shape of the electric field-current curve.
We focused on how ripple changes the n-value
and showed that, in terms of percentage change,
the effect of ripple on 7-value was about 7 times
that on J,. Interlaboratory comparisons often show
variations in n-value much larger than the variations
in I,. We examined models and use the measure-
ments on simulators to attempt to reproduce and
understand the effects observed in measurements
on superconductors. We believe that current ripple
and spikes are sources of differences in m-values
measured at different laboratories.

m New Method to Evaluate the Relative
Stability of Conductors — We recently started
measuring voltage versus magnetic field (V-H) on
Nb,Sn wires to assess their relative stability. Volt-
age versus current (V-J) at constant field is usually
measured to determine J,. Low-noise V-H measure-
ments were made at constant or ramping current
with the same electronic instruments, apparatus,
and sample mount as used in J, measurements.
High-performance Nb,Sn wires exhibit flux-jump
instabilities at low magnetic fields, and low-noise
V-H curves on these wires show indications of
flux jumps. /-H measurements also reveal that
less stable wires will quench (abruptly and irre-
versibly transition to the normal state) at currents
much smaller than J, at the lower magnetic fields.
This new method needs to be further understood
and may be standardized to ensure that it provides
accurate and reliable data.

StaNnpaRDs CommitTEES

m Loren Goodrich is the Chairman of IEC/TC
90, the U.S. Technical Advisor to TC 90, the
Convener of Working Group 2 (WG2) in TC 90,
the primary U.S. Expert to WG4, WGS5, WG6 and

m TEC61788-1 Superconductivity — Part 1: Criti-
cal Current Measurement —DC Critical Current of
Cu/Nb-Ti Composite Superconductors

m JEC61788-2 Superconductivity —Part 2: Criti-
cal Current Measurement —DC Critical Current of
Nb,Sn Composite Superconductors

m_ IEC 61788-3 Superconductivity — Part 3:
Critical Current Measurement — DC Critical Cur-
rent of Ag-sheathed Bi-2212 and Bi-2223 Oxide
Superconductor

m IEC 61788-4 Superconductivity — Part 4: Re-
sidual Resistance Ratio Measurement — Residual
Resistance Ratio of Nb-Ti Composite Supercon-
ductors

m IEC 61788-5 Superconductivity — Part 5:
Matrix to Superconductor Volume Ratio Measure-
ment— Copper to Superconductor Volume Ratio of
Cu/Nb-Ti Composite Superconductors

m= IEC 61788-6 Superconductivity — Part 6:
Mechanical Properties Measurement — Room
Temperature Tensile Test of Cu/Nb-Ti Composite
Superconductors

m IEC 61788-7 Superconductivity — Part 7:
Electronic Characteristic Measurements — Surface
Resistance of Superconductors at Microwave
Frequencies

m IEC 61788-8 Superconductivity — Part 8: AC
Loss Measurements — Total AC loss Measurement
of Cu/Nb-Ti Composite Superconducting Wires
Exposed to a Transverse Alternating Magnetic
Field by a Pickup Coil Method

m IEC 61788-9 Superconductivity — Part 9:
Measurements for bulk high temperature super-
conductors — Trapped flux density of large grain
oxide superconductors

m IEC 61788-10 Superconductivity — Part 10:
Critical Temperature Measurement — Critical
Temperature of Nb-Ti, Nb,Sn, and Bi-System
Oxide Composite Superconductors by a Resistance
Method

WG11, and the secondary U.S. Expert to WG1,
WG3, and WG7.

m Ted Stauffer is Administrator of the U.S. Tech-
nical Advisory Group to TC 90.

STANDARDS

Inrecent years, we have led in the creation and revi-
sion of several IEC standards for superconductor
characterization:

w IEC 61788-11 Superconductivity = Part:
Residual Resistance Ratio Measurement — Residual
Resistance Ratio of Nb,Sn Composite Supercon-
ductors

m_ IEC 61788-12 Superconductivity — Part 12:
Matrix to Superconductor Volume Ratio Measure-
ment — Copper to Non-Copper Volume Ratio of
Nb,Sn Composite Superconducting Wires



range within a large dynamic range rather than at a
single signal level, thereby improving calibration
accuracy within the measurement interval. These
artifacts should be useful in a nationwide measure-
ment-comparison program.

Sample set of calibration dihedrals.

m RCS Uncertainty Analysis — We have
completed a measurement-based RCS calibration
uncertainty analysis for the Etcheron Valley Range,
NAVAIR, China Lake, CA. This study determined
the calibration uncertainty bounds without having
to rély on statistical model assumptions that may
not be valid for RCS calibrations and measure-
ments.

= Polarimetric Calibrations — RCS ranges
have reported less-than-satisfactory results with
existing polarimetric calibration procedures. We
developed a more robust calibration procedure
wherein full polarimetric data are obtained using
a dihedral rotating around the line-of-sight to the
radar, The new procedure allows us to: (1) improve
the signal-to-noise ratio and check for alignment
problems by exploiting the symmetry properties of
the dihedral, (2) correct for the overall angular bias
in the rotation angle, and (3) remove the effects of
drift to obtain drift-free system parameters.

REeceENT PuBLiIcATIONS

L, Muth “Cross-Polarization Parameters in the Presence of Drift
in Radar Cross Section Measurements,” Proc. Antenna Meas.
Tech. Assoc. (AMTA), Austin, TX, (October 2006) (in press).

L.A. Muth, C. M. Wang, and T. Conn, “Robust Separation of
Background and Target Signals in Radar Cross Section Mea-
surements,” JEEE Trans. Instrum, Measure. 54, 2462-2468
(December 2005).

L. Muth, C. Williams, D. Morales, and T. Conn, “Angular Er-
rors in Polarimetric Radar Cross Section Calibration Using a
Rotating Dihedral,” Proc. Antenna Measurement Techniques
Assoc. (AMTA), Providence, RI (October 2005).

L. Muth, C. Johnson, D, Morales, and T. Conn, “Angular Errors
in Polarimetric Radar Cross Section Calibration Using a Rotat-
ing Dihedral,” NIST Technical-Note 1539 (April 2005).

L, Muth, D. Diamond, and J. A. Lelis, “Uncertainty Analysis of
Radar Cross Section Calibrations at Etcheron Valley Range,”
NIST Technical Note 1534 (September 2004).



Hie

probe material properties on the micrometer and
nanometer scales. Many of these novel methods
employ the use of micromechanical cantilevers
to achieve the desired sensitivity. Because these
experiments are limited by the thermal noise of
the cantilever itself, low temperatures often must
be used, making the results less relevant to indus-
trial applications. Thus, there is a strong demand
for microcantilevers that are sensitive enough to
obtain useful results at room temperature. A further
complication arises when the experiments require
that a micrometer-sized magnetic material be
placed onto the cantilever. Doing this on an indi-
vidual basis is not only time-consuming, but it also
jeopardizes the uniformity and consistency of the
results. Therefore, there is a clear need to develop a
process to batch-fabricate ultrasensitive cantilevers
with magnetic dots prealigned and deposited as part
of the microfabrication process.

We have developed a process to meet these de-
mands. Careful consideration was given to the
design of the oscillator shape, and finite-element
modeling was used to study the resonant shapes and
to make sure that the resonance frequencies were in
the desired ranges for the specific applications. Our
ultrathin (less than 1 micrometer) single-crystal
silicon cantilevers with integrated magnetic struc-

Ipper torsion

Scanning electron micrographs of the double torsional
oscillator geometry. (a) A typical chip containing 12
devices, all with double-side access. (b) A closer view
of a double torsional oscillator with a 5 micrometer by
5 micrometer by 30 nanometer film on the head. The
illustration on the right side indicates the shape of the
two main torsional modes of operation.

tures are the first of their kind. They were fabricated
with a novel high-yield process in which magnetic
film patterning and deposition are combined with
cantilever fabrication. These novel devices have
been developed for use as cantilever magnetom-
eters and as force sensors in nuclear magnetic
resonance force microscopy. These two applica-
tions have achieved nanometer-scale resolution
with these cantilevers. Current magnetic moment
sensitivity achieved for the devices, when used as
magnetometers, is 10-'S ampere meter squared at
room temperature, which is more than a thousand-
fold improvement in sensitivity compared to con-
ventional magnetometers. Finite element modeling
was used to improve design parameters, ensure that
the devices meet experimental demands, and cor-
relate mode shape with observed results. The pho-
tolithographic fabrication process was optimized,
yielding an average of 85 percent and alignment
better than 1 micrometer. Post-fabrication focused
ion-beam milling was used to further pattern the
integrated magnetic structures when nanometer
scale dimensions were required.

m MEMS In-Situ Magnetometers to Mea-
sure Interlayer Coupling in Fe/Cr/Fe Trilayers
— The characterization of thin magnetic films,
patterned recording media, and nanometer-scale
magnetic devices has proven to be a challenge
for conventional magnetometers at nanoscale
and atomic dimensions. The limitation on the
sensitivity of magnetic moment sensors used in
these instruments is fundamentally understood by
comparing the energy necessary to excite the sen-
sor relative to the energy necessary to excite the
specimen for measurement purposes. Conventional
magnetometers are designed for measurements of
large specimens and therefore have a relatively low
signal-to-noise ratio for small specimens. Sensitiv-
ity can be improved tremendously by integrating
the specimens with the measurement sensor using
microfabrication methods. Further, ex-sifu mea-
surements outside of the growth chamber require
sample transfer, so there is the potential for sub-
stantial oxidation of thin films and devices.

We have tailored an ultrasensitive magnetometer
for the in-situ study of thin-film interface magne-
tism and interlayer magnetic exchange coupling.
The magnetometer is based on a customized mi-
cro-resonator made with silicon MEMS fabrication
techniques. The measured changes in magnetic
moments using the MEMS magnetometer were
compared to theoretical calculations and measure-
ments made by more conventional methods. In



Macnetopynamics, Spin ELecTRONICs, AND Macnetic NaNostrucTuRES

The program in magnetodynamics and spin electronics undertakes experimental research on
fundamental aspects of magnetization switching, precession, and damping at the nanoscale for
applications in magnetic information storage (such as magnetoresistive read heads, recording
media, and magnetic random-access memory) and magnetic devices (such as oscillators driven
by the transfer of quantum-mechanical electron spin angular momentum to magnetic films).

Maenetic Resonance AND MicRomECHANICAL Systems FOR BIOMAGNETIC
ImaciNnG AND MetroLocy

This program is developing new metrology and standards for biomedical imaging based on
magnetic resonance, magnetic nanoparticles, and low field sensing of biomagnetic fields. Micro-
mechanical and magnetic resonance systems are being developed to characterize nanomagnetic
systems and their use for measuring, detecting, and manipulating biomolecules for health and
national security applications.



Technical Contact:
Jim Baker-Jarvis

Staff-Years (FY 2006):

3.8 professionals
0.2 technician

ELECTROMAGNETIC PROPERTIES OF MATERIALS

Goats

The primary objectives of this program are to
develop, improve, and analyze relevant measure-
ment methods, uncertainties, and the underlying
physics of the complex permittivity and perme-
ability of bulk to nanoscale, naturally occurring and
artificial materials in the radio-frequency through
terahertz-wave spectrum as functions of tempera-
ture, frequency, and bias fields. The emphasis is
on the metrology of substrates, thin films, liquids,
biological materials, artificial materials, all at high
frequencies and small scales.

Customer NEEDS

As microprocessor speeds steadily increase and
new high-frequency technologies come on-line
there is a continual and essential need for high-fre-
quency materials characterization. Industries and
researchers require new measurement methods on
a broad array of materials with well characterized
uncertainties, at microwave frequencies through
terahertz, and over a range of temperatures. In
addition to applications involving traditional bulk
materials, trends in microwave materials are mov-
ing toward thinner layered substrates, biological
materials, artificial dielectrics, and nanoscale
materials.

At present, the frequencies of primary interest to
the microelectronic industry are peaked in the 5 to
10 gigahertz region, but satellite communications,
radars, and homeland security applications now
use much higher frequencies, up into the terahertz
bands. The primary driver for dielectric measure-
ments in the microelectronics arena originates in
the fact that as the operational speeds of devices
increase, the dielectric losses in substrate materials
severely influence microcircuit operation through
signal degradation and heating.

Microelectronic circuitry is packaged on multi-
layered substrates and thin films. Electronic sub-
strate/thin film materials are used in printed wiring
boards (PWB), low-temperature cofired ceramics
(LTCC), central processing unit (CPU) chips, and
microwave components. The dielectric parameters
influence the propagation speed, impedance, heat-
ing, and phasing characteristics of the substrates.
In order to achieve circuit miniaturization, new
substrates are being developed that incorporate
artificial, tunable, and layered structures. Emerging
substrates that exhibit electrical properties that do

not occur in naturally occurring materials are being
designed with metamaterials and nanoscale com-
posites. Such materials can provide novel device
concepts useful to the commercial, military, and
metrological communities. This field is in serious
need of metrology, and each of these materials
requires new measurement methods and well
characterized uncertainties. Newly developed thin
film materials such as high-temperature supercon-
ductors, ferroelectrics, and magnetoelectrics hold
great potential for improved functionality in micro-
wave devices, but are still in the critical stage of
materials development. Accurate characterization
at this stage of the microwave properties of these
emerging materials can have a large impact on the
development of future electronic systems.

Security needs and biological research require
high-frequency characterization of liquids. Hence,
the need for reference liquids and basic metrology
has increased. Both solid and liquid dielectric refer-
ence materials are needed to provide measurement
traceability to NIST. Measurement comparison
provides assessments of the quality of material
characterization.

Data on temperature-dependent dielectric and loss
properties of ceramics, substrates, and crystals from
cryogenic temperatures to 300 degrees Celsius, at
microwave and millimeter frequencies, are crucial
in the wireless and the time-standards arena. For
example, computer-based design methods require
very accurate data on the dielectric and magnetic
properties of these materials over wide ranges of
frequency and temperature. When interpreting
measurement results, an understanding of loss
mechanisms in low-loss crystals is important.
Meshing of an understanding of the underlying
physics with dielectric spectroscopy is becoming
increasingly important in novel material research.
In addition, nondestructive methods for permittiv-
ity measurement are needed throughout industry,

Various applications require composite dielectrics
that simulate the human body’s electrical properties
for security applications such as in metal detectors
and also for analyzing the effect of electromagnetic
interference (EMI) on implanted medical devices
and cell phones.

To support future needs in the microelectronics
industry for the development of novel new tech-
nologies, methods for characterizing nanoscale



THERMAL INSTABILITY OF MaGnetic THIN Fitms
T. J. Silva

As the grain size of thin-film magnetic recording media steadily decreases with increasing areal capacities,
we are concerned that recorded information may be erased as a result of thermally activated switching
of the individual grains — the so-called “superparamagnetic limit.” Our goal is to understand the fun-
damental mechanisms that result in thermal erasure through the measurement of various phenomena,
including magnetic viscosity and the time dependence of coercivity. Emphasis is placed on determining
the thermal stability of media over a wide range of time scales, from those accessible with large-scale
magnetometers to those that use pulsed microwave fields. The final goal is a measurement technique
for the determination of data stability in media without resorting to mean-time-before-failure analysis.
Extensive facilities include numerous magnetometers (vibrating-sample magnetometer, alternating gradi-
ent magnetometer, SQUID magnetometer), a transmission electron microscope for the determination of
grain size, and a state-of-the-art, eight-source, ultrahigh-vacuum sputtering system for the preparation
of samples. Applicants with a strong experimental background in magnetism — especially magnetic
thin-film preparation and characterization — are encouraged to apply.

ics and Elect



Macenetic Devices AND NANOSTRUCTURES

Goats

The Magnetic Thin Films and Nanostructures
Project develops measurements and standards for
nanomagnetic materials and devices used in the
magnetic data storage, magnetoelectronics, and
biomedical industries. These measurements and
standards assist industry in the development of
advanced magnetic recording systems, magnetic
solid-state memories, magnetic sensors, magnetic
microwave devices, and biomedical materials and
imaging systems. Broadband electrical measure-
ments are being developed to characterize na-
noscale devices based on giant magnetoresistance
(GMR), tunneling magnetoresistance (TMR),
and spin-momentum transfer (SMT). Magnetic
resonance techniques, such as high-frequency elec-
tron paramagnetic resonance (EPR) and nuclear
magnetic resonance (NMR) are being used to
study the properties of nanomagnets to improve
magnetic resonance imaging (MRI) or find applica-
tions in nanotagging. We are developing dynamic
nanoscale magnetic imaging, such as time-resolved
Lorentz microscopy in collaboration with the Mate-
tials Science and Engineering Laboratory, to better
understand the operation of nanoscale magnetic
structures and devices.

structures on nanometer-size scales and over a wide
range of time scales varying from picoseconds to
years. For example, the response of a 50-nanometer
magnetic device, used in a read head or a magnetic
random-access memory (MRAM) element, may
be determined by a 5-nanometer region that is
undergoing thermal fluctuations at frequencies of
1 hertz to 10 gigahertz. These fluctuations give rise
to noise, non-ideal sensor response, and long-term
memory loss. Spintronic devices and nanomagnetic
materials are finding applications in other areas
such as homeland security and biomedical imaging.
These industries require better low-power mag-
netic field sensors for weapons detection, chemical
detection, and magnetocardiograms, and require
novel nanomagnetic materials for MRI contrast
agents and defense applications.

