RESEARCH HIGHLIGHTS 2009
A publication of the WPI Advanced Institute for Materials Research
RESEARCH HIGHLIGHTS

Bulk metallic glasses: In the zone
Atomic structures: Titanium coming out on top
Superconductors: Poacher turned gatekeeper
Biomimetic surfaces: Like water on a rose petal
Metallic glasses: Throwing light on the insides
Electronic devices: One-way magnetism enhances memory capacity
Superconductivity: Graphite on the rise
Bulk metallic glass: Spiked with silicon
Electron microscopy: What lies beneath
Metallic glasses: Cluster control
Spintronics: Half-metals in full power
Superconductivity: At the boundaries
YOUNG RESEARCHERS

Fusion research gears up
INTERNATIONAL WORKSHOP

Bulk metallic glasses, France 2009
NEWS & EVENTS

WPI-AIMR director scoops RSC Centenary Prize
WPI-AIMR group leader honored by American Physical Society
A boost for integrated microsystems

RESEARCH HIGHLIGHTS 2009
WPI Advanced Institute for Materials Research
The Advanced Institute for Materials Research (AIMR) at Tohoku University in Sendai, Japan is
one of five World Premier International (WPI) Research Centers established with the support of theJapanese Ministry of Education, Culture, Sport, Science and Technology (MEXT). Inaugurated in2007 and coinciding with the 100th anniversary of the founding of Tohoku University, the WPI-AIMR
brings together internationally renowned researchers from Japan and abroad to lead interdisciplinary
collaborative research on new and innovative functional materials technologies at the forefront ofmaterials science.
The WPI-AIMR is composed of four main divisions focusing on bulk metallic glasses, nanophysics,
nanochembio and device/systems construction. Led by Chief Scientist and Institute Director Yoshinori
Yamamoto and supported by an international advisory board, the WPI-AIMR promotes collaboration
among its divisions toward the development of breakthrough technologies bridging such disciplines
as materials science, physics, chemistry and precision, mechanical, electronics and informationengineering.
The WPI-AIMR is host to over 100 leading researchers from across the world including 32 principal
investigators. In addition to the research hub at Tohoku University, the WPI-AIMR collaborates
with research centers in the UK, France, Germany, the US and China. Close ties with other leadinginternational universities are maintained through its adjunct professor and associate professor programs.

AIMResearch
AIMResearch is a new online and print publication that highlights the scientific achievements andactivities of the WPI-AIMR. First published in June 2009, AIMResearch selects the most important
papers from the wealth of research produced by WPI-AIMR scientists throughout the year, distillingthe essence of the achievements into timely, concise and accessible research highlights that are easy-todigest but retain all of the impact and importance of the original research article.
Uploaded monthly to the AIMResearch website in both English and Japanese, AIMResearchhighlights bring the very best of WPI-AIMR research to a global audience of specialists and nonspecialists alike.
AIMResearch also publishes a range of features articles introducing other activities of the WPIAIMR’s research groups. All of the information contained on the AIMResearch website is also available
in Japanese and visitors can register for free monthly email alerts in either Japanese or English so thatthey can keep abreast of the latest developments and discoveries made at the WPI-AIMR.
http://research.wpi-aimr.tohoku.ac.jp/© 2010 Tohoku University

A material world
As institute director of the World Premier International

which we live, now and in the future.

Advanced Institute for Materials Research, it is my very

For a scientist in the twenty-first century, however, it isgreat pleasure to welcome you to this print collection of

not enough simply to investigate, discover and innovate.

research highlights published by AIMResearch in 2009.

The modern researcher must also be able to communicate

Materials science is becoming increasingly importantthe importance and relevance of their work not only toyear on year in terms of both pure and applied research.

their colleagues, but also to scientists active in other fields

From a scientific and technological perspective, materials

and even to non-scientists. But this is not communication

science stands at the intersect point of a whole range offor communication’s sake: greater understanding of thedifferent disciplines, from basic sciences such as chemistryscience stimulates even more fruitful exchange of ideas

and physics through to highly focused applications such

between researchers, raises the overall level of interest in

as photonics and nanotechnology, electron microscopy,

science and engenders greater trust of scientists in society.

superconductor technology, materials catalysts andIt was with this aim — sharing the fruits of our labors at

electronic devices. Some of this research, in the fields

the WPI-AIMR — that we created AIMResearch.

of bulk metallic glasses and semiconductor research,

This collection is only a snapshot of what is being

for example, or the development of materials with one-published on the AIMResearch website every month. I

dimensional magnetic properties, is likely to have a direct

hope that you will visit the site in the near future and read

impact on society in the near future. Other areas, such as

the very latest highlights and features published by theadvanced electron microscopy and ‘spintronic’ devices,

WPI-AIMR (research.wpi-aimr.tohoku.ac.jp). While you

hold the promise of new and better tools and techniques

are there, I would encourage you to register for regular,that will deliver the next generation of scientific advances.

free email alerts so that you need never miss the latest

Materials science then continues to change the world in

information about research from the WPI-AIMR.

Yoshinori Yamamoto
Institute Director
WPI Advanced Institute for Materials Research© 2010 Tohoku University

RESEARCH HIGHLIGHTS

Bulk metallic glasses

In the zone
Nanoscopic shear zones have been identified as responsible for plastic flow in bulk
metallic glass

Metal alloys with a glassy atomic
structure, known as bulk metallic glasses(BMGs), are much stronger than normal
metals and have great promise for avariety of applications. Unfortunately,
they are also less ductile, making themmore susceptible to fracture. To try tounderstand why, Mingwei Chen andcolleagues from the Advanced Institutefor Materials Research (AIMR) at Tohoku
University 1 have conducted the firstexperimental characterization of shear
transformation zones that arise when a
BMG is subject to plastic deformation.
When a conventional metal cools fromits molten liquid state, its atoms arrange
into well-ordered crystalline structures.
This rarely results in a perfect singlecrystal structure; rather, a polycrystalline
matrix consisting of randomly oriented
crystallites is generally formed. Owing to
the weakness of the boundaries between
these grains and other imperfections, theactual mechanical strength of a metal isusually much lower than the theoreticalstrength it would have if it were a perfect
single crystal.
BMGs, on the other hand, are alloys
in which the atoms have not been
given time to arrange into crystallites,
resulting in a non-regular structure
similar to that of ceramic glass. This
circumvents the problems of grainb oundar ies and cr yst al defec ts,
making BMGs much stronger thanconventional metals. However, although
they are less brittle than ceramics,
they are more brittle than most metals.
One of the leading explanations forthis poor ductility is the emergence of‘shear transformation zones’ (STZs)

B
AC

Schematic diagram of the activation of an STZ in a glassy material. Mechanical failure through macroscopic
shear occurs by the accumulation of a critical number of activated STZs on a slip plane.

within a BMG. STZs are nano-scale
volumes of material that undergo plastic
flow (pictured), and the concentrationof stress at STZs is believed to cause
localized shear bands to form, leading
to mechanical failure and poor ductility.
Until now, the nature or even the exact
size of these zones has never beencharacterized. To address this, Chenand his colleagues developed a new‘rate-jump nanoindentation’ techniquefor characterizing the mechanicalbehavior of these structures involving
the measurement and modeling of the
response of a BMG to a micro-sized
diamond indentor with nanoscopic
resolution of force and displacement.
The researchers applied this approachto a variety of different BMGs, which2© 2010 Tohoku University

allowed them to determine the volumesof material involved in the plastic flow ofatomic clusters in an STZ, and to correlate
this with the ductility of the BMG. They
found that BMGs exhibiting the smallest
STZ volumes were also the least ductile.
This observation should allow otherscientists to improve their understanding
and optimize the mechanical performanceof BMGs. It is also a demonstration of
a powerful technique for characterizing
the mechanical behavior of other noncrystalline materials.
1. Pan, D., Inoue, A., Sakurai, T. & Chen, M.W.
Experimental characterization of shear
transformation zones for plastic flow of bulk
metallic glasses. Proceedings of the National
Academy of Sciences 105, 14769–14772 (2008).