Advances in technology are dependent on the
discovery and characterization of new effects such
as GMR, TMR, and SMT. Detailed understanding
of spin-dependent transport is required to optimize
these effects and to discover new phenomena that
will lead to new spintronic device concepts. New
effects such as spin momentum transfer and coher-
ent spin transport in semiconductor devices may
lead to new classes of devices that will be useful
in data storage, computation, and communications
applications. Many technologies require, or are
enabled by, the use of magnetic nanostructures
such as molecular nanomagnets. The study of
magnetic nanostructures will enable data storage
on the nanometer scale, a better understanding of
the fundamental limits of magnetic data storage,
and new biomedical applications.

TECHNICAL STRATEGY

We are developing several new techniques to ad-
dress the needs of U.S. industries for characteriza-
tion of magnetic thin films and device structures on

Technical Contact:
Stephen Russek

Staff-Years (FY 2006):
1.0 professional
2.0 research associates

- NMR system (7 teslas, 300-megahertz) for-use in char—
acterizing MRI contrast agents.

Customer NEEDS

The data storage and magnetoelectronics industries
are developing smaller and faster technologies that
require sub-hundred-nanometer magnetic structures
to operate in the gigahertz regime. New types of
spintronic devices with increased functionality and
performance are being incorporated into data stor-
age and magnetoelectronic technologies. New tech-
niques are required to characterize these magnetic

nanometer size scales-and gigahertz frequencies-

Device MacGNnetopynamics

We fabricate test structures for characterizing
small magnetic devices at frequencies up to 40
gigahertz. The response of submicrometer mag-
netic devices such as spin valves, magnetic tunnel
junctions (MTJs), and GMR devices with current
perpendicular to the plane is measured in both the
linear-response and nonlinear-switching regimes.
The linear-response regime is used for magnetic-
recording read sensors and high-speed isolators,
whereas the switching regime is used for writing



resonance excitation of a sample attached to a microcantilever at the cantilever’s resonance frequency.
Our goal is to optimize these novel detectors for biological applications, including in-vivo imaging of
cell organelles and membranes. The main challenge is to develop integrated microsystems with micro-
fabricated DC and RF field sources, magnetic sensors, and field gradient coils. Ideally, the chip should
be adaptable to microfluidic environments.

Micro-ELecTRoMECHANICAL Systems FoR METROLOGY
J. Moreland

We are developing micro-electromechanical systems (MEMS) with integrated components for precision
measurement purposes. Work focuses on the following goals: (1) improving the performance of funda-
mental standards instrumentation by developing novel detectors and more fully integrated measurement
systems, (2) exploring the impact of MEMS and MEMS-based metrology on the future development of
the microelectronics and data storage industries, and (3) improving the manufacturing yield with MEMS
probe assemblies designed for production line testing. Our cleanroom facility is fully equipped for bulk
and surface micromachining of silicon wafers including design, fabrication, and testing tools. We are
interested in all aspects of research including the development of novel MEMS structures, as well as the
testing and integration of MEMS structures into precision measurement instruments.

Nanosca_e Imacinc For Macnetic TECHNOLOGY
J. Moreland

The magnetic storage industry has advanced to the stage where nanometer-scale morphological and
physical properties play an important role in current and future disk drive performance, In its many
forms, scanned probe microscopy (SPM) can be used to measure roughness, device dimensions, elec-
tromagnetic field pattems, and various physical processes at nanometer scales, which provides important
information about the fundamental operation and limitations of drive components. Our goal is to help
tailor SPM techniques for these applications. We are investigating scanning tunneling microscopy, atomic
force microscopy, magnetic force microscopy, scanning potentiometry, and scanning thermometry for
their usefulness.

SINGLE-MoLecuLe ManipuLaTion AND MEASUREMENT
J. Moreland.

We are developing a nano-electromechanical system platform for single biomolecule manipulation and
measurement. Measurements to determine the structure and function of protein and DNA are currently
made using large populations of molecules rather than single molecules. Researchers in biotechnology
have shown that the behavior of single molecules in living systems can be different from results obtained
by measuring the statistical average of large populations of molecules. The limitation in making single
molecule measurements is primarily due to the lack of measurement tools and methods that are capable
of isolating, manipulating, and probing the behavior and structure of the molecules. As a result, there
is a rapidly growing interest in the development and application of nanotechnology to support single-
molecule measurements.

Spin Evectronics
W. H. Rippard, S. E. Russek, and T. J. Silva

Until recently, the only means known to control the magnetization state of ferromagnetic structures was
through the use of applied magnetic fields. However, within the last several years it has been demon-
strated that this can also be accomplished through the transfer of the electron spin angular momentum
from current-carrying electrons to the magnetization of magnetic films, generally referred to as the spin-
momentum-transfer effect. Spin transfer represents a fundamentally new way to control and manipulate
the magnetic states of devices, and allows hysteretic switching and coherent microwave dynamics to be
excited in magnetic nanostructures using a DC current. This project seeks both to understand the fun-
damental characteristics of the interaction between spin polarized currents and magnetic materials, and



APPENDIX E:
SYMBOLS FOR THE CHEMICAL ELEMENTS

Symbol Element Symbol Element Symbol Element
Ac Actinium Gd Gadolinium | Po Polonium
Ag Silver Ge Germanium =| Pr Praseodymium
Al Aluminum H Hydrogen Pt Platinum
Am Americium He Helium Pu Plutonium
Ar Argon Hf Hafnium Ra Radium.
As Arsenic Hg Mercury Rb Rubidium
At Astatine Ho Holmium Re Rhenium
Au Gold I Todine Rh Rhodium
B Boron In Indium Rn Radon
Ba Barium Ir Tridium Ru Ruthenium
Be Beryllium K Potassium 8 Sulfur
Bi Bismuth Kr Krypton Sb Antimony
Bk Berkelium La Lanthanum Sc Scandium
Br Bromine Li Lithium Se Selenium
Cc Carbon Lr Lawrencium | Si Silicon
Ca Calcium Llu Lutetium Sm Samarium
Cd Cadmium Md Mendelevium | Sn Tin
Ce Cerium. Mg Magnesium Sr Strontium
Cf Californium | Mn Manganese Ta Tantalum
Cl Chlorine Mo Molybdenum | Tb Terbium
Cm Curium N Nitrogen. Te Technetium
Co Cobalt Na Sodium Te Tellurium
Cr Chromium Nb Niobium Th Thorium
Cs Cesium Nd Neodymium | Ti Titanium
Cu Copper Ne Neon Tl Thallium
Dy Dysprosium | Ni Nickel Tm Thulium
Er Exbium No Nobelium U Uranium
Es Einsteinium {| Np Neptunium Vv Vanadium
Eu Europium (6) Oxygen WwW Tungsten
F Fluorine Os Osmium Xe Xenon
Fe Tron P Phosphorus Y Yttrium.
Fm Fermium Pa Protactinium | Yb Ytterbium
Fr Francium Pb Lead Zn Zine
Ga Gallium Pd Palladium Zr Zirconium,
Pm Promethium



nanometer-scale measurements can be calibrated
with reference to fundamental units. In particular,
the focus is on developing torque and force mag-
netometers, magnetic-resonance spectrometers,
and MRI microscopes on MEMS chips. Over the
long term, we expect that this technology will lead
to atomic-scale magnetic instrumentation for the
measurement and visualization of fundamental
magnetic phenomena.

MEMS Basep Macnetic Moment
Stanparp ReFerReNce MATERIALS

We are developing a method for defining the mag-
netic moment of a reference material based on a
torsional resonator with a patterned magnetic film
on its surface. Given accurate measurements of
the magnitude of the applied field, the moment of
inertia of the resonator, and the magnetic stiffen-
ing effect of the film on the resonance frequency
of the resonator, an absolute measurement of the
anisotropy energy and magnetic moment of the film
can be made independently. With this approach, the
anisotropy energy and the magnetic moment of the
film are measured directly, eliminating the need
for a detailed knowledge of the film’s saturation
magnetization or sample volume. Calibrated mo-
ments as small as 10~° ampere meter squared can
be measured. In principle, all of the measurements
needed for the reference material are traceable to
an atomic clock frequency reference.

Microrasricateo Rapio FREQUENCY
Tacs For MRI Trackine oF SINGLE
Ceus

We are developing a new biological detection
methods that would have application in two areas:
(1) to replace conventional serial fiuorescence-
based (and also more recently suggested optically
probed micro-metallic barcode) techniques with
a parallel detection scheme capable of simultane-
ously detecting multiple bio-agents without the
need for optical access to the system, and (2) to
improve the specificity of cell labeling strategies
for MRI. Custom designed magnetic micro-par-
ticle tags that induce distinct magnetic resonance
frequency shifts in the nuclear magnetic resonance
(NMR) of protons in water surrounding the labeled
biological agent are being microfabricated and
tested. Magnetic detection would be based on the
tag particle set being specifically tailored (in size,
shape, and composition using microlithography) to
give distinct NMR frequency shifts and resonance
line shapes. Such a magnetic resonance system
would enable noninvasive and inherently parallel
detection both in vitro and in vivo.

IntecRaTeD Cuip-Scace MRI
Microscopes

We are developing methods for integration of DC
and radio-frequency magnetic field sources and
MEMS cantilever oscillators to perform magnetic
resonance imaging and spectroscopy of small sam-
ples attached to the oscillators. The main goal is to
push the technology to measure magnetic phenom-
ena at the nanometer scale. Cantilevers operated at
resonance have the potential for detecting single
magnetic nanoparticle tags with 10° spins at room
temperature, and there are prospects for single
spin detection at low temperatures. Shrinking the
magnetic subsystems of a magnetic resonance
instrument into a chip-scale microsystem provides
benefits in terms of reduced size, batch fabrication
cost, and better performance via an increased detec-
tor bandwidth and sensitivity.

Cauipratep CANTILEVERS FOR
Force TRANSFER STANDARDS AT THE
NaNoNewTon RANGE

The ability to demonstrate traceable quantitative
measurement of forces in the regime below 10 mil-
linewtons is a tremendous challenge for a variety
of manufacturers. We are developing metrology for
use by primary, secondary, and industrial laborato-
ries to support quantitative measurement of these
forces. The goal is an instrument that incorporates
NIST’s force and length metrology to traceably
determine the spring constants of silicon reference
cantilevers and torsion oscillators. Silicon reference
cantilevers have been proposed by the Materials
Science and Engineering Laboratory as Standard
Reference Materials (SRMs) for calibrated adhe-
sion tests. Calibrated piezoresistive cantilever load
cells could ultimately serve as a standard reference
material for the dissemination of force to atomic
force microscopes (AFMs) and instrumented
indentation machines. Torsion oscillators may be
used as SRMs for magnetometers.

CanTILEVER SENSORS FOR INTRINSIC
Force MEasureEMENTS AT THE
FemToNewTon RANGE oF SINGLE
Mo ecutes

Among the experiments made possible by the revo-
lution in scanned probe microscopy, measurements
of bond rupture (forces between atoms), binding
rupture (forces between molecules), and molecular
conformation changes (force induced structural
changes of individual molecules) are perhaps the
most remarkable. Such forces might then serve as
intrinsic standards, effectively rendering this class



Mi ae

Macneto-MEcHanicaL MEASUREMENTS FOR HIGH

Current APPLICATIONS

Goats

This project specializes in measurements of the
effect of mechanical strain on materials for high-
current applications. Recent research has produced
the first electromechanical data for the new class
of high-temperature coated superconductors, one
of the few new technologies expected to have an
impact on the U.S. electrical power grid and the
large electric power industry. The project’s research
has also lead to the first four patents on contacts for
high-temperature superconductors.

Recent research also includes extending the high-
magnetic-field limits of electromechanical mea-
surements for development of nuclear-magnetic-
resonance (NMR) spectrometers operating at 23.5
teslas and 1 gigahertz, and the next generation of
accelerators for high-energy physics.

The Strain Scaling Law, previously developed by
the project for predicting the axial-strain response
of low-temperature superconductors in high mag-
netic fields, is now being extended to high com-
pressive strains for use in finite-element design of
magnet structures.

Project staff members in the laboratory for supercon-
ductor strain measurements.

NIST to provide performance feedback and engi-
neering data to companies and national laboratories
fabricating these conductors in order to guide their
decisions at this critical scale-up phase of coated-
conductor development.

The project serves industry primarily in two areas.
First is the need to develop a reliable measurement
capability in the severe environment of super-
conductor applications: low temperature, high
magnetic field, and high stress. The data are being
used, for example, in the design of magnets for
the magnetic-resonance-imaging (MRI) industry,
which provides invaluable medical data for health
care, and contributes $2 billion per year to the U.S.
economy.

The second area is to provide data and feedback to
industry for the development of high-performance
superconductors. This is especially exciting be-
cause of the large effort being devoted to develop
superconductors for grid reliability and enhanced
power-transmission capability. We receive numer-
ous requests, from both industry and government
agencies, for accurate electromechanical data to
help guide their efforts in research and develop-
ment in this decisive growth period.

TECHNICAL STRATEGY

Our project has a long history of unique measure-
ment service in the specialized area of electrome-
chanical metrology. Significant emphasis is placed
on an integrated approach. We provide industry
with first measurements of new materials in areas
where there is significant research potential.

ELeCTROMECHANICAL MEASUREMENTS OF
SupERCONDUCTORS

We have developed an array of specialized mea-

Technical Contact:
Jack Ekin

Staff (FY 2006):

1.0 professional

0.5 technician

2.0 research associates

Customer NEEDS

The recent success of the “second generation” of
high-temperature superconductors has brought with
it new measurement problems in handling these
brittle conductors. We have the expertise and equip-
ment to address these electromechanical problems.
Stress and strain management is one of the key
technology areas needed to move the second-gen-
eration high-temperature coated conductors to the
market place. The project utilizes the expertise and
unique electromechanical measurement facilities at

urement systems -to-test-the-effects-of mechanical.
stresses on the electrical performance of supercon-
ducting materials. Extensive, advanced measure-
ment facilities are available, including high-field
(18.5 teslas) and split-pair magnets, servohydraulic
mechanical testing systems, and state-of-the-art
measurement probes. These probes are used for
research on the effects of axial tensile strain and
transverse compressive strain on critical current,
measurement of cryogenic stress-strain characteris-
tics, composite magnetic coil testing, and variable-
temperature magnetoresistance measurements. Our



Suggested topics include printed circuit board radiation, signal integrity and coupling of high-speed digital
lines and devices, lossy transmission lines, characterization and optimal design of large test facilities
(e.g., reverberation, anechoic, and semi-anechoic chambers), properties of electromagnetic absorbing
materials, design of advanced composite and frequency selective materials, shielding effectiveness of
various materials, and other coupling problems. The broad objective is to develop accurate analytic and
numerical models that will advance the fundamental understanding of critical EMC/EMI issues. Extensive
measurement facilities are also available with which to assess the validity of the resulting models.

InDoor Rapio FREQUENCY PROPAGATION CHARACTERIZATION FOR BROADBAND
Wiretess: Mope.inc AND MEASUREMENTS
C. L. Holloway

Research for accurate characterization of general indoor propagation environments is important for the
design of future wireless communications systems. It is essential to understand the efficacy of broadband
wireless communications systems in office complexes and other types of building environments. The
indoor radio propagation channel is a very complicated environment with a variety of propagation issues
that must be defined and understood. Our research objective is to develop competence in the area of
indoor and indoor-to-outdoor radio propagation, and the effects on wireless communications systems. A
particular goal is to develop propagation models that will address the needs of the telecommunications
industry as related to the design of state-of-the-art wireless systems that can be utilized in indoor envi-
ronments. This will generally be accomplished by developing theoretical models and then designing and.
conducting experiments for the purposes of characterizing the indoor radio frequency (RF) propagation
environment. This will lead to analytical tools that can be used by wireless system designers. Advanced
computational tools, as well as excellent electromagnetic measurement facilities and instrumentation
are available for experimentation. Topics that need attention include coupling of energy into building
structures, propagation characterization of building materials, modeling of RF propagation into and within
building structures, and measurements techniques for characterizing building environments.

THEORETICAL DEVELOPMENT OF EQuivALENT GENERALIZED IMPEDANCE
Bounpary ConpITIoNs
C. L. Holloway

The interaction of electromagnetic fields with rough surfaces, composite materials, thin coatings, frequency
selective surfaces, and particle scattering are a few of the challenging problems of current theoretical
interest. Scattering problems of this type are complicated and usually require numerical techniques.
However, when the detailed surface features (roughness dimension, fiber dimensions in composites,
coating thickness, scattering shapes in frequency-selective surface, and particle spacing) are small com-
pared to a wavelength, equivalent generalized impedance boundary conditions (EGIBC) can be used.
These EGIBC and Maxwell’s equations are all that is needed to solve these types of scattering problems.
EGIBC are also very efficient in analyzing reflection problems. For example, in large electromagnetic
computational codes, the use of EGIBC can eliminate the need to spatially resolve the fine detail of a
particular scattering feature, which results in the abilities to solve much larger numerical problems.
The proposed research direction is to use various asymptotic techniques to derive EGIBC for various

electromagnetic field interactions. Specific boundary conditions will be derived so that the coefficients
in the EGIBC can be interpreted in terms of electric and magnetic polarizability densities.

THEORY FOR ELECTROMAGNETIC INTERFERENCE PROBLEMS
C. L. Holloway and D. A. Hill

In spherical near-field scanning, probe pattern information and data measured at points on a spherical
surface are used to determine the fields of a test antenna anywhere beyond the measurement radius (es-
pecially in the far-field zone). Although the theory is well understood, a number of areas need further
work, including (1) development of more efficient measurement and computation methods; (2) analysis
of and correction for measurement errors; (3) practical pattern correction schemes for general probes;
(4) development of a simplified theory for the “quasi-far-field region,” where measurements are “al-



electromechanical test capability for superconduc-
tors is one of only a few in the world.

COLLABORATION WITH OTHER
GoverNnmeNT AGENCIES

These measurements are an important element of
our ongoing work with the U.S. Department of
Energy (DOE). The DOE Office of High Energy
Physics sponsors our research on electromechani-
cal properties of candidate superconductors for par-
ticle-accelerator magnets. These materials include
low-temperature superconductors (Nb,Sn, Nb,Al,
and MgB,), and high-temperature superconduc-
tors — Bi-Sr-Ca-Cu-O (BSCCO) and Y-Ba-Cu-O
(YBCO) — including conductors made on rolling-
assisted, biaxially textured substrates (RABiTS)
and conductors made by ion-beam-assisted de-
position (IBAD). Our research is also sponsored
by the DOE Office of Electric Transmission and
Distribution. Here, we focus on high-temperature
superconductors for power applications, including
power-conditioning systems, motors and genera-
tors, transformers, magnetic energy storage, and
transmission lines. In all these applications, the
electromechanical properties of these inherently
brittle materials play an important role in determin-
ing their successful utilization.

CHARACTERIZATION OF
Superconpuctors FoR ELEcTRIC
Power Grip RELIABILITY

Improved superconductors are being developed
by U.S. companies and demonstrated for power
transmission. Superconductors’ greater current
carrying capability is advantageous for upgrading
real-estate-limited transmission lines in cities. Su-
perconductors are also being developed for use in
superconductor magnetic energy storage (SMES).
Our work on characterizing superconducting prop-
erties at high stresses and high strains, and over
variable temperatures is critical for the develop-
ment of these superconductors. This work is also
supported by DOE.

Significant progress in second-generation super-
conductors was reported in 2005-2006. These thin,
highly textured YBCO films are deposited with
mainly non-vacuum techniques on flexible metal
substrates. They are now available in lengths of
over 300 meters, carrying very high currents of
over 2.5 to 3.0 mega-amperes per square centi-
meter at 77 kelvins. These superconductors have
the potential to replace and improve parts of the
ageing power grid in the United States. However,
with the first coils fabricated from second-gen-

eration conductors, manufacturers learned that the
layered architecture of the conductor may pose
a problem: delamination of the ceramic layers
under transverse tensile stress. This is important
for rotating machinery, because of the centrifugal
forces on the conductors, and more generally,
because differential contraction in coil structures
can place the conductors under severe transverse
tensile stresses.

Scauinc Laws ror Macnet Desicn

In the area of low-temperature superconductors,
we are generalizing the Strain Scaling Law (SSL),
a magnet design relationship we discovered two
decades ago. Since then, the SSL has been used in
the structural design of most large magnets, based
on superconductors with the A-15 crystal structure.
However, this relationship is a one-dimensional
law. We are developing a measurement system to
carefully determine the three-dimensional strain
effects in A-15 superconductors. The importance
of these measurements for very large accelerator
magnets is considerable. The SSL is also being
developed for high-temperature superconduc-
tors, since we recently discovered that practical
high-temperature superconductors also exhibit an
intrinsic axial-strain effect.

AccoMPLISHMENTS

m= New Apparatus Developed to Measure
Delamination in YBCO Coated Conductors
— Over the past two years we have measured
the delamination strength of second-generation
YBCO superconductors. This required the design
and construction of a new test apparatus. The test
fixture head of the apparatus consists of two anvils
made of Ni-Sat.%W, which is the same material as
the substrate of most coated conductors. The bot-
tom anvil is soldered to the substrate side of the
sample, while the top anvil is soldered to the silver
cap layer on top of the ceramic YBCO layer. The
choice of fabricating both anvils from the same
material as the substrate of the superconductor
ensures the absence of thermal shear stress between
the sample and the anvils when they are cooled
to 77 kelvins. The transverse tensile strength of
the conductor is measured in two steps. First, the
internal strength of the ceramic layers is measured,
without edge effects. Second, the overall strength
is measured, including edge effects. Edge damage
may arise from, for instance, slitting of the conduc-
tor to smaller widths (a common procedure in the
manufacturing process), and we anticipated that it
may play a role in initiating delamination.



Spin ELEcTRONICS

Goats

The Spin Electronics Project focuses on developing
measurements to better understand the interactions
between the electron spin in current-carrying elec-
trons and the magnetization of ferromagnetic films.
These measurements will allow the investigation
of magnetization dynamics at nanometer lengths
scales characterized by precession angles that are
orders of magnitude larger than previously acces-
sible. They will facilitate the development and con-
tinued scaling of spintronic devices. The techniques
developed as part of this program will support
industrial roadmaps that have targeted magnetic
disk drives with terabit-per-square-inch densities
and magnetic random-access memory (MRAM) at
the 65 nanometer node by the end of the decade.
In addition, these measurements will help industry
develop smaller and cheaper nanoscale magnetic
microwave devices that may replace much larger
and expensive on-chip microwave circuitry.

Customer NEEps

Until recently, the only means known to control
the magnetization state of ferromagnetic structures
was through the use of applied magnetic fields.
However, within the last several years it has been
demonstrated that this can also be accomplished
through the transfer of the electron spin angular
momentum from current-carrying electrons to the
magnetization of magnetic films, generally referred
to as the spin-momentum-transfer (SMT) effect.
Spin transfer represents a fundamentally new way
to control and manipulate the magnetic states of
devices, one that emerges only at the nanoscale. It
will allow investigation of magnetization dynam-
ics and spin-waves on length scales smaller than
previously possible. It creates the ability to switch
nanopatterned magnetic storage devices at speeds
not previously accessible. It presents opportunities
for the development of spin-switched MRAM and

operating at high frequencies. These measurements
will help industry develop future generation spin-
tronic devices and facilitate the continued scaling
of-magnetic data storage into the deep nanometer

‘range.

TECHNICAL STRATEGY

We are performing measurements on magnetic
nanostructures in order to investigate magnetiza-
tion dynamics at nanometer length scales and sub-
nanosecond time scales. The high-speed dynamics
and switching events are induced through the
spin-transfer effect, which utilizes the transfer of
the electron spin angular momentum in nanomet-
ric magnetic heterostructures to induce magnetic
excitations at length scales down to 10 nanometers
and at frequencies up to 100 gigahertz. We are
measuring the high frequency properties of the spin
transfer induced dynamics in patterned magnetic
nanostructures as well as dynamics that are induced
locally in continuous films.

We are trying to determine how spin-based ef-
fects can be avoided and exploited in magnetic
nanostructures in order to assist the magnetic data
storage industry and facilitate the development of
nanoscale microwave devices. We will quantify the
intrinsic device properties that determine the high
frequency dynamics of spin-transfer nanoscale
oscillators — such as oscillation frequency, line-
width, and power, which currently only qualita-
tively agree with theory — and develop measure-
ments to relate the stochastic (statistical) switching
characteristics of spin-switched MRAM to the
component materials properties. For example, we
are presently developing techniques to measure
the magnetic precessional damping parameter in
single, active devices with dimensions below 100
nanometers.

AccomPLISHMENTS

Technical Contact:
Bill Rippard

Staff-Years (FY 2006):
1.0 professional
2.0 research associates

active microwave devices operating above frequen-
cies of 100 gigahertz.

At present, the SMT effect is too poorly under-
stood to effectively exploit or diminish its effects
in practical devices, and little is accurately known
about the dynamics induced by the effect. We will
develop metrology to investigate and understand
how spin-based effects can be avoided or exploited
in magnetic nanostructures in order to assist the
magnetic data storage industry and to facilitate
the development of nanoscale microwave devices

= Injection Locking in Spin-Transfer Mi-
crowave Oscillators — Synchronization of
weakly coupled oscillators, generally referred to
as injection locking or frequency entrainment, has
numerous examples in nature and generally occurs
in oscillator systems having at least weak nonlin-
ear interactions. Examples range from biological
systems, such as the synchronized flashing of
fireflies and singing of certain crickets, to those in
the physical sciences, such as Josephson junction
arrays and the synchronization of the Moon’s rota-



Technical Contact:
Katie MacReynolds

Staff-Years (FY 2006):
2.0 professionals
1.0 technician

AANTENNAS AND ANTENNA SYSTEMS:
ANTENNA NeEar-Fic_p MEASUREMENTS

Goats

The Antenna Near-Field Measurements Project
serves as a national resource by providing antenna
measurement services and traceability through
calibrations. It supports government and private
industry programs, and maintains and develops
the standards, methods, and instrumentation for
antenna characterization of gain, polarization and
pattern measurements.

Customer NEEDS

We continue to upgrade antenna metrology capa-
bility to meet evolving customer demands in the
following areas:

Probe Characterization — Accurate probe char-
acterization is fundamental to precise antenna
measurements. We provide probe correction coef-
ficients for use in planar, spherical and cylindrical
near-field facilities.

Planar and Spherical Near-Field Measurements
— These are required to accurately characterize
large aperture, high-frequency antennas such as
phased array and dish antennas used in satellite
communications.

Antenna Standard Characterization — Industry
and government require antenna standards for in-
house antenna measurements.

Measurement Traceability — Program specifica-
tions often require NIST traceability.

Independent Verification of Antenna Param-
eters — Government and industry request mea-
surements to verify that their measurement and
analysis procedures produce the predicted and
correct results.

Technical Support — Assistance on measurement
techniques and analysis algorithms for antenna
facilities that are implementing near-field mea-
surements.

TECHNICAL STRATEGY

We currently maintain near-field antenna measure-
ment standards and capabilities for frequencies
from 1.5 to 110 gigahertz. The recent integration
of a laser tracker system provides accurate infor-
mation on probe position for use with position-
correction algorithms. These improvements will

nMnElecth

help maintain low uncertainties as measurement
frequencies are increased in the future.

We have extended the frequency range of our
extrapolation measurement capability. The new
extrapolation range provides on-axis gain char-
acterization capability to complement near-field
antenna pattern measurements at millimeter-wave
frequencies. Plans to provide polarization charac-
terization up to 110 gigahertz are in process and
will be available in the near future.

The NIST probe pattern range with the fixed probe
located near the center of the photo and the moving
probe located on the moving tower in the upper right.

We are performing an internal comparison on all
three of the NIST near-field ranges — planar, cy-
lindrical, and spherical — to verify performance
and refine uncertainties. Our capability with all
three types of ranges is unique.

ACCOMPLISHMENTS

m= Antenna Calibrations — We perform an-
tenna calibrations for external customers. Examples
of recent measurements are:

— WR-28 — open-ended waveguide probe
— WR-62— 3 standard gain horns

— WR-90 — 3 standard gain horns and an
open-ended waveguide probe

— WR-42 — 2 standard gain horns and
2 dual-port circularly polarized probes



switching and steady-state magnetic precession in
patterned magnetic nanostructures, nanowires, and
nanocontacts as well as current-induced motion of
magnetic domain walls. Theoretical efforts to better
understand these effects have included analytical
approaches, numerical single-domain modeling,
and micromagnetic simulations; a rough general
qualitative agreement between experiment and
theory regarding the most basic results has been
achieved. However, the measured precessional
dynamics in magnetic nanocontacts do not always
agree with the predictions of both micromagnetic
and single-domain modeling. For instance, mea-
surements show much more complicated evolution
of the precessional frequency with current and field
than predicted by single-domain simulations and
spin-wave theories.

We have measured the detailed dependence of
the oscillation frequencies, linewidths, and output
powers of spin-transfer nanocontact oscillators as
functions of applied field strength, bias current,
and angle of the applied magnetic field. For fields
applied only moderately out of the plane of the
film, the evolution of these properties is continuous.
However, for fields applied more strongly out of
plane they exhibit discontinuities in both current
and applied field. These discontinuities typically
correlate with changes in the device resistance,
changes in device output power, and a broadening
of their spectral linewidths. However, away from
these discontinuities, the oscillator output pow-
ers are larger and the linewidths narrower when
compared to geometries having the fields applied
at lower angles. Our measurements suggest that
the discontinuous evolution of the frequency with
current and applied field results from an abrupt
change in precessional trajectories of the magne-
tization in the free layer. Comparisons with present
theories give only qualitative agreement with our
experimental results.

fy.
z
g
z
2
of
3
e
2
c

0.9
Field (T)

Measured data from a spin-transfer nanoscale oscil-
lator comparing the measured device linewidth and
the evolution of the precession frequency with current
and magnetic field. The linewidth is shown as shading
mapped directly onto the frequency surface so that the
two parameters can be compared.

Awarp

US. Department of Commerce Silver Medal (Bill
Rippard, Stephen Russek, and Tom Silva) and
EEEL Distinguished Associate Award (Matt Pufall
and Shehzaad Kaka) for the discovery of mutual
phase-locking, external frequency-locking, and
frequency modulation of spin-transfer nano-oscil-
lators, 2006.

REcENT PUBLICATIONS

W. H. Rippard, M. R. Pufall, and 8. E, Russek, “Comparison
of Frequency, Linewidth, and Output Power in Spin Transfer
Nanocontact Oscillators” (submitted for publication).

M.L. Schneider, M. R. Pufall, W. H. Rippard, and S.B. Russek,
“Thermal Effects on the Critical Current of Spin Torque Switch
ing in Nanopillars” (submitted for publication).