RESEARCH HIGHLIGHTS

Atomic structures

Titanium coming out on top
High-resolution electron microscopy settles the problem of the atomic structure at
the surface of titania, an important catalyst material

Precise knowledge of the arrangementof atoms at the surface of a crystal iscrucial for catalytic materials, which
are used to initiate chemical reactions
through interactions at the surface.
Settling existing controversy, Yuichi
Ikuhara and colleagues from the
University of Tokyo in collaboration
with the Advanced Institute for Materials
Research (AIMR) at Tohoku University1
have now determined the atomic
arrangement at the surface of titania(TiO2), which is an important material
for catalytic processes.
Crystalline materials are regular
three-dimensional assemblies ofatoms, and study of the bulk crystal
structure is generally straightforward.
The surface of a crystalline material,
however, is notoriously difficult to
study, as the disruption to the perfect
crystal symmetry leads to compromises
in the positions and chemical bondsof the surface atoms. “Determining
the surface structure is very importantfor understanding the nature and themechanism of the catalytic properties,”says Ikuhara.
Although there have been many
proposals for the surface structureof titania, it has remained difficult todetermine the positions of top surface
atoms precisely by experimental
observations. The researchers were able toderive the titania surface structure for the
first time through a combination of highvoltage electron microscopy (HVEM)
and scanning electron microscopy
techniques (pictured).
The surface structure was studied
with atomic precision from two

[001]

5Å
Å

High-resolution HVEM image of a TiO2 (110) surface observed from the [001] direction (black corresponds toTi sites). Structural reconstruction is visible at the surface.

directions, and the three-dimensional
image thus obtained was comparedwith two structures that have recently
been proposed in theoretical studies.
In one of the models, the outer surface
is comprised predominantly of oxygen
atoms, whereas in a more recent study,titanium was predicted to be locatedat various positions near the surface
such that the surface composition ismore balanced between oxygen andtitanium. The experimental results clearly
confirmed the latter prediction.
The findings suggest that titanium
plays a more active role on the surfaceof titania than previously thought,
which provides valuable feedback fordeveloping a better understanding of
the reaction kinetics on the surfaceof titania. “I believe that our findings
will contribute significantly to ourunderstanding of the surface kinetics,”
comments Ikuhara.
In catalytic applications, the surface oftitania is often functionalized with noble
metals such as gold or platinum, which
act as co-catalysts. As a next step it will
be important to study the structure of
the interfaces between these metals andtitania. “This,” says Ikuhara, “will enable
us to understand the origin and nature of
their catalytic properties.”

1. Shibata, N., Goto, A., Choi, S.-Y., Mizoguchi, T.,
Findlay, S.D., Yamamoto, T. & Ikuhara, Y. Direct
imaging of reconstructed atoms on TiO2 (110)
surfaces. Science 322, 570–573 (2009).

3© 2010 Tohoku University

RESEARCH HIGHLIGHTS

Superconductors

Poacher turned gatekeeper
An insulating material has been converted into a superconductor using only anelectrical field — without the need for chemical doping

400

VG = 3.00 V

300

Rs (Ω)

Superconductivity, the capacity of certain
materials to conduct electricity withzero resistance and therefore no loss ofenergy below a critical temperature, isa physical phenomenon of profoundimportance with numerous scientific andpractical applications. Superconductivity
is controlled by the density of charge
carriers within a material — electrons in
the case of negative charge and ‘holes’
for positive charge. Typically, materials
are converted into superconductors byintroducing impurities into the crystal
lattice by chemical doping. However, suchmodification is often irreversible, andinevitably introduces structural disorder.
An alternative approach for making
superconductors involves tuning thedensity of charge carriers of a material
by applying an external electric field.
This method has made it possible toconvert metals and chemically doped
insulators into superconductors, but
attempts with non-doped insulators
have so far been unsuccessful due to the
low charge densities in these systems.
Now, a team of scientists led by Masashi
Kawasaki and Kazunori Ueno from theAdvanced Institute for Materials Research(AIMR) at Tohoku University 1 havesuccessfully used an electrical method to
induce superconductivity in strontium
titanate (SrTiO 3 ), which is better
known as an insulator. “This work is
the first demonstration of converting an
insulating material to a superconducting
one purely by an electric field. That was
dreamed by people for more than 50
years,” says Kawasaki.
The researchers electrically doped
SrTiO 3 using a modified electricalTcmid = 0.4 K

Apply bias voltage

Pt GateElectrolyte

200

ClO4
K+

100

Superconductivity
in an insulator

SrTiO3
0

0

0.2

0.4

0.6

0.8

1.0

1.2

T (K)
Graph showing the abrupt disappearance of resistance (Rs) in SrTiO3 as the temperature drops to 0.4 K at
a gate voltage (VG) of 3 V. Inset shows a schematic diagram of the structure of the electric double-layertransistor incorporating the SrTiO3.

method inspired by electrochemicalcells. Writing in Nature Materials, theresearchers describe their work in which
they constructed an ‘electric doublelayer transistor’ field-effect device. In
a conventional electrochemical cell, anelectrolyte is set between two electrodes,
and the application of an electrical field
across the electrodes leads to charge
separation as the positive and negativeions within the electrolyte migrate toward
opposite electrodes. The researchers
modified this technique by replacing
one of the electrodes with SrTiO3. When
immersed in an organic electrolyte witha platinum wire electrode, the resistanceof the SrTiO3 declined sharply at voltages
above 2.5 V, showing that the system wasbehaving like a conducting metal. Upon
dropping the temperature to 0.4 K — nearabsolute zero — the normally insulating4© 2010 Tohoku University

SrTiO 3 became a superconductor(pictured). Examination of the SrTiO3
surface revealed that this transition isdue to the accumulation of positive
charge near the surface rather than toelectrochemical reactions. Furthermore,this electrically doped SrTiO3 material
exhibited superconducting behavior
different from that of the chemically
doped samples.
“Our study provides another way
to search for superconductivity, andconsiderably widens the choice ofcandidate materials for possible newsuperconductors,” says Ueno.
1. Ueno, K., Nakamura, S., Shimotani, H.,
Ohtomo, A., Kimura, N., Nojima, T., Aoki, H.,
Iwasa, Y. & Kawasaki, M. Electric-field-induced
superconductivity in an insulator. Nature
Materials 7, 855–858 (2008).