J.M. Shaw, W. H. Rippard, 8. B. Russek, T, Reith, and C. M.
Falco, “Narrow Switching Field Distributions in Perpendicular
Magnetic Nanodot Arrays” (submitted for publication).

W. H. Rippard and M. R. Pufall, “Microwave Generation in
Magnetic Multilayers and Nanostructures,” in Handbook of
Magnetism and Advanced Magnetic Materials, John Wiley,
Sussex, U.K. (in press).

M.R. Pufall, W. H. Rippard, S. E. Russek, S. Kaka, and J. A.
Katine, “Electrical Measurement of Spin-Wave Interactions of
Proximate Spin Transfer Nanooscillators,” Phys. Rev. Lett. 97,
087206 (August 2006).

S. Kaka, M. R. Pufall, W. H. Rippard, T. J. Silva, S. E. Russek,
and J. A. Katine, Mutual Phase-Locking of Microwave Spin
Torque Nano-Oscillators, Nature 437, 389-392 (September
2005).

W.H. Rippard, M. R. Pufall, S. Kaka, T. J. Silva, S. E. Russek,
and J. A. Katine, “Injection Locking and Phase Control of
Spin Transfer Nano-Oscillators,” Phys. Rev. Lett. 95, 067203
(August 2005).

S. E, Russek, S. Kaka, W. H. Rippard, M. R. Pufall, and T. J.
Silva, “Finite-Temperature Modeling of Nanoscale Spin-Trans-
fer Oscillators,” Phys. Rev. B71, 104425 (March 2005).

M. R. Pufall, W. H. Rippard, 8. Kaka, T. J. Silva, and S. E.
Russek, “Frequency Modulation of Spin-Transfer Oscillators,”
Appl. Phys. Lett. 86, 082506 (February 2005).

S. Kaka, M. R. Pufall, W. H. Rippard, T. J. Silva, S. E. Russek,
J.A. Katine, and M. Carey, “Spin Transfer Switching of Spin
Valve Nanopillars Using Nanosecond Pulsed Currents,” J.
Magn. Magn. Mater. 286, 375-380 (February 2005).

W. H. Rippard, M. R. Pufall, S. Kaka, T. J. Silva, and S. E.
Russek, “Current-Driven Microwave Dynamics in Magnetic
Point Contacts as a Function of Applied Field Angle,” Phys.
Rev. B70, 100406 (September 2004),

M.R. Pufall, W. H. Rippard, S. Kaka, S. E. Russek, T. J. Silva,
J. Katine, and M. Carey, “Large-Angle, Gigahertz-Rate Random
Telegraph Switching Induced by Spin-Momentum Transfer,”
Phys. Rev. B 69, 214409 (June 2004).

W. H. Rippard, M. R. Pufall, S. Kaka, S. E, Russek, and T. J.
Silva, “Direct-Current Induced Dynamics in Co,,Fe,y/NiggFe,,
Point Contacts,” Phys. Rev, Lett, 92, 027201 (January 2004).



of instruments self-calibrating. We are developing
the needed femtonewton force sensors for the vari-
ous applications. For instance, an ultrathin cantile-
ver with an integral interferometric displacement
sensor is appropriate for use in the binding rupture
experiments since the unit must be compatible with
aqueous biological environments. For the metal
bond rupture experiments, a feedback-controlled
torsion balance using either electromagnetic or
electrostatic forces to provide the null compensa-
tion is more appropriate. These sensors will be
calibrated in an ultrahigh vacuum, atomic force
test and calibration apparatus in the Manufacturing
Engineering Laboratory and the single molecule
laser tweezers apparatus at JILA (jointly operated
by the University of Colorado and NIST).

Maenetic Templates FOR NANOMETER
Scace ManipuLaTioN AND ASSEMBLY OF
Maenetic ParticLes anp Devices

We are developing a nanometer scale assembly
platform based on an array of “switchable” mag-
netic dots for manipulating magnetic components.
Jn the current configuration, a magnetic force mi-
croscope (MFM) tip is used to distribute magnetic
polystyrene beads in an array of patterned Permal-
loy (Ni-Fe) traps on a thin membrane as part of a
microfluidic flow cell. We have demonstrated the
ability to translate particles with nanometer preci-
sion and sort micrometer sized magnetic particles
based on size differences in the array with the
MEM. In addition, we are currently developing
fluidic cells with the potential for large-scale in-
tegration based on “spin-valve” technology using
magnetically balanced spin-valve structures that
act as switchable permanent magnets with a fer-
romagnetic “on” or an antiferromagnetic “off” net
magnetization state so that magnetic particles in
the fluid cell can be electronically confined and
released for transporting, sorting, or assembly ap-
plications. Spin-valve magnetic traps and a matrix
addressable architecture similar to MRAM would
—then eliminate the need forascanning MEM tip for
translating particles. In principle, these techniques
would be the basis for nanometer scale robotic as-
sembly of components to achieve novel biological,
chemical, electrical, or mechanical functionality at
the single molecule level.

SincLe Motecuce Enzymotocy:
Mecnanics of REPLICATION

The structure of DNA and individual proteins
is being examined in increasing detail; however
our knowledge of the mechanics of their interac-
tions is often limited to bulk experiments. We are

developing a new single-molecule assay to assist
in elucidating the mechanics of enzyme activity.
The flexibility of this in-vitro assay will be used
to determine the operation of individual enzymes,
complementing existing genetic techniques. The
ultimate goal of this project is to work towards a
more complete understanding of the mechanics of
DNA polymerization and how errors in this process
can lead to a range of neurological diseases, even-
tually developing an in-vivo assay. To control and
manipulate the DNA substrate we will be working
with superparamagnetic beads in a microfluidic en-
vironment. By attaching a magnetic bead to one end
and applying a magnetic field we can stretch out
the DNA. This provides a static one-dimensional
template along which enzyme activity can be easily
observed for longer periods and correlated with the
underlying base-pair sequence.

MEMS Desien, FasrIcaTION, AND
PackacinG For Cuip-Scate Atomic
Cocks AND MaGNeETOMETERS

Many important electronic devices (such as global
positioning receivers, wireless receivers, portable
magnetometers, and compact gyroscopes and ac-
celerometers) would greatly improve if very small,
highly accurate, low-power, and low-cost measure-
ment references were available. These devices are
typically very large (often laboratory-scale), often
consume kilowatts of power or require cryogenic
cooling, and are generally too expensive for wide-
scale applications. The challenge is to shrink the
size of the sensors and standards based on atomic
properties from the laboratory scale (10 cubic me-
ters) to the 1 cubic centimeter scale of a computer
chip. While the chip-scale atomic clock (as an early
example of a chip-scale atomic device) is only
the size of a rice grain, it is a complex structure
comprised of more than a dozen components; more
advanced chip-scale atomic devices will likely be
more complex. We are developing new methods for
designing, fabricating, and assembling chip-scale

te d ptimized-for-different-appl
tions. A key part of the chip-scale atomic device
is the ultra-miniature atomic vapor cell containing
the active sensing atoms. We are developing new
technologies to design, fabricate, and assemble
these crucial vapor cells into various chip-scale
atomic device packages and applications.

ACCOMPLISHMENTS

ua Novel Fabrication of Micromechanical
Oscillators with Nanoscale Sensitivity at Room
Temperature — Over the past decade, several
experimental methods have been developed to



Electromagnetics Division

National Institute of Standards and Technology
325 Broadway

Boulder, Colorado 80305-3328

Telephone: (303) 497-3131
Facsimile: (303) 497-3122
On the Web: http://www.boulder.nist.gov/div818/

Any mention of commercial products is for information only; it does not imply recommenda-
tion or endorsement by the National Institute of Standards and Technology nor does it imply
that the products mentioned are necessarily the best available for the purpose.



Celsius) and 4.2 kelvins (the boiling point of liquid
helium). The value of RRR indicates the purity and
the low-temperature thermal conductivity ofa ma-
terial, and is often used as a materials specification
for superconductors. The low temperature resistiv-
ity of a sample that contains a superconductor is
defined at a temperature just above the transition
temperature or is defined as the normal-state
value extrapolated to 4.2 kelvins. For a composite
superconducting wire, RRR is an indicator of the
quality of the stabilizer, which is usually copper
or aluminum that provides electrical and thermal
conduction during conditions where the local su-
perconductor momentarily enters the normal state.
For pure Nb used in radio-frequency cavities of
linear accelerators, the low temperature resistivity
is defined as the normal-state value extrapolated
to 4.2 kelvins. This extrapolation requires precise
measurements. We have studied some fundamental
questions concerning the best measurement of RRR
and the relative differences associated with differ-
ent measurement methods, model equations for
the extrapolation, and magnetic field orientations
(when a field is used to drive the superconductor
into the normal state).

Macnetic Hysteresis Loss
MeasuREMENTS

As part of our program to characterize supercon-
ductors, we measure the magnetic hysteresis loss
of marginally stable, high-current Nb,Sn supercon-
ductors for fusion and particle-accelerator magnets.
‘We use a magnetometer based on a superconducting
quantum interference device (SQUID) to measure
the magnetic hysteresis loss of superconductors,
which is the area of the magnetization-versus-field
loop. In some cases, especially for marginally stable
conductors, we use special techniques to obtain ac-
curate results. Measurement techniques developed
at NIST have been adopted by other laboratories.

AccomPLISHMENTS
m= Superconductor Data Enables U.S. Com-

AUS. company turned to us for critical current
measurements at 20 kelvins to determine whether
its conductor could meet the project’s specifications
for critical current. Critical current, the largest
current a superconducting wire can carry, is a key
performance and design parameter. Critical current
depends on temperature, magnetic field, and, in
many cases, the angle of the magnetic field with
respect to the conductor.

We made variable-temperature critical-current
measurements on three wire specimens in mag-
netic fields up to 8 teslas, at various magnetic-
field angles, and at temperatures from 4 to 30
kelvins. NIST has the only such multiparameter,
high-current, variable-temperature measurement
capability in the U.S. The largest current applied
to the 0.81 millimeter diameter wire samples was
775 amperes.

The results showed that the angle dependence of
critical current for the wires was less than just 3 per-
cent over the useful range of field and temperature,
and that the round wires could be used at higher
magnetic fields and temperatures than tape con-
ductors. These data will be used to design the safe
operating limits of the SMES magnet system.

u T “Magnetic field |
(Tesias)
so
+ Os 4
1
Be
es
4 4
he
8

Critical Current (Amperes)

y
=]
Ss

10 20
Temperature (Kelvins)

pany to Offer Product to Korean Project —New
bismuth-based high-temperature superconductor
wires are under active consideration for a 600 ki-
lojoule superconducting magnetic energy storage
(SMES) project lead by the Korea Electrotechnol-
ogy Research Institute. The purpose of the SMES
system is to stabilize the electric power grid. The
magnet will be wound with 10-kilo-ampere super-
conducting cables composed of many round wires.
It will be cooled to 20 kelvins by cryocoolers.

Critical current versus temperature of a high-T,
Bi,Sr;CaCu,O,,, wire at various magnetic fields. Such
curves are used to determine the safe operating cur-
rent at different temperatures and fields.

= Key Measurements for the International
Thermonuclear Experimental Reactor — Su-
perconducting magnets are used in fusion energy
projects, such as the International Thermonuclear
Experimental Reactor (ITER), to confine and heat



STANDARDS FOR SUPERCONDUCTOR AND MAGNETIC
MEASUREMENTS

Goats

This project develops standard measurement tech-
niques for critical current, residual resistivity ratio,
and magnetic hysteresis loss, and provides quality
assurance and reference data for commercial high-
temperature and low-temperature superconductors.
Applications supported include magnetic-reso-
nance imaging, research magnets, magnets for fu-
sion confinement, motors, generators, transformers,
high-quality-factor resonant cavities for particle
accelerators, and superconducting bearings. Su-
perconductor applications specific to the electrical
power industry include transmission lines, synchro-
nous condensers, magnetic energy storage, and
fault-current limiters. Project members assist in the
creation and management of international standards
through the International Electrotechnical Commis-
sion for superconductor characterization covering
all commercial applications, including electronics.
The project is currently focusing on measurements
of variable-temperature critical current, residual
resistivity ratio, magnetic hysteresis loss, critical
current of marginally stable superconductors, and
the irreversible effects of changes in magnetic field
and temperature on critical current.

Probe for the measurement of the critical current ofa
superconductor wire as a function of temperature, The
probe is inserted into the bore of a high field supercon-
ducting magnet.

and research magnets makes this technology es-
pecially important. We focus on: (1) developing
new metrology needed for evolving, large-scale
superconductors, (2) providing unique databases
of superconductor properties, (3) participating
in interlaboratory comparisons needed to verify
techniques and systems used by U.S. industry, and
(4) developing international standards for super-
conductivity needed for fair and open competition
and improved communication.

Electric power grid stability, power quality, and
urban power needs are pressing national problems.
Superconductive applications can address many of
them in ways and with efficiencies that conven-
tional materials cannot. “Second-generation” Y-Ba-
Cu-O (YBCO) superconductors are approaching
the targets established by the U.S. Department of
Energy. The demonstration of a superconductor
synchronous condenser for reactive power support
was very successful and has drawn attention to the
promise of this technology. Previous demonstration
projects had involved first-generation materials,
Bi-Sr-Ca-Cu-O (BSCCO). Variable-temperature
measurements of critical current and magnetic
hysteresis loss will become more important with
these AC applications, and methods for reducing
losses are expected to evolve as second-generation
materials become commercial.

Fusion energy is a potential, virtually inexhaustible
energy source for the future. It does not produce
CO, and is environmentally cleaner than fission
energy. Superconductors are used to generate the
ultrahigh magnetic fields that confine the plasma in
fusion energy research. We measure the magnetic
hysteresis loss and critical current of marginally
stable, high-current Nb,Sn superconductors for
fusion and other research magnets. Because of the
way superconductors are used in magnets, vari-

Technical Contact:
Loren Goodrich

Staff-Years (FY 2006):
1.0 professional
0.7 technician

Customer NEEDS

This project serves the U.S. superconductor indus-
try, which consists of many small companies, in the
development of new metrology and standards, and
in providing difficult and unique measurements. We
participate in projects sponsored by other govern-
ment agencies that involve industry, universities,
and national laboratories.

The potential impact of superconductivity on
electric power systems, alternative energy sources,

able-temperaiure critical-current Measurements ave
needed for more complete characterization.

The focus of high-energy research is to probe and
undérstand nature at the most basic level, includ-
ing dark matter and dark energy. The particle
accelerator and detector magnets needed for this
fundamental science continue to push the limits of
superconductor technology. The next generation of
Nb,Sn and Nb-Ti wires is pushing towards higher
current density, less stabilizer, larger wire diameter,
and higher magnetic fields. The resulting higher



m= = Wafer-Level Fabrication and Filling of
Cesium Vapor Cells for Chip-Scale Atomic
Devices — The introduction of atomic vapor sys-
tems to MEMS has enabled a new class of hybrid
microchips referred to as chip-scale atomic devices
(CSADs) with integrated optical, radio-frequency,
electronic, and quantum based atomic compo-
nents. At the heart of a CSAD is a miniature cell
containing alkali vapor. Suitable techniques for
fabricating vapor cells must be developed such that
they will not only be in a physical form suitable
for integration into the rest of a MEMS assembly,
but also in a manner that is amenable to true wa-
fer-scale mass production. Whereas conventional
cells are made by glass blowing, millimeter scale
vapor cells are more easily fabricated by means
of standard photolithography, silicon etching, and
silicon-glass bonding techniques in a cleanroom.
However, filling the cells with the highly volatile
alkali metals and buffer gasses without exposure to
air, and subsequent hermetic sealing of the cells, are
formidable MEMS fabrication problems. The high
temperature required for anodic bonding of silicon
to glass is at odds with the low melting points of
Cs and Rb. Thus, to date, cell fabrication requires
technically complex methods that are limited to se-
quential rather than parallel processes to introduce
the alkali metal into the cell and to subsequently
seal the cell hermetically.

To overcome these disadvantages and simplify the
cell-filling process, we have developed and tested
acesium batch-filling technique based on thin-film
deposition and subsequent decomposition of ce-
sium azide (CsN,). CsN, is a solid atroom tempera-
ture and is stable in air. It decomposes to produce
pure cesium and nitrogen gas when heated to 450
degrees Celsius or through ultraviolet photolysis at

tmm

Unreacted cesium azide

Cesium

Photograph of a Cs MEMS cell as viewed through the
glass window showing in-situ production of Cs.

room temperature. The azide method of cell filling
eliminates the need for pipetting or microfluidic
manipulation of liquid alkali metals since the Cs
is liberated in situ after the cell has been hermeti-
cally sealed, thus simplifying the filling process and
dramatically reducing the tooling cost.

Furthermore, the azide method, being based on
thin-film deposition, is inherently wafer-level.
Due to the lack of thermophysical and thermo-
chemical data on CsN,, as well as the relative lack
of published literature concerning CsN, material
properties, much of this work was exploratory in
nature. While the photolysis of other metal azides
has been studied in detail, the photolysis of CsN,
has not been previously demonstrated or studied
before and as such the mechanisms for the photo-
dissociation are just now coming to light.

mw Chip-Scale Atomic Magnetometer — In
collaboration with the Physics Laboratory, we
have constructed, using MEMS techniques, a
small low-power magnetic sensor based on alkali
atoms. We used a coherent population trapping
resonance to probe the interaction of the atoms’
magnetic moment with a magnetic field, and we
detected changes in the magnetic flux density with
a sensitivity of 50 picotesla per root hertz at 10
hertz. The magnetic sensor has a size of 12 cubic
millimeters and dissipates 195 milliwatts of power.
Further improvements in size, power dissipation,
and magnetic field sensitivity are immediately
foreseeable; such a device could provide a hand-
held battery-operated magnetometer with an atom
shot-noise-limited sensitivity of 0.05 picotesla per
root hertz.

Lock-in Signal (arb. units)

0 10 2 380 40 50
Time (s)

Lock-in amplifier signal plotted as a function of time
as magnetic flux is stepped in 10 second. The magnetic
Flux density during the measurement is nominally 73.9
millitesla.



two quantum states. The proof-of-principle experi-
ment demonstrated a rough agreement between the
new technique and traditional microwave power
measurements.

m Power Standards at Low Frequency — A
new coaxial direct comparison system has been
built to cover the frequency range of 100 kilohertz
to 18 gigahertz. This system extends the lower
range of our direct comparison systems from 50
megahertz down to 100 kilohertz. This new system
gives us much greater efficiency in measuring
power standards. Before, two independent systems
had to be used. There was no significant change in
uncertainties.

m= Software — The Verify and Calkit software
that supports the Agilent 8753 VNA has been
completed and delivered to the U.S. Air Force.
The Air Force will be using this to verify in-house
their inventory of Agilent 8753 verification and
calibration kits at an estimated cost savings of ap-
proximately $100,000 per year.

CaLiBrarTIONS

m= We provide a wide range of state-of-the-art
calibration services for fundamental microwave
quantities, including scattering parameter, power,
thermal noise, and waveform.

=’ Forscattering parameters, we provide calibra-
tions of one- and two-port devices, in a variety of
waveguides and coaxial connector sizes. For coax,
we provide measurements from 10 megahertz to 50
gigahertz. In waveguide, we cover the range from
8.2 to 110 gigahertz and 92 to 96 gigahertz.

m For microwave power, we provide effective
efficiency calibrations of thermistor and thermo-
electric detectors in coax from 100 kilohertz to 50
gigahertz. We provide calibration in waveguide for
thermistor detectors from 8.2 to 75 gigahertz.

= For thermal noise, we provide calibration of
coaxial noise standards at 30 megahertz, 60 mega-
hertz, and from 1.0 to 50 gigahertz, Waveguide
standards are calibrated from 8.2 to 65 gigahertz.

a For waveform, in collaboration with the Op-
toelectronics Division, we provide calibration of
photodetectors and oscilloscopes for microwave
signal characterization. We provide measurements
in coaxial media at frequencies up to 110 gigahertz
and on-wafer up to 200 gigahertz.

SHorT Courses

m We organized the annual Automatic RF Tech-
niques Group (ARFTG)Y/NIST Short Course on
Microwave Measurements in Washington, DC,
in November 2005. The course is a great way to
bring measurement theory and techniques to many
people (attendance is usually around 40) at one
time. During the course we are able to teach the
attendees the latest methods for making the most
accurate microwave measurements. Presentations
were given by Jim Randa on “Thermal Noise
Measurements,” Ron Ginley on “RF Connectors
and Transmission Lines” and “VNA Uncertain-
ties,” and Tom Crowley on “Microwave Power
Measurements.”

m Dave Walker gave lectures at the Asia-Pacific
Microwave Measurements Training Course in
Christchurch, New Zealand, in April 2006, and
in Auckland, New Zealand, in May 2006: “In-
troduction to Microwave Power Measurements,”
“Microwave Power Measurements in Digital
Communications Systems,” and “Thermal Noise
Measurements.”

REcENT PuBLicaTIOoNs

T.P. Crowley, J. Miall, P.M. de Vreede, J. Furrer, A. Michaud,
E. Dressler, T. Zhang, K. Shimaoka, and J. H. Kim, “CCEM
Supplementary Comparison: RF Power Measurements with 2.4
mm Connectors,” CCEM.RF-S1,CL (GTRF/02-03),” Metrolo-
gia (Technical Supplement) 43, 01007 (October 2006).

C. Eig, D. Adamson, J. Randa, D. Allal, and R. Uzdin, “CCEM
Key Comparison: Noise in 50 © Coaxial Line at Frequencies

Tp to-1- GHz,” CCEM-RE-K18:CL (GERF/00-1), Metrologia
(Technical Supplement) 43, 01004 (October 2006).

J. Randa, A. E. Cox, and D. K. Walker, “Proposal for Develop-
ment of a National Microwave Brightness-Temperature Stan-
dard,” Proc. SPIE 6301, 630105 (September 2006).

I.Randa, A. E. Cox, and D. K. Walker, “Proposed Development
ofa National Standard for Microwave Brightness Temperature,”
Int, Geoscience and Remote Sensing Symp. (IGARSS-2006),
Conference Digest, Denver, CO (August 2006).

A.B. Cox and M. D. Janezic, “Preliminary Studies of Electro-
magnetic Properties of Microwave Absorbing Materials used
in Calibration Targets,” Digest Int. Geoscience and Remote
Sensing Symp. (IGARSS-2006), Denver, CO (August 2006).



|— fromFIB.cut.

they interact and phase-lock as in our previous
work. Then we physically cut the magnetic film
between the oscillators with a focused-ion beam
(FIB) nanoscale cutting tool. Cutting the magnetic
film would still allow the two oscillators to see the
magnetic fields produced by each other but would
stop any spin-waves from propagating, just as a
barrier dividing a pool of water stops ripples from
propagating. We found that phase-locking no lon-
ger occurred, showing that the oscillators interact
predominately via spin-waves.

These results set the stage for arranging larger
numbers of nanocontact oscillators into coherent
arrays for use in new types of electronic devices. In
addition, this electrical method provides a new way
to measure spin-waves themselves on length scales
smaller than previously imaginable. This new met-
rological tool may reveal new magnetodynamic
phenomena at nanometer length scales.

‘Bet WO

Electron micrograph of two nanocontacts (dark circles
in light rectangles) with FIB cut between them. Scale
bar is 200 nm. Inset: Micromagnetic simulation show-

|___ing spin-waves emitted by two_contacts,and reflection:

tive switching schemes is the scaling limitations
of conventional MRAM. Spin-torque switching of
MRAM has the advantage that, as the size of the
devices is reduced, the current needed to switch the
free layer orientation is decreased. However, one
difficulty with implementing MRAM nanopillars
in large-scale commercial products is device-to-
device variation of the magnetic properties and the
impact of these variations on the critical switching
current.

To gauge device-to-device variations, we measured
how thermal effects influence the free layer reversal
of spin-valve nanopillars via the spin-torque effect.
We found that room temperature pulsed switching
probability measurements can be used to accurately
predict the critical current for switching at “zero
temperature.” Low temperature measurements of
several different devices provided experimental
values of the critical switching current. Device-to-
device variations in the critical switching current
are drastically reduced at low temperature, with
good agreement between experiment and theory.

I (mA)

Plot of the differential resistance versus current and
magnetic field for an elongated hexagon sample,
50 nanometers by 100 nanometers in size. The nega-

m Influence of Thermal Effects in the Current-
Induced Switching of Magnetic Nanostructures
— The spin-torque effect is an efficient way to
change the orientation of the free layer in multilayer
nanopillars known as a “spin valves.” This effect
has potential applications in commercial MRAM
and has recently been demonstrated as a viable
alternative to the cross-point writing scheme of
conventional MRAM, which is just now coming
to market. One of the reasons for pursuing alterna-

_____tive-going current sweep was subtracted fromthe

positive-going current sweep to highlight hysteretic
regions of the device.

m Detailed Comparison of Spin-Transfer
Precessional Dynamics with Theoretical Pre-
dictions — Since the initial predictions that a
spin polarized current can exert a torque on a
nanoscale magnet, much progress has been made
in understanding the spin-transfer effect and its
manifestations. A number of researchers have
successfully demonstrated both current-induced



Awarp

U.S. Department of Commerce Silver Medal (Bill
Rippard, Stephen Russek, and Tom Silva) and
EEEL Distinguished Associate Award (Matt Pufall
and Shehzaad Kaka) for the discovery of mutual
phase-locking, external frequency-locking, and
frequency modulation of spin-transfer nano-oscil-
lators, 2006.

REcENT PuBLicaTIons

A. McCallum, and S. E. Russek, “Reftaction of Electrons at the
Interfaces in Spin Valves” (submitted for publication).

IM, Shaw, W. H. Rippard, 8. E. Russek, T. Reith, and C. M.
Falco, “Narrow Switching Field Distributions in Perpendicular
Magnetic Nanodot Arrays” (submitted for publication).

W. H. Rippard, M. R. Pufall, and §. E, Russek, “Comparison
of Frequency, Linewidth, and Output Power in Spin Transfer
‘Nanocontact Oscillators” (submitted for publication).

M.L. Schneider, M. R. Pufall, W. H. Rippard, and S. E. Russek,
“Thermal Effects on the Critical Current of Spin Torque Switch-
ing in Nanopillars” (submitted for publication).

B, Cage, S. E. Russek, R. Shoemaker, A. Barker, C. Stoldt, V.
Ramachandarin, and N. Dalal, “The Utility of the Single-Mol-
ecule Magnet Fe, for Magnetic Resonance Imaging Contrast
Agent Over a Broad Range of Concentration,” Polyhedron
(im press).

JM. Shaw and C. M. Falco, “Structure, Spin-Dynemics, and
Magnetic Properties of Annealed Nanoscale Fe Layers on
GaAs,” J. Appl. Phys. (in press).

E. Mirowski, J. Moreland, S. E. Russek, and M. Donahue, “Ma-
nipulation of Magnetic Particles by Patterned Arrays of Mag-
netic Spin-Valve Traps,” J. Magn. Magn. Mater. (in press).

I. M. Shaw, R. Geiss, and S. E. Russek, “Dynamic Lorentz
Microscopy of Micromagnetic Structure in Magnetic Tunnel
Junctions” Appl. Phys. Lett, 89, 212503 (November 2006).

P. Voskoboynik, R. D. Joos, W. E. Doherty, and R. B. Goldfarb,
“Low Magnetic Moment PIN Diodes for High Field MRI Sur-
face Coils,” Medical Phys. 33, 4499-4501 (December 2006).

M. R. Pufall, W. H. Rippard, S. E. Russek, S. Kaka, and J. A.
Katine, “Electrical Measurement of Spin-Wave Interactions of
Proximate Spin Transfer Nanooscillators,” Phys. Rev. Lett. 97,

A. J. Barker, B. Cage, S. E. Russek, R. Garg, R. Shandas,
and C. R. Stoldt, “Tailored Nanoscale Contrast Agents for
Magnetic Resonance Imaging,” Proc. ASME International
Mechanical Engineering Congress and Exposition, Orlando,
FL (November 2005).

S. Kaka, M. R. Pufall, W. H. Rippard, T. J. Silva, S. E. Russek,
and J. A. Katine, Mutual Phase-Locking of Microwave Spin
Torque Nano-Oscillators, Nature 437, 389-392 (September
2005).

B. Cage, 8. B. Russek, D. Zipse, J.M. North, andN. S. Dalal,
“Resonant Microwave Power Absorption and Relaxation of
the Energy Levels of the Molecular Nanomagnet Fe8 Using
Superconducting Quantum Interference Device-Based Magne-
tometry,” Appl. Phys, Lett, 87, 082501 (August 2005).

W.E. Bailey, S. E. Russek, X.-G. Zhang, and W. H. Butler, “Ex-
perimental Separability of Channeling Giant Maguetoresistance
in Co/Cu/Co,” Phys. Rev. B 72, 012409 (July 2005).

B, Mirowski, J. Moreland, A. Zhang, S. E. Russek, and M. J.
Donahue, “Manipulation and Sorting of Magnetic Particles by
a Magnetic Force Microscope on a Microfluidic Magnetic Trap
Platform,” Appl. Phys. Lett. 86, 243901 (June 2005).

B, Cage, S. E. Russek, D. Zipse, andN, S. Dalal, “Advantages of
Superconducting Quantum Interference Device-Detected Mag-
netic Resonance Over Conventional High-Frequency Electron
Paramagnetic Resonance for Characterization of Nanomagnetic
Materials,” J. Appl. Phys. 97, 10M507 (May 2005).

N. A. Stutzke, $. E. Russek, D. P. Pappas, and M. Tondra,
“Low-Frequency Noise Measurements on Commercial Magne-
toresistive Magnetic Field Sensors,” J. Appl. Phys. 97, 10Q107
(May 2005).

W. L. Johnson, S. A. Kim, S. E. Russek, and P. Kabos, “Bril-
louin Light Scattering from Pumped Uniform-Precession and
Low-k Magnons in Ni,,Fe,,” Appl. Phys. Lett. 86, 102507
(March 2005).

S. E. Russek, 8. Kaka, W. H. Rippard, M. R. Pufall, and T. J.
Silva, “Finite-Temperature Modeling of Nanoscale Spin-Trans-
fer Oscillators,” Phys. Rev. B 71, 104425 (March 2005).

M. R. Pufall, W. H. Rippard, §. Kaka, T. J. Silva, and S. E.
Russek, “Frequency Modulation of Spin-Transfer Oscillators,”
Appl. Phys. Lett. 86, 082506 (February 2005).

D. Min, A. McCallum, $, E, Russek, and J. Moreland, “Mi-
cromechanical Torque Magnetometer with Sub-Monolayer
Sensitivity,” J. Magn. Magn. Mater. 286, 329-335 (February
2005).

S. Kaka, M. R. Pufall, W. H. Rippard, T. J. Silva, S. E. Russek,
J.A. Katine, and M. Carey, “Spin Transfer Switching of Spin
Valve Nanopillars Using Nanosecond Pulsed Currents,” J.
Magn. Magn. Mater, 286, 375-380 (February 2005).

B. Cage and S. Russek, “Design for a Multifrequency High
Magnetic Field Superconducting Quantum Interference De-
vice-Detected Quantitative Electron Paramagnetic Resonance
Probe: Spin-Lattice Relaxation of Cupric Sulfate Pentahydrate
(CuSO -5H,0),” Rev, Sci. Instrum. 78, 4401-4405 (Noveraber
2004).

087206 (August 2006), WB Ripa, M.-R_-Pofall, S. Kaka, TI. Silva, and S-E.

Russek, “Current-Driven Microwave Dynamics in Magnetic
Point Contacts as a Function of Applied Field Angle,” Phys.
Rev. B70, 100406 (September 2004).

A. T. McCallum and S. B. Russek, “In Site Observation of
Nano-Oxide Formation in Magnetic Thin Films,” JEEE Trans.
Magn. 40, 2239-2241 (July 2004).