RESEARCH HIGHLIGHTS

Biomimetic surfaces

Like water on a rose petal
Metal–polymer surfaces inspired by natural systems can be made to retain or repel
water droplets

Picture a rose, in full bloom, after a rain
shower. Water droplets bead up on thepetals, but they do not slide off — instead,the petals grip the droplets in place,even if the flower is inverted. The secretto the water-retaining power of rose
petals? A microstructured surface withboth hydrophilic (water attracting) andhydrophobic (water repelling) regions.
The field of biomimetics seeks to
reproduce natural technologies, suchas the adhesion properties of rose
petals, with synthetic materials. Now,
Masatsugu Shimomura and co-workers
from the Advanced Institute for Materials
Research (AIMR) at Tohoku University1
have developed a new biomimetic surface
composed of self-organized metal–
polymer structures, which can be madeto repel or cling to water droplets.
According to Daisuke Ishii, the leadauthor of the study, creating a biomimetic
material with adjustable wettability
requires precise dimensioning of thehydrophilic and hydrophobic surface
patterns. If the patterns are too large,
the regions act independently, making
it impossible to control water droplets.
Similarly, patterns that are too small
compared to the size of the droplet havelittle effect on the droplet’s behavior.
“O ur sur face is comp os ed of
micrometer-sized hydrophobic–hydrophilic patterns,” says Ishii. “As a result,water droplets are simultaneously repelled
and adhered on our hybrid surface.”
The researchers combined hydrophilic
metal domes with super-hydrophobicpolymer spikes to create their new
biomimetic surface. “By fabricating a
polymer and metal hybrid, we hoped to

10 μm

Scanning electron microscopy image of a biomimetic surface composed of hydrophilic metal domes andhydrophobic polymer spikes.

make a functional surface with wettability
that responds to external stimuli,”
explains Ishii.
First, the scientists cast a thinpolystyrene-based film onto a glass
honeycomb-patterned template to form
hexagonally ordered microcavities. This
honeycomb film was then coated withnickel metal, which filled many of thecavities. By peeling off the polymer film
layer, the researchers obtained a series ofmetal domes and empty cavities amidst
an array of polymer spikes (pictured).
Ishii’s team prepared a range ofthese biomimetic surfaces by varying
the surface metal concentration. They
found that altering the metal dome
coverage from 0% to 25% changed thesurface’s properties from completely
water-repellent to as water-adherent as arose petal.
Manipulating wettability throughexternal stimuli is the ultimate
goal of the researchers. “Adhesion
properties can be controlled by using
the electric and magnetic energies ofthe metal microstructures,” says Ishii.
“We will demonstrate micro-droplet
manipulation on the biomimetic surfaces
for new micro-fluidic and lab-on-achip devices.”
1. Ishii, D., Yabu, H. & Shimomura, M. Novelbiomimetic surface based on a self-organized
metal–polymer hybrid structure. Chemistry ofMaterials 21, 1799–1801 (2009).

5© 2010 Tohoku University

RESEARCH HIGHLIGHTS

Metallic glasses

Throwing light on the insides
High-energy light reveals the hidden internal structure of metallic glass

Metallic glasses, made by carefully
cooling hot metal alloys so that theysolidify without crystallizing, promise
to revolutionize the materials industry.
Thanks to an irregular, tightly packed
internal arrangement of atoms, metallic
glasses are moldable like plastic whenheated, yet stronger than typicalcrystalline alloys.
Now, a te am of inter national
researchers from the Advanced Institutefor Materials Research (AIMR) at Tohoku
University in Japan and the Institut
Polytechnique de Grenoble in France1
has used high-energy light to probe theinternal structure of a metallic glass ofzirconium (Zr) and copper (Cu). The
results provide a guide for producing
thicker alloy glasses with enhanced
functionality.
The researchers, led by Alain Yavari,used a high-energ y synchrotron
X-ray source to ricochet photons off
atoms buried deep inside a sample of
Zr–Cu metallic glass. Mathematicalinterpretation of the resulting X-ray
diffraction signals gave a description of
how pairs of Zr–Zr, Cu–Cu and Zr–Cu
atoms were distributed within the glass.
By taking measurements of alloys withvarious compositions, the scientists wereable to correlate changes in glass stability
with changes in the atomic structure.
According to Yavari, the Zr–Cu metallic
glass is an ‘ideal solid solution’ — that is,because the interactions among atoms are
weak, the atoms can distribute randomly
within the glass.
The random distribution of atoms
creates a densely packed internal
structure, but it also reduces the alloy’s

Schematic diagram showing how the atoms in Zr–Cu metallic glass form icosahedral clusters that pack tightly
together by sharing faces (left) or edges (right).

resistance to crystallization — only verythin glasses can be cast from Zr–Cu
mixtures. Recently, however, scientists
found that adding a third component,
aluminum (Al), to the hot alloy allowed
stronger glasses to be cast at thicknessesof up to several millimeters.
In contrast to the ideal solution
character of Zr–Cu, the researchers
found that Zr–Cu–Al metallic glasses
deviated markedly from ideal behavior.
They observed that the Zr–Cu–Al glasses
were comprised of finite regions ofatomic order, providing the extra support
needed to form thicker glasses. Theseordered regions are believed to form due
to attraction between the outer electronsof aluminum atoms and the larger
zirconium atoms. The atoms arrange inshells resembling icosahedra, which pack
together tightly in the glass (pictured).
Yavari and his colleagues have previously

6© 2010 Tohoku University

observed the formation of such clusters inother Zr–Cu alloys.
The use of synchrotron light, Yavarisays, was highly advantageous foranalyzing the Zr–Cu–Al metallic glasses.
Whereas conventional X-ray beams arecompletely absorbed at the surface of thematerial, light produced by a synchrotron
has sufficient energy and intensity
to penetrate into even thick samples,
providing a deeper understandingof the unique internal structure ofmetallic glasses.
1. Georgarakis, K., Yavari, A.R., LouzguineLuzgin, D.V., Antonowicz, J., Stoica, M., Li, Y.,
Satta, M., LeMoulec, A., Vaughan, G. & Inoue, A.
Atomic structure of Zr–Cu glassy alloys anddetection of deviations from ideal solution
behavior with Al addition by X-ray diffraction
using synchrotron light in transmission. Applied
Physics Letters 94, 191912 (2009).