M.R. Pufall, W. H. Rippard, 8. Kaka, S. E. Russek, T. J. Silva,
I. Katine, and M. Carey, “Large-Angle, Gigahertz-Rate Random
Telegraph Switching Induced by Spin-Momentum Transfer,”
Phys. Rev. B 69, 214409 (Sune 2004).



:

Micro/Nano ELecTRONICcS

Goa.s

The next generation of high-frequency electromag-
netic applications will require higher operating
frequencies, wider bandwidths, increased dynamic
range, and a substantial reduction in device dimen-
sions. To meet these challenges, the Micro/Nano
Electronics Project develops new measurement
techniques, standards, and instrumentation to sat-
isfy the growing metrology needs of the high-speed
telecommunications, microelectronics, magnetic
storage, and computing industries.

Customer NEEps

The full impact of nanotechnology research may
be decades away, but one current critical need,
according to the National Nanotechnology Initia-
tive (NND), is the creation and development of the
fundamental metrology necessary to characterize
nanoscale electrical and magnetic devices. An ad-
ditional complexity is that future applications of
both microwave and nanotechnology will involve
the transmission and detection of broad-bandwidth
signals having complicated modulation schemes
at frequencies ranging from the microwave region
to the terahertz region. Therefore, development of
nanotechnology metrology will require synergy
between research areas as diverse as nanoelectron-
ics, telecommunications, microwave metrology,
and materials science.

TECHNICAL STRATEGY

To support the future needs of the microelectronics
and emerging nanoelectronics industries, both the
International Technology Roadmap for Semicon-
ductors (ITRS) and the NNI outline many of the
metrology needs that must be addressed for the next
generation of microelectronic and nanoelectronic
devices. In both of these-industries, metrology
must be developed for characterization of smaller
devices that carry complicated, modulated sig-

expertise, we are extending traditional on-wafer
techniques to develop the necessary metrology for
supporting the telecommunications and emerging
nanoelectronics industry. One such extension is
in the area of high-speed waveform metrology.
As data rates of optical links exceed 40 gigabits
per second, and emerging digital circuits operate
with clock rates over 100 gigahertz, electrical
measurements with conventional techniques no
longer work; they are invasive and limited in fre-
quency. To meet this need, we have developed a
fully calibrated electro-optic sampling system for
characterizing photodetectors and calibrating os-
cilloscopes for microwave signal characterization.
This has enabled us to develop new tools, such as
electro-optic on-wafer scattering and waveform
measurements up to 200 gigahertz and modulated
microwave signal and coaxial signal-source char-
acterization to 400 gigahertz. With these tools, we
are providing the fundamental metrology that will
enable development of the next generation of high-
frequency oscilloscopes, microwave transition
analyzers (MTAs), and related instruments.

High-frequency characterization of nanodevices
is another focus of research in this project. De-
velopment of atomic force microscopes (AFMs),
scanning tunneling microscopes (STMs), and
high-impedance and near-field evanescent probing
systems that operate at high frequencies allows
for characterization of the electromagnetic fields,
materials, and nanodevice electrical properties at
frequencies in the microwave and millimeter-wave
range with submicrometer resolution.

Another extension of the on-wafer microwave
metrology work is in the area of on-wafer noise
characterization. Here, we are developing new
measurement techniques that can be used to char-
acterize the on-wafer noise properties of comple-
mentary metal oxide semiconductor (CMOS)
devices, which can be used not only to improve

Technical Contacts:
Mike Janezic

Pavel Kabos

Jim Randa

Kate Remley

Dylan Williams

Staff-Years (FY 2006):
3.0 professionals
0.7 technician

nals at frequencies that extend into and beyond
the microwave range. This project’s expertise in
microwave and terahertz metrology, high-speed
waveform metrology, measurements for telecom-
munication systems, and high-frequency nanode-
vice characterization allows it to tackle some of the
major metrology issues facing the microelectronics
and nanoelectronics industries.

This project has played an important role in de-
veloping the fundamental tools for performing on-
wafer microwave measurements. Building on this

device performance but to assist in physical model
development. In addition to the measurements
performed on-wafer, we are also developing new
techniques for noise characterization at terahertz
frequencies, which will provide traceability to a
critical parameter of active terahertz devices.

In addition to the on-wafer activities, the proj-
ect also develops measurement methods and
calibrations for coaxial instrumentation capable
of accurately characterizing RF-based systems that
transmit complex modulated signals. These include



ELECTRONICS AND ELECTRICAL
ENGINEERING LABORATORY

ELECTROMAGNETICS
DIVISION

Procrams, AcTIVITIES, AND
ACCOMPLISHMENTS

NISTIR 7371

January 2007

U.S. DEPARTMENT OF COMMERCE

~“Carlos M. Gutierrez, Secretary

Technology Administration
Robert Cresanti, Under Secretary of Commerce for Technology

National Institute of Standards and Technology
William Jeffrey, Director



Division staff members perform field penetration tests
on a NASA space orbiter.

AccomPLISHMENTS

m Aircraft Shielding — We have developed
a unique, leading-edge portable measurement
system for the evaluation of coupling to complex
aircraft environments. The system has been used
to evaluate a number of flight vehicles such as the
NASA Orbiter Endeavour, a U.S. Air Force early-
warning aircraft, and a Boeing 767 commercial
aircraft. Evaluations of a Boeing 737-200 and a
Bombardier Global 5000 aircraft at the Federal
Aviation Administration (FAA) Technical Center in
Atlantic City, New Jersey, were recently performed.
The data from this effort are in the public domain.
and have been disseminated to the aircraft testing
community.

= Complex Cavity Modeling — Numerical
models of complex cavities have been developed
to facilitate understanding of measurements per-
formed in aircraft environments. This work is
sponsored by the FAA,

m Building Materials Characterized —A free-
field materials measurement system for the evalua-
tion of building materials has been developed.

= EMC Facilities Tested — Several EMC fa-
cilities have been tested. A measurement effort was
conducted recently at a wastewater instrumentation
company to assess the effectiveness of an anechoic
chamber retrofit. Significant improvements in
chamber performance were realized through a
NIST portable measurement system.

REeceENT PusBLicaTions

R, Johnk, D. Novotny, C. Grosvenor, and N. Canales, “An
Electric-Field Uniformity Study of an Outdoor Vehicular Test
Range,” IEEE Int, Symp. Electromagnetic Compatibility,
Portland, OR (August 2006).

R.T. Johnk, D. R. Novotny, C. A. Grosvenor, N. Canales, and
1.G. Veneman, “Time-Domain Measurements of Radiated and
Conducted Ultrawideband Emissions,” IEEE Aerospace and
Electronic Systems Mag., 19, 18-22 (August 2004).

D, Novotny, C. Grosvenor, R. Johnk, and N. Canales, “Pan-
oramic, Ultrawideband, Diagnostic Imaging of Test Volumes,”
Proc, 2004 IEEE int. Symp. Electromagnetic Compatibility,
Santa Clara, CA, pp. 25-28 (August 2004).

C. Grosvenor, R. Johnk, D. Novotny, and N. Canales, “TEM
Horn Antennas: A Promising New Technology For Compliance
Testing,” Proc. 2004 IEEE Int, Symp. Electromagnetic Compat-
ibility, Santa Clara, CA, pp. 913-918 (August 2004).



most” made in the far field; and (5) extensions of near-field antenna theory to other applications such
as acoustics, field synthesis, and the evaluation of far-field (compact range) measurement systems. We
welcome proposals on these and other topics that extend or improve the application of spherical near-
field measurement techniques.

ELECTROMAGNETIC THEORY FOR Time-Domain ANALYSIS
R.T. Johnk

The transient behavior of both canonical and complex objects subjected to an electromagnetic (EM) im-
pulse from a radiating source is studied. Although transient problems can be analyzed by inverse Fourier
transformation of frequency-domain data, the time-domain technique has several advantages over the
frequency-domain technique. The broadband nature of time-domain analysis facilitates the understand-
ing of nonlinearities, and the ability to model propagation delays provides improved physical insights
related to the spatial geometry of the problem. Problems of both radiation and scattering from complex
structures with both linear and nonlinear loadings are appropriate topics for study. The theoretical and
experimental results will be applied to canonical problems to provide useful physical insights into the
interaction of EM waves with devices and materials.

ELECTROMAGNETIC THEORY FOR ComPLex ENVIRONMENTS
P. F. Wilson and D. A. Hill

Most electromagnetic field measurements seek to create a simple, well defined environment. However,
real electromagnetic environments are typically complex and poorly defined. Multiple sources and
scattering objects (possibly unknown or nonstationary), complicated geometries, proximity coupling,
and other real world complications make electromagnetic field measurements difficult to interpret. Sta-
tistical electromagnetic approaches are needed to quantify both real environments and complex system
responses. This need already exists for large systems (e.g., avionics, interconnected electronics) and the
requirement will move to the component level as frequencies of operation continue to move higher (e.g.,
high-speed computers, digital wireless systems). Research opportunities exist for developing statistical
electromagnetic models. Applications include reverberation chamber test methods, coupling to complex
systems, shielding of ill defined geometries, radiation from statistically defined sources, propagation in
nonstationary environments, and characterization of complex electromagnetic environments. The goal
is to develop analytical descriptions for the statistics of these environments. Numerical modeling and
Monte Carlo techniques will be used to verify analytical models. Excellent experimental facilities exist
to generate measured data for comparison with theoretical and simulation results.

ANTENNA THEORY AND Measurements I
R. C. Wittmann and M. H. Francis

A “scattering matrix description of antennas and antenna-antenna interactions” has been developed and
successfully applied by researchers in this division. Radiated fields are determined from measurements
made in the near field of the antenna under test, and the theory is suitable for describing antenna inter-
actions at arbitrary distances (not just in the far-field region). Measurement techniques (and supporting
theory) must continuously be extended to keep pace with the rapid advancement in antenna design and
application. Topics that need attention include (1) better accuracy — high performance systems, especially
those that are satellite based, require maintenance of tighter tolerances; (2) higher frequencies — more
sophisticated near-field measurement methods are needed to handle millimeter-wave applications (up
to above 500 gigahertz); (3) complex phased-array antennas — large, often electronically steerable,
phased arrays need special diagnostic tests to ensure optimum functionality; (4) low sidelobe antennas
— military and commercial communication applications increasingly specify sidelobe levels 50 dB or
more below peak, a range where measurement by standard technique is difficult; (5) in situ (or remote)
evaluation — many systems cannot be transported easily to a measurement laboratory; robust methods
are needed for on-site testing; and (6) multiple reflections — methods are needed to mitigate errors
caused by multiple reflections between the probe and test antenna. Research facilities include two planar
near-field scanners, a multipurpose range for cylindrical and spherical antenna measurements, a preci-



Technical Contact:
Mike Francis

Staff-Years (FY 2006):
2.0 professionals
1.0 research associate

ANTENNAS AND ANTENNA SysTEMs:
ANTENNA THEORY AND APPLICATIONS

Goats

The Antenna Theory and Applications Project devel-
ops, refines, and extends measurement techniques to
tneet current requirements and to anticipate future
needs for accurate antenna characterization.

Customer NEEDs

Microwave antenna hardware continues to become
more sophisticated. We provide state-of-the-art
measurement support for antennas and antenna
systems. Customer needs include:

Improved Accuracy — High-performance sys-
tems, especially those that are satellite-based,
require maintenance of tighter tolerances.

Higher Frequencies — Millimeter-wave applica-
tions up to 500 gigahertz are being developed.

Low-Sidelobe Antennas — Military and com-
mercial communications applications increasingly
require sidelobe levels of 50 decibels below peak
(or better), a range where measurement by standard
techniques is difficult.

Complex Phased-Array Antennas — Large, often
electronically steerable, phased arrays require spe-
cial diagnostic tests to ensure full functionality.

In Situ and Remote Measurements — Many
systems cannot be transported to a measurement
laboratory. Robust techniques are needed for on-
site testing.

Production-Line Evaluation — Techniques are
required that emphasize speed and economy, pos-
sibly at the expense of the ultimate accuracy.

RFID Reliability — RF identification (RFID) is
being used in new applications such as inventory
control and electronic passports. Test methods are
needed to assure reliability and security.

Evaluation of Anechoic Chambers and Compact
Ranges — A number of widely used measurement
systems rely on establishing a well characterized
test field. Near-field methods can be used to evalu-
ate and analyze the quality of these test fields.

TECHNICAL STRATEGY

We seek to expand our frequency coverage for
antenna calibrations to meet the demands of gov-
ernment and industry. A probe-position correction

theory has been developed. Probe-position cor-
rection has been implemented at the NIST range
by using a laser tracker to dynamically acquire
position data. This will help us maintain low un-
certainties as we extend the frequency coverage of
our calibrations.

The near-field extrapolation method, developed at
NIST, is an accurate technique to characterize the
on-axis gain and polarization properties of anten-
nas. Further improvement is still possible. We plan
to extend the extrapolation software to take full
advantage of phase information and to analyze the
conditioning of the algorithm.

A thorough uncertainty analysis for planar near-
field measurements has been previously developed.
A similarly comprehensive uncertainty analysis is
needed for spherical near-field measurements. We
have completed a preliminary analysis and are
working to refine the bounds.

In-situ near-field measurements of antenna systems
are problematic because of the mechanical difficul-
ties in maintaining position tolerances and because
full spherical scans are typically not physically
feasible. We have made significant progress in
overcoming both these challenges and are working
on the practical implementation of a deployable
measurement system.

AccomPLISHMENTS

= Proximity Effects in Microwave Radiom-
eter Calibrations — Microwave radiometers are
calibrated by observing sources of known bright-
ness temperature, assuming the source is in the
far field. However, such sources are often actually
in the near field. A simulation for estimating the
uncertainty due to the source being in the near
field of the radiometer has been completed and
documented.

= Comparison of Gains Determined from the
Extrapolation and Pattern Integration Methods
— The gains of three antennas (one a dual-port
probe) were determined with both the extrapola-
tion and pattern integration methods and the results
compared. For antennas with gains greater than
about 15 decibels, the uncertainties of the two
methods were comparable. For gains less than 15
decibels, the extrapolation method was found to be
superior in the NIST facility.



THe ELectronics anp ELECTRICAL
ENGINEERING LasoraTory

One of NIST’s seven Measurement and Standards Laboratories,
EEEL conducts research, provides measurement services, and
helps set standards in support of: the fundamental electronic
technologies of semiconductors, magnetics, and superconduc-
tors; information and communications technologies, such as
fiber optics, photonics, microwaves, electronic displays, and
electronics manufacturing supply chain collaboration; foren-
sics and security measurement instrumentation; fundamental
and practical physical standards and measurement services for
electrical quantities; maintaining the quality and integrity of
electrical power systems; and the development of nanoscale and
microelectromechanical devices. EEEL provides support to law
enforcement, corrections, and criminal justice agencies, includ-
ing homeland security.

EEEL consists of four programmatic divisions and two matrix-
managed offices:

Semiconductor Electronics Division
Optoelectronics Division

Quantum Electrical Metrology Division
Electromagnetics Division

Office of Microelectronics Programs

Office of Law Enforcement Standards

This document describes the technical programs of the

Electromagnetics Division. Similar documents describing the

other Divisions and Offices are available. Contact NIST/

EEEL, 100 Bureau Drive, MS 8100, Gaithersburg, MD ;
20899-8100, telephone: (301) 975-2220, on the Web:

http://www.eeel.nist.gov

On the cover (clockwise from upper left): extrapolation range for antenna measurements covering
50 to 110 gigahertz, portable system for measuring shielding of aircraft, vacuum chip bonder for
making chip-scale alkali vapor cells, permittivity of fluids and foams, terahertz imaging system,
spin-transfer oscillator measurements.



m IEC 61788-13 Superconductivity — Part 13:
AC Loss Measurements — Magnetometer Methods
for Hysteresis Loss in Cu/Nb-Ti Multifilamentary
Composites

m IEC 60050-815 International Electrotechnical
Vocabulary — Part 815: Superconductivity

REcENT PuBLicATIONS

L. F, Goodrich and J. D. Splett, “Current Ripple Effect on n-
Value” (submitted for publication).

L. F. Goodrich, N. Cheggour, J. W. Ekin, and T. C. Stauffer,
“Critical-Current Measurements on ITER Nb,Sn Strands: Effect
of Temperature” (submitted for publication).

N. Cheggour, J. W. Ekin, and L. F. Goodrich, “Critical-Current
Measurements on ITER Nb, Sn Strands: Effect of Axial Tensile
Strain” (submitted for publication).

L.F. Goodrich, “Voltage Versus Magnetic Field Measurements
on Nb,Sn Wires,” Ads. Cryo. Eng. (Materials) 52B, 520-527
(2006).

L.F. Goodrich and T. C. Stauffer, “Variable-Temperature Criti-
cal-Current Measurements on a Nb,Sn Wire,” IEEE Trans. Appl.

Supercond. 15, 3356-3359 (June 2005).

L. F, Goodrich, T. C. Stauffer, J. D. Splett, and D. F. Vecchia,
“Unexpected Effect of Field Angle in Magnetoresistance Mea-
surements of High-Purity Nb,” IEEE Trans. Appl. Supercond.
15, 3616-3619 (June 2005).

N.N. Martovetsky, P. Bruzzone, B. Stepanov, R. Wesche, C.-
Y. Gung, J. V. Minervini, M. Takayasu, L. F, Goodrich, J. W.
Ekin, and A. Nijhuis, “Effect of Conduit Material on CWX
Performance Under High Cycling Loads,” JEEE Trans. Appl.
Supercond. 15, 1367-1370 (Tune 2005).

L. F. Goodrich, T. C. Stauffer, J. D. Splett, and D. F. Vecchia,
“Measuring Residual Resistivity Ratio of High-Purity Nb,” Adv
Cryo. Eng. (Materials) 50, 41-48 (Tuly 2004).

L. F. Goodrich and T. C. Stauffer, “Variable-Temperature Criti-
cal-Current Measurements on a Nb-Ti Wire,” Adv. Cryo. Eng.
(Materials) 50, 338-345 (July 2004).



Technical Contact:
Galen Koepke

Staff-Years (FY 2006):
3.0 professionals
2.2 research associates

ELECTROMAGNETIC CompParIBILITY:
Compcex FieE_ps

Goats

The Complex Fields Project develops and maintains
measurement methods to quantify fields in complex
environments, such as electrically large cavities
and highly nonuniform boundaries. Applications
include the reverberation chamber, the statistics
of electromagnetic fields in rooms and buildings,
the communications needs of first responders
to emergencies, measurements of shielding ef-
fectiveness of advanced composites, coupling to
large-scale systems and components, coupling to
biological objects, advanced numerical methods,
and metamaterials. These efforts support industry
and government agencies, national and interna-
tional standards, health care, homeland security,
and nanotechnology.

Customer Neeps

Large, complex systems located in complex field
environments need to be tested for electromagnetic
compatibility (EMC). Electromagnetic interfer-
ence (EMI) affects U.S. competitiveness (through
trade restrictions and regulations), national se-
curity, health, and safety. EMC regulations and
requirements constitute 1 to 10 percent of the total
U.S. product costs and can cause delays to market,
We are providing research and support to address
a number of critical areas:

Reverberation Chambers — Reverberation
chambers are used to test large complex systems
at high frequencies. Users of reverberation cham-
bers need better models of statistical parameters,
improved chamber and stirrer designs, test object
models, and guidance for incorporating reverbera-
tion chamber technology into national and inter-
national standards.

Shielding of Advanced Composites — Shield-
ing effectiveness of advanced composites cannot
be readily tested with existing methods, such as
the American Society for Testing and Materials
(ASTM) coaxial fixture. New methods are needed,
such as the use of nested reverberation chambers.

Coupling to Biological Objects — The increased
use of wireless devices in scattering-rich environ-
ments is creating questions about the effects of
such electromagnetic field exposure on humans and
animals. These conditions need to be replicated in
controlled experiments,

First Responder Communications — First
responders to emergency situations encounter dif-
ficult communications scenarios. There is a need to
better understand propagation in a wide variety of
environments, including collapsed buildings.

Complex Boundaries — The electromagnetic
interface between complex media is a difficult
modeling and measurement problem. Advances at
both the macro- and micro-scale are needed.

TECHNICAL STRATEGY

Our goal is to develop and evaluate reliable and
cost-effective standards, test methods, and mea-
surement services related to complex electromag-
netic fields for EMC of electronic devices and
other applications in health, defense, and homeland
security, This includes investigating new applica-
tions for existing test facilities as well as improving
methods for evaluating the critical characteristics
of support hardware, such as antennas, cables, con-
nectors, enclosures, and absorbing material.

Reverberation chambers are increasingly a key
tool for EMC testing in the gigahertz frequency
range. The recent publication of IEC61000-4-21 on
reverberation chamber test methods will increase
usage. We have played a leading role in developing
reverberation chamber technology. We continue to
develop models for the statistical behavior of the
fields in the test volume and near the boundaries,
While the typical target for a reverberation chamber
is a Rayleigh field distribution, multiple-input/
multiple-output (MIMO) system testing requires
a Rician field distribution. We will investigate
methods to accurately control the ratio between
direct and indirect coupling for MIMO and other
test applications. Probes are traditionally calibrated
in highly controlled reference fields. We will inves-
tigate whether the large volume of a reverberation
chamber can be used to simultaneously calibrate
a large number of field probes. We are developing
analytical models of test-object directivity. We will
continue to experimentally test these models and
transfer results to committees developing standards
for reverberation chambers.

Advanced composites offer weight and performance
advantages over metals and are increasingly being
used in aerospace and other applications. Plastics
inherently provide no significant shielding to elec-
tromagnetic fields. Plastics can be “metalized” by



Book

Jack Ekin’s new textbook, Experimental Tech-
niques for Low-Temperature Measurements, was
published by Oxford University Press in October
2006. The text covers the design of cryogenic
measurement probes, and the appendix provides
cryogenic materials data for carrying out that de-
sign. The textbook is written for beginning gradu-
ate students, industry measurement engineers, and
materials scientists interested in learning how to
design successful low-temperature measurement
systems. Topics include heat-transfer techniques
for designing a cryogenic apparatus, selecting
materials appropriate for such apparatus, how to
make high-quality electrical contacts to a supercon-
ductor, and techniques for reliable critical-current
measurements,

The appendix is a data handbook of materials
properties and cryostat design consisting of 70
tables compiled from over 50 years of literature.
The tables were compiled for experts in the field
of cryogenic measurements and include electrical,
thermal, magnetic, and mechanical properties of
materials for cryostat construction; properties of
cryogenic liquids; and temperature measurement
tables and thermometer properties.

XPERIMENTAL
TECHNIQUES
LOW-TEMPERATURE
MEASUREMENTS

Cover of new book on cryogenic measurement tech-
niques.

Award

Superconductivity for Electric Systems Program,
Office of Electricity Delivery and Energy Reliabil-
ity, U.S. Department of Energy, recognition as top
ranked project, 2005 and 2006 (Jack Ekin, Najib
Cheggour, and Danko van der Laan).

REcENT PUBLICATIONS

D. C.-van der Laan and J. W. Ekin, “Large Intrinsic Bffect
of Axial Strain on the Critical Current of High-Temperature
Superconductors for Electric Power Applications” (submitted
for publication).

N. Cheggour, J. W. Ekin, C. L. H. Thieme, and Y.-Y. Xie, “Ef
fect of Fatigue Under Transverse Compressive Stress in Slitted
Y-Ba-Cu-O Coated Conductors” (submitted for publication).

N. Cheggour, J. W. Ekin, and L. F. Goodrich, “Critical-Current
Measurements on ITER Nb,Sn Strands: Effect of Axial Tensile
Strain” (submitted for publication).

L. F. Goodrich, N. Cheggour, J. W. Ekin, and T. C. Stauffer,
“Critical-Current Measurements on ITER Nb,Sn Strands: Effect
of Temperature” (submitted for publication).

I. W. Ekin, Experimental Techniques for Low-Temperature
Measurements — Cryostat Design, Material Properties and
‘Superconductor Critical-Current Testing, Oxford Univ. Press,
UK. (October 2006).

C.C. Clickner, J. W. Ekin, N. Cheggour, C. L. H. Thieme, Y.
Qiao, ¥.-Y. Xie, and A. Goyal. “Mechanical Properties of Pure
Ni and Ni-Alloy Substrate Materials for Y Ba Cu O Coated
Conductors,” Cryogenics 46, 432-438 (June 2006).

D.C. van der Laan, J. W. Ekin, H. J.N. van Eck, M. Dhalle,
B, ten Haken, M. W. Davidson, and J. Schwartz, “Effect of
Tensile Strain on Grain Connectivity and Flux Pinning in
BiSr,Ca,Cu,O, Tapes,” Appl. Phys. Lett. 88, 022511 (Janu-
ary 2006).

N. Cheggour, J. W. Ekin, C. L. H. Thieme, Y.-Y. Xie, V. Sel-
vamanickam, and R. Feenstra. “Reversible Axial-Strain Effect
in Y Ba-Cu-O Coated Conductors,” Supercond. Sci. Technol.
18, $319-S324 (December 2005).

N. Cheggour, J. W. Ekin, Y.-Y. Xie, V, Selvamanickam, C. L.
H. Thieme, and D. T. Verebelyi, “Enhancement of the Irre-
versible Axial-Strain Limit of Y Ba-Cu-O Coated Conductors
with the Addition of a Cu Layer,” Appl. Phys. Lett. 87, 212505
(November 2005).

Y.-Y. Xie, A. Knoll, Y. Chen, Y. Li, X. Xiong, Y. Qiao, P. Hou,
|__I. Reeves, T. Salagaj, K. Lenseth, L, Civale, B. Maiorov, Y.

Iwasa, V. Solovyov, M. Suenaga, N. Cheggout, C. Clickner, J.
W. Ekin, C. Weber, and V. Selvamanickam. “Progress in Scale-
Up of Second-Generation High-Temperature Superconductors
at Superpower,” Physica C 426, 849-857 (October 2005).

N. Cheggour, J. W. Ekin, and C. L. H. Thieme, “Magnetic-Field
Dependence of the Reversible Axial-Strain Effect in Y-Be-Cu-O
Coated Conductors,” JEEE Trans. Appl. Supercond. 15, 3577-
3580 (June 2005).



— WR-22 — 2 standard gain horns and 2
dual-port circularly polarized probes

— WR-62— Cassegrain dish antenna

= A60to 110 gigahertz extrapolation range has
been designed and installed. Antenna gain tests at
94 gigahertz show excellent performance. The new
range significantly extends NIST antenna metrol-

ogy capability.

REcENT PuBLIcATIONS

J. R. Guerrieri, M. H. Franeis, P. F. Wilson, A. B. Kos, L.
E. Miller, N. P, Bryner, D. W. Stroup, and L. Klein-Berndt,
“RFID-Assisted Indoor Localization and Communication for
First Responders,” Proc. Antenna Measurement Techniques
Association (AMTA), Austin, TX (October 2006); Proc. Euro-
pean Conference on Antennas and Propagation, Nice, France
(November 2006).

K. MacReynolds, J. Guerrieri, and D. Tamura, “Three-Antenna
Extrapolation Gain Measurement System at Millimeter Wave
Frequencies,” Proc. Antenna Meas. Tech. Assoc. (AMTA),
Austin, TX (October 2006).

L.E. Miller, P. F. Wilson, N. P, Bryner, M. H. Franeis, J. R.
Guerrieri, D. W. Stroup, and L. Klein-Berndt, “RFID-Assisted
Indoor Localization and Communication for First Responders,”
Proc. 2006 Intl. Symp. Advanced Radio Tech. (ISART), Boulder,
CO, pp. 83-91 (March 2006).

J. Guerrieri, K. MacReynolds, M. Francis, R. Wittmann, and D.
‘Tamura, “Planar Near-Field Measurement Results at 94 GHz
Using Probe Position Correction,” Proc. Antenna Meas. Tech.
Assoc. (AMTA), Atlanta, GA, pp. 356-359 (October 2005).

M. Francis, K. MacReynolds, and J. Guetrieri, “Comparison of
Gains Determined from the Extrapolation and Pattern Integra-
tion Methods,” Proc. Antenna Meas. Tech, Assoc. (AMTA),
Atlanta, GA, pp. 356-359 (October 2005).

J. Guerrieri, K. MacReynolds, M. Francis, R. Wittmann, and
D. Tamura, “Practical Implementation of Probe-Position Cor-
rection in Planar Near-Field Measurements,” Proc. Antenna
Meas. Tech. Assoc. (AMTA), Atlanta, GA, pp. 356-359 (Oc-
tober 2004).

J. Randa, A. Cox, D. Walker, M. Francis, J. Guerrieri, and K.
MacReynolds, “Standard Radiometers and Targets for Micro-
wave Remote Sensing,” Int. Geoscience and Remote Sensing
Symp. (IGARSS), Anchorage, AK (September 2004).

J. Guerrieri, K. MacReynolds, and D. Tamura, “Evaluation of
a Radiometer Phase Retardation Plate Using Planar Near-Field
Measurements,” Proc. National URSI Meeting, Boulder, CO
(January 2004).

J. Guerrieri, K. MacReynolds, and D. Tamura, “Radiometer
Phase Retardation Plate Evaluation Using Planar Near-Field
‘Antenna Measurements,” Proc. Antenna Meas. Tech. Assoc.
(AMTA), Irvine, CA (October 2003).



ments in industry. In conjunction with our on-wafer
noise efforts (see the Micro/Nano Electronics Proj-
ect), we are working to improve on-wafer measure-
ment methods for noise parameters of transistors,
and we will also develop methods of supporting
those measurements in industry.

New microwave remote-sensing radiometers are
designed for unprecedented accuracy. In order to
verify (and possibly to even achieve) that accuracy,
astable, accurate reference standard is required. We
have proposed development of national standards
for microwave brightness temperature in frequency
bands of interest. The standards would be traceable
to the NIST primary noise standards. We are also
working on methods to characterize calibration
targets commonly used in microwave radiometry.
Additionally we are automating our noise tempera-
ture systems to greatly increase their efficiency.

Power

For a number of years, power measurements above
50 gigahertz were based on calorimetric. and six-.
portreflectometer measurements using rectangular
waveguides. NIST’s internal power standards were
characterized in the calorimeters and the measure-
ments transferred to customer devices by use of the
six-port systems. The NIST primary transfer stan-
dards were modified commercial power sensors,
and the calorimeters weré:designed specifically for
these standards. Measurement services were avail-
able in 1 gigahertz steps from 50 to 75 gigahertz
and from 92 to 96 gigahertz.

Improvements in .our standards are needed for
a number of reasons. Frequency coverage in
1 gigahertz steps is not adequate for characterizing
broadband digital devices such as optoelectronics
components that operate at 40 gigabits per second.
There is increasing use of frequencies above 75
gigahertz that were not previously measured. The
modified commercial power sensors that NIST
used as transfer standards are no longer reliable
and cannot be replaced.

evaluate a customer device at about 50 frequencies
per day has been developed for WR-15 (50 to 75
gigahertz) and is being used for customer calibra-
tions. A direct comparison system for WR-10 (75
to 110 gigahertz) has been constructed but not yet
evaluated. New calorimeters are being designed
for both WR-10 and WR-15. They will accom-
modate a wider variety of internal standards than
the present calorimeters. Future plans include the
extension of the direct comparison measurements
to 1.85 millimeter coaxial connectors that will al-
low measurements from DC to 65 gigahertz with
a single connector. These measurements will be
traceable to the WR-15 and 2.4 millimeter calori-
metric primary standards.

RF power measurements have traditionally been
traceable to DC power measurements through
RF/DC substitution techniques. An alternative
approach is to measure the field strength of mi-
crowaves through their effect on the quantum
state of atoms. In this measurement, a group of
atoms is created in a single quantum state. They
are then exposed to microwaves at a frequency that
corresponds to the energy difference between this
state and a second quantum state. The atoms will
oscillate between the two states at a frequency that
is proportional to the field strength. This process
is known as a Rabi oscillation. By measuring the
number of atoms in each state, the field strength
can be determined. A proof-of-concept experiment
was conducted in collaboration with the Physics
Laboratory. The next stage in this work will be an
experiment that accurately compares a traditional
measurement with the quantum measurement.