RESEARCH HIGHLIGHTS

Electronic devices

One-way magnetism enhances
memory capacity
A thin alloy film with one-dimensional magnetic properties could pave the way forhigher capacities of nonvolatile memory

300

200

Perpendicular100

M (emu/cm3)

Magnetic random access memory(MRAM) consists of submicron-sized
elements — magnetic tunnel junctions(MTJs) — that can be ‘written’ into
one of two different magnetization
states representing individual bits of
information (‘0’ and ‘1’). The obvious way
to increase memory capacity is to makethese MTJs smaller, but this can also
make them less stable.
Now, Feng Wu, Terunobu Miyazaki
and co-workers at the Advanced Institutefor Materials Research (AIMR) and theDepartment of Applied Physics at Tohoku
University1 have developed a thin alloy
film that could improve the stability ofhigh-capacity MRAM by restricting themagnetization of MTJ memory layers tojust one direction. The film could also
have applications in spintronic devices,which exploit the intrinsic spin ofelectrons as well as their charge.
“Making smaller MTJs to support
higher memory capacity has been a
successful approach,” says Wu. “Today,
however, MTJs have become so smallthat further shrinkage would cause themagnetization of the individual MTJs to
be unstable and flip spontaneously. So thememory would erase itself.”
One way of getting round this problem
is to use a material with perpendicularmagnetic anisotropy (PMA). Suchmaterials show a preference formagnetization in only one direction —perpendicular to the film. In PMA films,
the memory bits are therefore more stable
than usual against small, random energy
fluctuations from the environment.
What’s more, MRAM based on PMA
films with large spin polarization can

In-plane
0

–100

–200

–300

–50

–25

0

25

50

H (kOe)Graph showing the magnetization (M) of thin Mn2.5Ga films versus the applied magnetic field (H). When thefield is applied perpendicular to the film (black), the film quickly reaches a maximum (saturation) magnetization,
but when the field is applied in the plane of the film (red), the magnetization cannot be saturated. This
‘perpendicular magnetic anisotropy’ could be ideal for magnetic data storage and spintronic applications.

be accessed faster than those based on
existing small-spin-polarized PMA films
because the MTJs have ‘giant’ tunnel
magnetoresistance. “MRAM containing
MTJs with a PMA memory layer isthe most likely candidate for the next
generation of universal memory,” says Wu.
Wu’s team fabricated their new PMA
film from an alloy of manganese andgallium (Mn2.5Ga). They deposited one
atomic layer at a time using a magnetron
sputtering technique, which allowed theatoms to form a well-ordered tetragonal
crystal structure. Interestingly, the alloy
exhibits ferromagnetism even though its
constituent metals do not.
“In our alloy, the distance between
manganese atoms is much larger thanthat in manganese metal,” says Wu.
“Thus, ferromagnetic properties can befound. Our alloy is also predicted to havelarge spin polarization.”
The researchers found that the Mn2.5Ga
film only became magnetized whena magnetic field was applied at rightangles to the film, indicating strong PMA(pictured). The large spin polarization ofthis PMA film makes it ideal for MRAM
and spintronic devices.
“Now, we are fabricating MTJs using
this material as a memory layer, which is
crucial for the realization of gigabit-class
MRAM,” says Wu.

1. Wu, F., Mizukami, S., Watanabe, D., Naganuma, H.,
Oogane, M., Ando, Y. & Miyazaki, T. Epitaxial
Mn2.5Ga thin films with giant perpendicularmagnetic anisotropy for spintronic devices.
Applied Physics Letters 94, 122503 (2009).

7© 2010 Tohoku University

RESEARCH HIGHLIGHTS

Superconductivity

Graphite on the rise
High-resolution spectroscopy experiments reveal important clues toward theunderstanding of superconductivity in graphite compounds

1 mm
1ky(Å–1)The discovery of superconductivity
at unusually high temperatures in thegraphite intercalation compounds
C 6Yb and C 6Ca has spurred intense
efforts to understand the nature ofsuperconductivity in these materials.
Researchers from the Advanced Institutefor Materials Research (AIMR) andthe Department of Physics at Tohoku
University 1 have now contributed
an important clue to the origin of
superconductivity in graphite compounds
by determining the size and nature of
the tell-tale gap in the superconducting
energy spectrum.
C6Ca (pictured left) is part of a larger
family of layered materials in whichatoms such as calcium are intercalated
between graphite sheets. Some of thesegraphite intercalation compounds were
found to be superconductive more than
40 years ago. However, the recently
discovered C6Ca is special, as it remains
superconductive to much higher
temperatures, up to 11.5 K.
To unravel the origin of thisbehavior, the researchers compared
the electronic states of C6Ca (pictured
right) with those of regular graphite.
They measured the small differences
between these compounds using a
special high-resolution photoemission
spectrometer at Tohoku University. “Theenergy resolution of our spectrometer isworld-leading and essential to observe
the superconducting gap,” comments
Takashi Takahashi, who led theresearch team.
The high-resolution experiments
uncovered important differences
between graphite and C6Ca. In particular,

High

0

–1

–1

0

1

Low

kx(Å–1)
Photograph of a C 6Ca crystal (left) and electronic states of superconducting C 6Ca as imaged by highresolution photoemission spectroscopy (right).

the experiments revealed not only theenergetic states associated with thecarbon atoms in the graphite layers, butalso those of the calcium intercalation
layers. The researchers were thus able
to observe the changes in the interlayer
energy states as the material wascooled to below the superconducting
onset temperature.
The theoretical expectation was thatthe onset of superconductivity could beobserved by the opening of a gap in themeasured energy states. Indeed, this iswhat the researchers observed. However,
the gap was seen only for the electronic
states of the calcium interlayers —not for the in-plane states of thegraphite sheets.
These findings provide clear evidenceof the important role of the interlayer.
The calcium atoms ‘donate’ electrons to

8© 2010 Tohoku University

the graphite layers, but the experiments
also suggest that this strong coupling
between the calcium electrons and thecarbon atoms could explain the higher
superconducting temperature of C6Ca.
The importance of these findings
extends beyond the graphite intercalation
compounds. The results may also
provide important clues toward theunderstanding of other layered systems,
such as the high-temperature cuprate
superconductors. In addition, says
Takahashi, “the knowledge we obtained
may eventually also lead to the discoveryof new superconductors with even higher
transition temperatures.”

1. Sugawara, K., Sato, T. & Takahashi, T. Fermisurface-dependent superconducting gap in
C6Ca. Nature Physics 5, 40–43 (2009).

RESEARCH HIGHLIGHTS

Bulk metallic glass

Spiked with silicon
The incorporation of small amounts of silicon into a metallic glass enhances ductility
without inhibiting its glass-forming ability

Bulk metallic glasses (BMGs) are metalalloys that have been cooled such thatthey solidify without crystallizing to form
an ordered lattice. Unlike conventional
metals, they soften and flow readily
at moderate temperatures, allowing
them to be cast or molded into intricate
shapes. This unique processability, andtheir high strength, wear and corrosion
resistance, make these materials attractive
for application in biomedical andmicroelectromechanical devices.
Despite being stronger and more wearresistant than conventional metals, somemetallic glasses are also brittle. Now, Na
Chen from Tohoku University’s Advanced
Institute for Materials Research (AIMR)
and collaborators1 have introduced small
amounts of silicon (Si) into a metallic
glass combining palladium (Pd), nickel(Ni) and phosphorus (P) to create analloy with enhanced glass-forming ability
and ductility.
Noting that an exceptionally ductile
metallic glass of Pd–Si had beendeveloped previously2, and that binary
alloys of palladium or nickel with either
silicon or phosphorous form similarphases on cooling, the researchers
expected that the addition of silicon could
also improve the ductility of the ternary
Pd–Ni–P alloy without significantly
affecting its glass-forming ability.
To produce their alloy, the team sealed
well-defined compositions of high-purity
metal powders in quartz tubes underhigh vacuum, and melted the mixtures
homogeneously at 1,323 K. They thencooled the tubes in water to solidify
the Pd–Ni–Si–P ingots. Finally, theymelted the ingots and cast the alloy into

800 nm3 μm

Scanning electron microscopy images showing wavy nanometer- and micrometer-sized steps induced by apropagating crack during failure.

2 mm-diameter cylinders.
Chen and her colleagues found that,
under compression, the Pd–Ni–Si–P
alloy could tolerate three times as muchstrain as the original Pd–Ni–P alloy
before breaking. The broken Pd–Ni–Si–P
surfaces displayed wavy nanometerand micrometer-sized steps (pictured).
“These steps are usually observed on
the fracture surface of brittle materials,”
explains Chen. “But in the case of the Pd–
Ni–Si–P metallic glass, the nanoscale andmicroscale wavy steps were formed at the
final stage of the fracture.”
The researchers showed that Pd–Ni–P
displays two crystallization stages atdifferent temperatures. When they added
as little as 5% silicon, however, only oneof those stages remained. They therefore
suggest that the addition of silicon to
Pd–Ni–P traps the metals in a liquidlike arrangement where the atoms bindloosely to each other.

“Compared to metallic additives,
silicon is a much smaller atom, andthus has a large atomic size differencewith the main constituents, palladiumand nickel, which favors the formationof a non-periodic dense packing
structure and suppresses crystallization,”
explains Chen.
The res earchers are currently
focusing on developing other ductile
and biocompatible BMGs and plan to
use these high-performance, durable
materials to manufacture small devices
for microelectromechanical systems.
1. Chen, N., Louzguine-Luzgin, D.V., Xie, G.Q.,
Wada, T. & Inoue, A. Influence of minor Si
addition on the glass-forming ability andmechanical properties of Pd40Ni40P20 alloy. Acta
Materialia 57, 2775 (2009).
2. Yao, K.F., Ruan, F., Yang, Y.Q. & Chen, N.
Superductile bulk metallic glass. Applied Physics
Letters 88, 122106 (2006).

9© 2010 Tohoku University

RESEARCH HIGHLIGHTS

Electron microscopy

What lies beneathA technique for imaging impurity atoms at a buried interface provides a useful toolfor understanding the behavior of polycrystalline materials

The composition and structure of
the interfaces between crystallites
in a polycrystalline material play animportant role in determining thematerial’s properties and behavior. In
electronic devices and microcomputercircuits, it is often the electronic
properties of these interfaces, rather thanthose of the bulk materials, that form
the basis for device operation. One wayof controlling the characteristics of theinterfaces is to add small amounts ofimpurities as ‘dopants’.
As the size of devices and material
structures approaches nanometer scales,
the influence of interfaces and dopant
atoms becomes ever more significant.
However, because dopant atoms areusually buried within the bulk material, it
is difficult to obtain accurate information
about their distribution at an interface, orthe structure of the surrounding material.
To address this issue, Yuichi Ikuhara
from the Advanced Institute for Materials
Research (AIMR) at Tohoku University
and colleagues from the University ofTokyo 1 have developed a techniquethat uses an electron microscope to
image the location and local structureof individual dopant atoms within aburied interface.
To demonstrate their approach, theresearchers first doped an alumina
surface with a low concentration of
yttrium, which is known to strengthen
the boundary between alumina crystals.
This surface was then buried under asecond alumina layer, added directly
onto the first layer by diffusion bonding.
The sample was subsequently imaged
using a scanning transmission electron

1 nm
Scanning transmission electron microscopy image of the interface between two yttrium-doped aluminumoxide crystals showing the distribution and structural ordering of yttrium atoms (yellow spots). Individual
yttrium atoms are 0.3–0.5 nm apart.

microscope — but in a slightly different
way to how electron microscope images
are usually taken.
Electron microscopy of crystalline
materials is commonly carried out
by directing an electron beam along
one of the sample’s ‘strong channelingaxes’ — particular directions in a crystal
along which electrons can travel easily.
This procedure usually improves theclarity of the images obtained, but canalso conceal the presence of impurities.
Instead, Ikuhara and his colleagues
imaged their sample at an angle fromthese axes, which enabled them to obtainclear, high-contrast images of the yttrium

10© 2010 Tohoku University

atoms at the buried interface (pictured).
The ability to collect atomic-scale
information about interfacial make-up
and structure should enable researchers
to better understand, and therefore
better control, the doping of materialinterfaces. This in turn should help themto more easily engineer and optimize theproperties of polycrystalline materials
and the devices that rely on the behaviorof the interfaces among crystallites.
1. Shibata, N., Findlay, S.D., Azuma, S., Mizoguchi, T.,
Yamamoto, T. & Ikuhara, Y. Atomic-scale imaging
of individual dopant atoms in a buried interface.
Nature Materials 8, 654–658 (2009).

RESEARCH HIGHLIGHTS

Metallic glasses

Cluster control
Atomic-scale heterogeneity makes a better metallic glass

Solid metals usually exist as wellordered crystals, but in recent years
researchers have also produced stiff,
strong, disordered metal alloys known asbulk metallic glasses (BMGs). However,it remains unclear exactly why certain
combinations of metals form BMGs more
readily than others.
Now, Takeshi Fujita, Mingwei Chen
and co-workers at Tohoku University’s
Advanced Institute for Materials Research(AIMR) and the Miyagi National College
of Technology in Natori1 have observedthat when more than two types of metals
are combined, their atoms may arrange
in different types of clusters that aid
the formation of a BMG. “Bulk metallic
glass is a new type of high-strength
material for engineering,” explains Chen.
“It is also very easy to fabricate into
various nanostructures in a supercooled
liquid state.”
The team’s latest work was promptedby experiments showing that a twometal alloy is more likely to form a BMG
structure when small amounts of a third
metal are added. However, it had so
far remained difficult to scrutinize thestructure of a multi-component BMG.
Fujita, Chen and their colleagues wereable to examine the atomic structureof copper–zirconium (Cu–Zr) alloy
samples containing varying amounts ofadded silver through the use of extended
X-ray absorption fine structure (EXAFS)
spectroscopy at the incredibly powerful
SPring-8 synchrotron radiation facility in
Hyogo, Japan.
“Without the advanced synchrotron
source, we could not have detected theatomic structure of these disordered

Ag

Cu

Zr

The atomic configuration in a Cu–Zr–Ag metallic glass. Clusters centered by sliver atoms link together sharing
the surrounding shell atoms.

solids,” says Chen. “Our colleagues
in Natori helped us to interpret the
EXAFS spectra. I think multidisciplinary
collaborations are very important intoday’s cutting-edge research.”
By combining their X-ray spectra withcomputer simulations, the researchersconcluded that the atoms in theircopper–zirconium–silver (Cu–Zr–Ag)
BMG arranged themselves into two
main types of structure: clusters withsilver atoms at the center surrounded bya shell rich in zirconium, and clusters
rich in copper throughout (pictured).
The atomic-scale heterogeneity favors
glass formation.
These two types of clusters were seen
in both the supercooled liquid and thesolid glass state. Moreover, the fact thatthe clusters are close to the ideal sizes
for efficient packing means that they

represent an important step in glass
formation. Different to conventional
atomic clusters, the clusters in metallic
glasses are not individually isolated.
Instead, they always share ‘overlap’ atoms
with neighboring clusters to form a dense
and connected packing.
The findings highlight the importanceof structural heterogeneity in forming
amorphous solids. More generally,
the results challenge the traditional
notion that an atom in a solid usually
prefers to be surrounded by atoms ofdifferent types.
1. Fujita, T., Konno, K., Zhang, W., Kumar,V., Matsuura, M., Inoue, A., Sakurai, T. &Chen, M.W. Atomic-scale heterogeneity ofa multicomponent bulk metallic glass withexcellent glass forming ability. Physics Review
Letters 103, 075502 (2009).