In order to address these problems, new calo-
timeters are being developéd so that a wider set
of transfer standards can be used. Faster transfer
measurements are being developed so that denser
frequency coverage can be readily obtained.
We have obtained a new synthesizer (up to 67
gigahertz) and a backward-wave oscillator (50
to 110 gigahertz) source t ave replaced the —

manually tuned Gunn diode oscillators for most
measurements. A direct comparison system thatcan power system.

Calibration measurements on the direct comparison



Ce

Microsystems FoR Bio-lMAGING AND METROLOGY

Goats

The Microsystems for Bio-Imaging and Metrol-
ogy Project designs, fabricates, and tests micro-
electromechanical systems (MEMS) for studying
microscopic and nanoscopic magnetic phenomena,
Project members are taking an approach based
on chip-scale microsystems and nanosystems to
advance instrumentation by improving sensitivity,
portability, cost, and traceability to fundamental
constants. The research has traditionally focused on
the data storage, electronics, and communication
industries and is currently exploring applications
in medicine and bioengineering. Recent programs
include magnetic manipulation and measurement
of single molecules in microfluidic environments,
engineered radio-frequency tags for magnetic
resonance imaging (MRI) and microfluidics, single
molecule enzymology, precision cantilevers for
transfer standards and intrinsic force measure-
ments, microfabrication of chip-scale atomic
devices, and integration of chip-scale MRI mi-
croscopy systems.

Bio-atomic force microscope for microfluidies experi-
ments on single molecules.

Customer NEEDS

We are developing new methods for magnetic
measurements at the nanometer scale. Examples in-
clude cantilever magnetometers, where a sample is
integrated with the sensor for maximum coupling,
which hold promise for magnetic measurements at
room temperature at the level of 1000 atoms. We
develop: (1) methods for understanding the physi-
cal processes that give rise to the unique properties

_ of nanomagnetic materials, (2) new instrumenta-

tion for nanometer scale MEMS magnetometry,
and (3) new protocols for detecting the distinct
signatures of magnetic nanoparticles.

The medical and security communities are acutely
interested in harnessing the unique properties of
nanomaterials, with nanomagnetism being one
of the key physical characteristics of interest. We
focus on the properties of nanoparticles dispersed
in liquids or solids at the bulk and single-particle
limits, with the ultimate goal of developing them
for new imaging modalities. These include mag-
netic particle imaging (MPI) and MRI for medical
applications, microfluidic devices that use mag-
netic particles for single cell and single molecule
bioassay applications, radio-frequency tags for cell
tracking in research animal models, and forensic
identification of controlled substances.

TECHNICAL STRATEGY

The project’s technical strategy is to develop:
(1) new, ultrasensitive magnetometers based on
MEMS chips, MPI, and MRI, (2) integrated mi-
crosystems and new imaging modalities based on
microscale and nanoscale magnetic particles, (3)
quantitative cantilevers and calibration methods
for quantifying the performance of atomic force
microscopes, (4) magnetic microfluidic platforms
for single-molecule studies, and (5) integrated
microsystems based on atomic transitions.

MEMS Macnetometry of PaTTeRNED

Technical Contact:
John Moreland

Staff-Years (FY 2006):
1.0 professional

0.5 technician

2.0 research associates
1.0 graduate student

Methods for measuring the properties and estimat-
ing the performance of nanomagnetic materials and
devices are in the early development stage. Conven-
tional magnetometers lack the necessary sensitivity
for direct measurement of single nanoparticles or
nanodevices. We target medical and security ap-
plications where we believe a significant impact
could be made in the next five years in developing
new measurement tools for basic research, rapid
detection, assay, and diagnosis; early detection of
diseases; and drug development and approval.

‘Sup-Micrometer-Dots-

Sub-micrometer scale magnetic measurements
have proven to be a challenge for conventional
magnetometers, and new methods are being
employed to probe magnetism on this scale. We
will provide new magnetometers based on highly
specialized MEMS chips fabricated at NIST. Such
instruments will be inexpensive, since MEMS can
be batch-fabricated in large quantities. In addition,
large-scale magnetic wafer properties can be trans-
ferred to smaller MEMS magnetometers so that

Election

BE



sion extrapolation range, an anechoic chamber, a ground screen, and other EM experimental facilities,
as well as excellent computational resources, We welcome proposals in these or related areas that extend
or improve the application of near-field antenna measurement methods.

ANTENNA THEORY AND Measurements II
R. C. Wittmann and M. H. Francis

In spherical near-field scanning, probe pattern information and data measured at points on a spherical
surface are used to determine the fields of a test antenna anywhere beyond the measurement radius
(especially in the far-field zone). Although the theory is well understood, a number of areas need fur-
ther work, including (1) development of more efficient measurement and computation methods; (2)
analysis of and correction for measurement errors; (3) practical pattern correction schemes for general
probes; (4) development of a simplified theory for the “quasi-far-field region” where measurements are
“almost” made in the far field; and (5) extensions of near-field antenna theory to other applications such
as acoustics, field synthesis, and the evaluation of far-field (compact range) measurement systems. We
welcome proposals on these and other topics that extend or improve the application of spherical near-
field measurement techniques.

Hicu-Fie_p Superconpuctor RESEARCH
J. W. Ekin

This research program is interdisciplinary, encompassing the physical, mechanical, and electrical proper-
ties of high-field superconducting materials and composites. Research is conducted on new types of high
current density superconductors and superconductor stabilization that are being developed for high energy
physics accelerators, magnetic fusion systems, and magnetic resonance systems. Experimental programs
include the study of the electromechanical properties of superconductors, high-pinning materials, internal
reinforcement, and advance composite design. Very high-field magnet systems, power supplies, servo-
hydraulic mechanical test systems, and analytic microscopy facilities are available. Theoretical studies
concentrate on flux pinning and the intrinsic effect of strain on the superconducting state.

Hic 7, SurpeRconpucTorR RESEARCH
J. W. Ekin

Aunique feature of this program is that we use our expertise in electromechanical measurements and con-
tact interface studies to work more closely with research laboratories in industry and at major universities
to develop new types of high-T, superconductors for emerging power technologies in transmission lines
and high-power-density rotating machinery. We are interested in all aspects of high-T, superconductor
research, including the mechanical, magnetic field, and electrical limits of the new class of thick-film
YBCO coated conductors. Our film deposition and cleanroom facilities are fully equipped for fabrica~
tion and micropatterning of film conductors, contacts, and research test structures. Particular effort now
focuses on understanding the basic properties of YBCO film superconductors, new reinforced low porosity
Bi-2223 and Bi-2212 superconductors, and MgB, multifilamentary composite conductors.

FERRITIN AND OTHER Macnetic NaANoparTICLES IN PROTEIN SHELLS

| R.B. Goldfarb

Ferritin is nature’s ubiquitous iron-storage molecule, found in species ranging from microbes to man.
It consists of a roughly spherical apoferritin protein shell, inside which iron accumulates in the form
of a ferric oxyhydroxide crystal. The outer diameter is 12 nm, irrespective of the amount of iron stored
within. Although its physical, chemical, and magnetic properties have been studied for more than 60
years, ferritin remains a subject of current research, with many implications for biology and medicine. In
particular, ferritin is an important contributor to T, and T, relaxation, which effectively determine image
contrast in magnetic resonance imaging. Applicant with backgrounds in physical chemistry, chemical
synthesis, magneto-chemistry, magnetometry, nuclear magnetic resonance, and electron paramagnetic
resonance are invited to apply. Equipment available includes a 7-tesla SQUID magnetometer and a 7-
tesla/300-megahertz nuclear magnetic resonance system.



MAGNETODYNAMICS

GoaLs

This project develops instruments, techniques, and
theory for the understanding of the high-speed re-
sponse of coramercially important magnetic materi-
als. Techniques used include linear and nonlinear
magneto-optics and pulsed inductive microwave
magnetometry. Emphasis is on high-frequency
(above 1 gigahertz), time-resolved measurements
for the study of magnetization dynamics under
large-field excitation. Research addresses the
nature of coherence and damping in ferromag-
netic systems and their effects on the fundamental
limits of magnetic data storage. Research on spin-
electronic systems and physics concentrates on
theoretical analysis of spin-momentum-transfer
oscillators. The project provides results of interest
to the magnetic disk drive industry, developers of
magnetic random-access memory, and the growing
spin-electronics research community.

Customer NEEps

Adyances in magnetic information storage are
vital to economic growth and U.S. competitive-
ness in the world market for computer products
and electronic devices. Our primary customers
are the magnetoelectronics industries involved in
the fabrication of magnetic disk drives, magnetic
sensors, and magnetic random-access memory
(MRAM).

Data-transfer rates are increasing at 40 percent
per year (30 percent from improved linear bit
density, and 10 percent from greater disk rota-
tional speed). The maximum data-transfer rate in
these nanometric devices is currently 1 gigabits
per second, with data-channel performance of
over 3 gigahertz (in the microwave region), with
corresponding magnetic switching times of less
than 200 picoseconds. At these rates, a pressing
need exists for an understanding of magnetization
dynamics, and measurement techniques are needed

which magnetization becomes thermally unstable?
We are developing the necessary metrology to
benchmark the temporal performance of new
methods of magnetic data storage.

The spin momentum transfer effect — or “spin
torque” — offers new opportunities and challenges
for the data storage and spintronics industries. In
the commercial disk drive industry, spin torque
degrades the performance of current-perpen-
dicular-to-plane read-head components by driv-
ing unstable dynamics in the read-head sensor
element. However, spin torque may also be used
to fabricate nanoscale on-chip oscillators for
telecommunications devices. We are developing
theory to understand this effect that may be used
to harness the spin momentum transfer effect for
future magnetoelectronic applications.

TECHNICAL STRATEGY
NaNnomacNeTopynamics

Our aim is to identify future needs in the data-
storage and other magnetoelectronic industries,
develop new metrology tools, and do the experi-
ments and modeling to provide data and theoreti-
cal underpinnings. We concentrate on two major
problems in the magnetic-data-storage industry:
(1) data-transfer rate, the problem of gyromagnetic
effects, and the need for large damping without
resorting to high magnetic fields, and (2) storage
density and the problem of thermally activated
reversal of magnetization. This has led to the
development of instrumentation and experiments
using magneto-optics and microwave circuits. Mi-
crowave coplanar waveguides are used to deliver
magnetic-field pulses to materials under test. In
response, a specimen’s magnetization switches, but
not smoothly. Rather, the magnetization vector un-
dergoes precession. Sometimes, the magnetization
can precess nonuniformly, resulting in the genera-
tion of spin waves or, in the case of small devices,

Technical Contact:
Tom Silva

Staff-Years (FY 2006):
1.5 professionals
2.0 research associates

To quantify the magnetic switching speeds of com-
mercial materials.

The current laboratory demonstration record for
storage density is over 30 gigabits per square
centimeter (200 gigabits per square inch). How
much further can longitudinal media (with in-plane
magnetization) be pushed? Can perpendicular re-
cording, patterned media with discrete data bits, or
heat-assisted magnetic recording extend magnetic
recording beyond the superparamagnetic limit at

incoherent rotation. We use several methods to
detect the state of magnetization as a function of
time. These include the following:

mw The magneto-optic Kerr effect (MOKE)
makes use of the rotation of polarization of light
upon reflection from a magnetized film. We have
used MOKE with an optical microscope to measure
equilibrium and nonequilibrium decay of magne-
tization in recording media.



+— forse withthe PEVIM apparatus; allowing ustosi=

150

Contour plots of the x component of magnetization in
a spin-torque nano-oscillator. Left: Vortex mode with
odd symmetry (frequency 17.1 gigahertz); the black
dashed circle in the center represents the point contact
boundary. Right: Radially symmetric mode with even
symmetry (frequency 18.9 gigahertz), when the Oer-
sted field is neglected.

= Magnetization Dynamics Excited by Se-
quence of Large-Amplitude Field Pulses — We
used a time-resolved ferromagnetic resonance tech-
nique to investigate the nonlinear magnetization
dynamics of a 10 nanometer thin Permalloy (Ni-Fe)
film in response to a sequence of large-amplitude
field pulses. The magnetic field pulse sequence
was set at a repetition rate equal to the magnetic
system’s resonance frequency. Both inductive
and optical techniques were used to observe the
resultant magnetization dynamics. We compared
data obtained by this technique with conventional
PIMM. The results for damping and frequency
response obtained by these two different methods
coincide in the limit of a small-angle excitation.
However, when applying large-amplitude field
pulses, there was a substantial increase in the ap-
parent damping. Analysis of vector-resolved SH-
MOKE data indicate that the increase in damping is
correlated with a decrease in the spatial homogene-
ity of the magnetization dynamics. This suggests
that unstable spin-wave generation occurs in the
limit of large-amplitude dynamics.

= Comparison of Microscopic and Spatially
Averaged Magnetization Dynamics — We
adapted a time-resolved magneto-optic microprobe

spacing between magnetic inhomogeneities for
linewidth broadening to be considered localized in
character, in analogy to inhomogeneous broaden-
ing effects for electron spin resonance and nuclear
magnetic resonance. If the inhomogeneities are
spaced any closer, the inhomogeneities contribute
to collective excitations that are not localized at
the site of the inhomogeneity. In other words, the
inhomogeneities act as defects that scatter energy
from the uniform mode into nearly degenerate
magnon modes. Analysis of our data indicates
that the inhomogeneities present in Permalloy are
spaced below the limit for localization, leading us
to conclude that the apparent inhomogeneous con-
tribution to the ferromagnetic damping is actually
the result of a two-magnon scattering process.

= Comparison of Ferromagnetic Resonance
Measurements Using Different Methods — Mi-
crowave stripline (SL), vector network analyzer
(VNA), and PIMM techniques were used to mea-
sure the ferromagnetic resonance (FMR) linewidth
for a series of Permalloy films with thicknesses
of 50 and 100 nanometers. The SL-FMR mea-
surements were made for fixed frequencies from
1.5 to 5.5 gigahertz. The VNA-FMR and PIMM.
measurements were made for fixed in-plane fields
from 1.6 to 8 kilo-amperes per meter (20 to 100
oersteds). The results provide a confirmation,
lacking until now, that the linewidths measured
by these three methods are consistent and compat-
ible. The linewidths in field are a linear function
of frequency. The corresponding linewidth in
frequency shows a weak upward curvature at the
lowest measurement frequencies and a leveling-off
at high frequencies.

Course

Tom Silva developed and taught a graduate level
course on magnetism and magnetic materials at the
University of Colorado—Boulder in spring 2006.
It was attended by physicists and engineers, some
from private industry.

multaneously measure the dynamics at micrometer
and millimeter length scales. The microprobe has a
spatial resolution of one micrometer. Comparison
of the data was used to determine whether the inho-
mogeneous contribution to damping is in the local-
ized or collective (that is, two-magnon-scattering)

limit. These two limiting cases were theoretically
delineated by the Materials Science and Engineer-
ing Laboratory. The theory establishes a minimum

Awarb

U.S. Department of Commerce Silver Medal
(Bill Rippard, Stephen Russek, and Tom Silva)
and EEEL Distinguished Associate Award (Matt
Pufall and Shehzaad Kaka) for the discovery of
mutual phase-locking, external frequency-locking,
and frequency modulation of spin-transfer nano-
oscillators, 2006.



A.E. Cox, J.J. O*Connell, and J.P. Rice, “Initial Results from
the Infrared Calibration and Infrared Imaging of a Microwave
Calibration Target,” Digest Int. Geoscience aud Remote Sensing
Symp. (IGARSS-2006), Denver, CO (August 2006).

D. Williams, H. Khenissi, F. Ndagijimana, K. A. Remley, J.
Dunsmore, P. D. Hale, J, Wang, and'T. $. Clement, “Microwave-
Mixer Measurement with a Sampling Oscilloscope,” IEEE
Microwave Theory Tech. 84, 1210-1217 (March 2006).

R. Ginley, “A Direct Comparison System for Meesuring Low
Frequency Power (100 kHz to 18 GHz),” Proc. Meas. Soi. Conf.
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