11© 2010 Tohoku University

RESEARCH HIGHLIGHTS

Spintronics

Half-metals in full power
The spintronic performance of half-metal Heusler alloys can be enhanced bycomposition engineering

Ta
Controlling electron spin, in addition to
the use of electrons as a charge carrier,may one day lead to a new generationof advanced electronic devices. For
example, we can envisage transistors
based on currents with a well-defined
spin orientation, or logic devices in which
the magnetization is controlled throughelectrical currents.
Essential for the development of such‘spintronic’ devices are materials withsuitable magnetic properties, such asa high degree of spin polarization anda high Curie temperature (T C) — thetemperature above which the materialceases to be a ferromagnet. These criteria
are satisfied by several intermetallic
compounds with a specific crystal
structure known as Heusler alloys.
Terunobu Miyazaki and colleagues at
the Advanced Institute for Materials
Research (AIMR) and the Department
of Applied Physics at Tohoku University1
have now constructed high-performancedevices based on Heusler alloys with thecomposition Co2FexMn1–xSi.
The iron-free alloy Co 2MnSi has ahigh T C (985 K) and is a half-metal;that is, a material in which electrons are
conducting if their spin is one direction,and non-conducting if the spin is in the
opposite direction, which is ideal for the
injection of spin-polarized electrons.
The manganese-free alloy Co2FeSi, on
the other hand, has an even higher TC(1,150 K), but its status as a half-metal
is ambiguous. The team from Tohoku
University showed that certain mixturesof these two alloys, with a mixed iron/manganese composition, have a Curie
temperature higher than 985 K but retain

Cu
SiO2

Heusler alloy
SiO2

Ta
Ir22Mn78
Co75Fe25
Al-O
Co2Mn1–xFexSi
Cr
MgO

Mn/Fe

Si

Co

Schematic representation of the magnetic tunnel junction device used in the experiment (left), and aschematic illustration of the crystal structure of the Heusler alloy (right).

the half-metal character of Co2MnSi.
The team studied magnetic tunnel
junctions consisting of two magnetic
electrodes and a tunneling barrier,where one of the electrodes was madeof the Co 2 Fe x Mn 1–x Si Heusler alloy(pictured). They looked at how thetunnel magnetoresistance (TMR) — theresistance due to electrons tunnelingfrom the Co 2Fe xMn 1–xSi through thebarrier in a magnetic field — changed
when they varied the amounts of ironand manganese in the alloy. The TMR
first increased with the addition of iron,from 67% at x = 0 to a maximum of 75%
for compositions between x = 0.4 andx = 0.6, but then dropped to 46% at x = 1.
The researchers suggest that the high ironcontent (high x) causes the compound tostop being a half-metal and the tunneling
electrons to become less polarized.
The team also measured the ‘Gilbert
damping constant’ of their Co2FexMn1–xSi
compounds. This parameter, related to12© 2010 Tohoku University

the relaxation of magnetization, should be
low for materials used in magnetization
switching. They obtained the minimum
value for the alloy with a compositionof x = 0.4, which also indicates that thematerial with this iron content is still a
half-metal.
Shigemi Mizukami from the researchteam explains that “engineering of thehalf-metallicity and damping properties
for these alloys is required for actual
device design.” In his view, the resultsof their work on Co 2Fe xMn 1–xSi will
stimulate further experimentation to
obtain Heusler alloys with even higher
spin-polarization and lower damping in
the near future.
1. Kubota, T., Tsunegi, S., Oogane, M., Mizukami, S.,
Miyazaki, T., Naganuma, H., & Ando, Y. Halfmetallicity and Gilbert damping constant in
Co2FexMn1–xSi Heusler alloys depending on thefilm composition. Applied Physics Letters 94,
122504 (2009).

RESEARCH HIGHLIGHTS

Superconductivity

At the boundaries
The properties of a new class of superconductors are determined by the energy
distribution of electrons

0.1

Binding energy (eV)T h e phy s i c a l char a c te r is t i c s ofsuperconductors, such as thedisappearance of electrical resistivity
at very low temperature, are wellknown. Yet when it comes to thefundamental mechanism that drives
such behavior, particularly for the
recently discovered class of ‘hightemperature’ superconductors, many
open questions remain. Researchers
from Tohoku University’s Advanced
Institute for Materials Research (AIMR)
along with international collaborators1
have now revealed the significant
role of interactions between electrons
at different electronic states in the
superconducting properties of the ironbased ‘pnictide’ superconductors.
The iron-pnictide superconductors,
discovered just last year, share many
commonalities with the closely related
and well-known copper oxide-based
superconductors (the ‘cuprates’). Bothmaterial classes have a complex twodimensional layered structure that forms
the basis for their superconductivity, andboth begin to superconduct at relatively
high temperatures (near 50 K).
The high-energy electrons responsible
for superconductivity fill certain energy
states at the top of what is known as the‘conduction band’. These states can beplotted in three dimensions as a ‘Fermi
surface’ that describes the crystal’s
electronic properties in relation to thesymmetry of the crystal lattice and theoccupation of various energy levels.
Fermi surfaces can be a single object,such as a sphere, or an arrangement ofsmall unconnected shapes.
Using an ultrahigh-resolution photo-

0.2

High
0.3

0.4

Wave vectorctor
Wave ve

Low

Fermi surfaces for an iron-pnictide superconductor. The color gradient shows photoemission measurements,
and the solid red and blue lines indicate the calculated Fermi surfaces. The strongly interacting parts of the
Fermi surfaces are indicated by a red arrow.

emission spectrometer at Tohoku
University, which allowed the electronic
states to be resolved in fine detail, theresearchers studied the relationships
among the individual parts of the complex
arrangement of Fermi surfaces in apnictide superconductor (pictured). Theyobserved that the interaction between
small Fermi surfaces — called nesting — isstrong for this class of superconductors.
“Our study has definitely established thatFermi surface nesting is an essential anduniversal feature for superconductivity
in the pnictides,” explains Takashi
Takahashi, who led the research team.
Pnictide superconductors withstrong interactions were found to havea higher superconducting transition
temperature than those exhibiting
weak interactions. The researchers also
found that Fermi surface nesting plays
a much stronger role in the pnictides
than the cuprate superconductors, eventhough the underlying mechanisms ofsuperconductivity are related.
According to Takahashi, based on
this discovery of important differences
between pnictides and cuprates, further
studies of samples with different crystal
structures are needed to determine
precisely which electronic states leadto strong nesting and high transition
temperatures. Ultimately, he adds, “bysearching for new superconductors
in which the Fermi surface nesting
condition is well satisfied, we may able
to find superconductors with higher
transition temperatures.”1. Terashima, K., Sekiba, Y., Bowen, J. H.,
Nakayama, K., Kawahara, T., Sato, T., Richard, P.,
Xu, Y.-M., Li, L.J., Cao, G. H., Xu, Z.-A., Ding, H.
& Takahashi, T. Fermi surface nesting induced
strong pairing in iron-based superconductors.
Proceedings of the National Academy of
Sciences 106, 7330–7333 (2009).

13© 2010 Tohoku University

YOUNG RESEARCHERSYOUNG RESEARCHERS

Fusion research gears up
The unconstrained research environment of the WPI-AIMR prompts young researchers to avidly seek collaboratorsfrom different groups, leading to one interesting project idea after another.

Every Friday evening, dozens of students,
researchers and principal investigators
flock into the lobby of the WPI-AIMR’s
brand-new research building. Younger
researchers especially look forward to theregular gathering as a great opportunity
to mingle and chat freely with colleaguesof any rank over coffee and cookies,
where conversations can lead to new
ideas and even joint projects.
The weekly ‘Tea Time’, a kind of
informal event still unusual at Japanese
research institutes and universities, is thelatest example of an undertaking by the
WPI-AIMR to provide young researcherswith an unconstrained and stimulating
environment to allow their potential tobloom. The WPI-AIMR’s endeavors havealready begun to show fruit in the formof spontaneous and creative research
activities, and more than 25 ‘fusion
research’ projects have been created at
the institute of 120 researchers since
the first call for proposals was issued in
March 2009. Fusion research is designed
to encourage interdisciplinary interaction
and collaboration among researcherswith different backgrounds in an effort tospur synergies that could pave the way for
new materials science.

Yu-Ching Lin, assistant professor, Device/System Group

Attractive research environment“Fusion research is one of the main
reasons I came here,” says Yu-Ching
Lin, an assistant professor of theDevice/System Group specialized
in microelectromechanical systems(MEMSs). Before the WPI-AIMR was
established, the Taiwanese researcher spenttime at the Tohoku University School ofEngineering, and later at the Fraunhofer
Research Institution for Electronic
Nano Systems in Chemnitz, Germany.
Having studied practical and theoreticalengineering, Lin reached a point where she
felt the need to learn the basic materials
science required to invent novel MEMS
devices. Around that time, her supervisor,
Thomas Gessner, director of the
Fraunhofer ENAS who now concurrently
serves as a principal investigator at the
WPI-AIMR, recommended that she apply
for her current position, and she jumped
on the opportunity.
When Lin joined the WPI-AIMR in
November 2008, she knew almost no-one.
But the turning point arrived four months
later when the WPI-AIMR held a weeklong workshop. Lin had discussions withmany researchers and found three eager
collaborators from the Bulk Metallic
Glasses Group — Na Chen, Deng Pan andDmitri Louzguine. In April 2009, theysubmitted a proposal for a fusion research
project and launched a project aimed atapplying bulk metallic glasses (BMGs) for
MEMS device fabrication.
Applying metallic glasses for MEMS
MEMS devices are micrometer-sized
sensors or actuators having electrical and

14© 2010 Tohoku University

Na Chen, research associate, Bulk Metallic Glasses Groupmechanical elements mounted on a single
board, and have origins in semiconductor
technology with key emphases onmaterials, fabrication and device design.
Historically, every introduction of an
innovative material, such as polymers,
silicon carbide, piezoelectrics and carbon
nanotubes, has become a landmark eventin the creation of a new realm of MEMS
applications. “We believe now is the time
for metallic glasses,” says Chen, a research
associate, citing BMG’s unusual strengthand formability.
When using conventional materials,
lithography is employed to transfer
patterns for MEMS devices. In addition
to conventional fabrication techniques,
however, the high formability anddurability of metallic glasses could
potentially allow such microscale parts toinstead be cast using a mold, considerably
simplifying the fabrication process. Thereis strong demand for a new MEMS
fabrication scheme, but BMGs have been
largely overlooked by engineers for use as
MEMS parts. Lin’s team is now developing
MEMS-compatible micro/nanofabrication methods for metallic glasses
and investigating how to integrate BMG

YOUNG RESEARCHERS

Taro Hitosugi, associate professor, Nanophysics Group

molding structures into MEMS devices.
But s u b s t ant ive te ch n ol o g i c a lchallenges lie ahead, as metallic glasses
have residual stress and poor adhesion
to the silicon and silicon oxide used incomplementary technologies. The teamhas tested a number of BMGs, and has
found that parameters such as pressure
and temperature are very important in
the fabrication process. “By combining
optimization of fabrication parametersand good selection of suitable BMG
materials, we believe we can solve thisbottleneck,” Lin says. Lin is also involvedin another fusion research project formedby four principal investigators to examine
the use of BMG as a novel bonding
material for MEMS bonding technology.
“Young people like me can be at thecenter of even ‘PI-level’ fusion research.
That is really encouraging,” say Lin.
Making the most of the WPI-AIMR
The WPI-AIMR philosophy has also
attracted young Japanese scientists likeTaro Hitosugi. When appointed as an
associate professor of the Nanophysics
Group, he was impressed with theinstitute’s generous support for theconstruction of an ideal laboratory at
his own discretion. As a researcher ofsurface and interface physics, his work
relies heavily on scanning tunnelingmicroscopy (STM), which is extremely
sensitive to noise and vibration. To shield
his instruments from such interference,
Hitosugi was allowed to cut out thelaboratory floor, drill piles down into
the bedrock, and pour 80 metric tons ofconcrete. The chamber is shielded with

Daisuke Hojo, assistant professor, NanoChemBio Group

special double walls, each of which is
40 cm thick; but the combined effect isequivalent to 10 meters of concrete, says
Hitosugi. “We have the best laboratory
for STM in Japan, and the lab is one of
the best in the world,” he says. “I’d liketo take advantage of the WPI-AIMR asmuch as possible.”
Like the weekly Tea Time, Hitosugi
finds that fascinating projects areof ten conceived t hroug h casualinteractions with Japanese and overseas
colleagues. One day in 2009, Hitosugi
dropped by the laboratory of Tadafumi
Adschiri, principal investigator of the
NanoChemBio Group and a specialistof novel nanostructural synthesis
technologies. As their conversation
developed from one topic to another, anidea for possible fusion research came up
and Hitosugi was introduced to Daisuke
Hojo, an assistant professor of the
Adschiri laboratory.

Shigemi Mizukami, assistant professor, Device/System GroupOne aspect of Hitosugi’s research is to
produce nanoscale thin oxide films thatshow interesting physical properties suchas superconductivity, and to investigate
their electronic structures and functionsat interfaces using STM. Hojo, on theother hand, synthesizes nanoparticles
of metal oxides and bonds them withorganic molecules in supercriticalwater. Usually, nanoparticles easily stick
together, but Hojo’s synthesis allows
nanoparticles to be dispersed uniformly
in a solvent, making them easier tohandle. These two researchers thought ofcombining their ‘dry’ and ‘wet’ processes
to create innovative nanoparticles that
acquire an anisotropic hetero-interface,which is impossible to achieve using wet
processes only. “This is an unusual idea,
but we can pursue maverick research
here,” Hojo says. The new product could
contribute to improve the properties ofnanoparticles in applications such as
semiconductors and catalysts, he adds.
A different fusion research project isunderway between Hitosugi and Shigemi
Mizukami, an assistant professor

Marco Haubold, GI3 laboratory student, Device/System Group

specialized in spintronics — electronics
utilizing the spin of electrons — in the
Device/System Group. Their projectis ambitiously aimed at changing themagnetic properties of a rechargeable
battery by controlling lithium ionsinstead of electrons as in conventional
systems. “I didn’t know ions behave
so interestingly. We could change
the paradigm of the battery system,”
Mizukami says. The lithium-ion batteries
in electric vehicles currently take about
five hours to recharge. If the interaction
between lithium-ion-diffusion andm a g n e t i s m c an b e s u c c e s s f u l ly
controlled, however, lithium-ion
batteries could be recharged much fasterby applying a magnetic field to control
the lithium ions.
Enhanced breadth as a researcher
The WPI-AIMR is not only generating
spontaneous collaborations but also
prompting young foreign talents to join
the institute thanks in part to an incentive
called the ‘Global Intellectual Incubation
and Integration Laboratory Project’,dubbed ‘GI3’. Marco Haubold, a studentof the Chemnitz University of Technology
in Germany, spent five months at the
WPI-AIMR to finish his diploma thesis.
Like Lin, he primarily studied thetheoretical aspects of MEMS materials,
so he wanted to gain some experimental
experience as well as discover the essenceof interdisciplinary research. “After one
month, I realized it would be very hard to
take the responsibility for both theoreticaland practical investigation,” Haubold
says. “But that’s the challenge I wanted,
and I am now feeling more competent.”
Haubold returned to Germany inDecember, but another student Frank
Roscher has recently arrived — also from
Germany — with the intent of enhancing
his breadth of vision to become a moreable materials researcher. “In addition to
the superb research environment at the
WPI-AIMR, Sendai is a very comfortable
place for research and living. Yes, I’d like tocome back again,” Haubold adds.

15© 2010 Tohoku University

YOUNG RESEARCHERS

INTERNATIONAL WORKSHOP

Bulk metallic glasses, France 2009
In August 2009, Tohoku University’s WPI-AIMR hosted an international workshop on bulk metallic glasses in Grenoble,
France. Attended by 70 researchers from 20 countries, the workshop was a great success thanks to facilitation by Alain
Reza Yavari, a professor of the Institut Polytechnique de Grenoble and a principal investigator at the WPI-AIMR.

In August, Tohoku University’s Advanced Institute for Materials

Understanding of the mechanical properties is the basis of all

Research hosted an international workshop on bulk metallic

applications of BMGs, and elucidation of shear band phenomena

glasses (BMGs) at the Maison du Tourism in Grenoble, France.

is key. In the past, the primary feature of single-crystal silicon

The workshop, attended by 70 researchers from 20 countries, was afor semiconductors was dislocation: for BMGs, it is shear bands.

great success thanks to facilitation by Alain Reza Yavari, a professor

To enhance the degree of freedom for processing, it is desirableof the Institut Polytechnique de Grenoble who concurrently holds

to enhance the temperature range of supercooling just before

the position of principal investigator at the WPI-AIMR.

vitrification, that is, to freely control the glass-transition point. To

The topics of the 52 oral presentations and 13 posters varied
from basic research to application with a focus on the mechanicalthis end, the number of elements forming high-quality BMGs andthe elemental ratio are important factors.

properties of BMGs. Many researchers reported their attempts

Researchers are making progress in discovering the compositions

to unveil the origin of BMG’s strengths compared to crystals.

that form BMGs and unveiling the guiding principle. Starting fromThe central topic was the ‘shear bands’ that arise when a BMG is

the eutectic phase diagram of three elements, and using the atomic

subject to plastic deformation. Individual presentations included

radius and electro-negativity as guides, participants in the discussions

the analysis of atomic bonding using synchrotron diffraction,

consolidated their ideas by sharing their experiments results.

observation of BMGs by scanning electron microscopy, andAt the end of the workshop, Yavari moderated comprehensive

simulations of atomic bonding in BMGs. In particular, there

discussions by all the participants. Akihisa Inoue, president of

were active discussions on cooperative phenomena, such as

Tohoku University, took part in the discussions and outlined

shear transformation zones and microscopic formation of shear

the WPI-AIMR’s objectives and organizational structure. Inouebands in BMGs.

reminded participants to be mindful of the critical evaluation ofhigh-quality research results, interdisciplinary or ‘fusion’ research,

Tunisia UK
Switzerland
1 1
Russia4
Romania2
Poland11
Korea 1USA

4

Australia

Brazil
China

1 1 3

and the application of research outcomes by the WPI-AIMR, while
expressing his resolve to make WPI-AIMR more global and attract

Colombia

1

France15

a greater number of distinctive young researchers.
The University of Cambridge professor A. L. Greer pointed outthat sustainability will be an important concept when proceedingwith applications. He added that BMGs could be applied for

520

maintaining the environment, for clean air and water and energy-

2
1 1 1

saving technologies using BMGs in magnetic applications,
GermanyJapan
Ireland

Iran
Italy

medicine and micro-devices.

GreeceAugust 29, 2009

The 2009 BMG workshop was attended by 70 participants from 20 countries

In Grenoble, Hiroshi Komatsu, professor emeritus of Tohoku University

16© 2010 Tohoku University

NEWS

WPI-AIMR director scoops RSC Centenary Prize
Yoshinori Yamamoto, institute directorof the WPI-AIMR, was selected as
one of the recipients of the 2009 RSC
Centenary Prize by the Royal Societyof Chemistr y (RSC), the foremost
organization for chemists in the United
Kingdom. Yamamoto, who pronounced
himself “surprised and delighted” atwinning the award, is only the seventh
Japanese -born researcher to behonored in this way.
The award, which was made inrecognition of Yamamoto’s “innovative
contributions to methodology inorganic synthesis” and comes with a
specially minted medal and a £5,000
prize, was presented at a ceremony inBirmingham, UK in November 2009.
The award also provides for the winners
to undertake a lecture tour of leading

academic institutions in the UK, which
subsequently saw Yamamoto visiting
York University, Queen’s University
Belfast and Durham University.
Fo r m e r l y t h e R S C C e n t e n a r y
Lectureship, the Centenary Prize wasinaugurated in 1947 to commemorate
the centenary of the Chemical Society,one of the forerunner institutions
that make up the RSC, and is awarded
annually to three researchers fromoutside the UK for outstanding
contributions to the chemical sciences.
The RSC Centenary Prize is one of themost prestigious awards given by
the UK chemical community and its
list of previous recipients resembles
a chemistry Hall of Fame with suchlegendary ﬁgures as Henry Taube, JeanMarie Lehn, R. Bruce Merriﬁeld and E. O.

Fischer among the ranks of awardees.
The 156 winners of the Centenary Prize
to date include 31 Nobel laureates,
among them Herbert C. Brown, who
was honored with the RSC Centenary
Lectureship in 1955 and who wasmentor to Yamamoto when the latter
was a postdoctoral researcher at Purdue
University from 1970 to 1972.

WPI-AIMR group leader honored byAmerican Physical Society(JSAP) with the ninth JSAP Outstanding

will lead to discoveries that will maintain

Achievement Award for “pioneering

Japan’s position as a leading manufacturer

Terunobu Miyazaki, group leader of the WPI-

research on room-temperature tunnelof integrated circuit technology for cellular

AIMR Device/System Group, was awarded

magneto-resistive devices.” Miyazaki, aphones and other related devices.

the 2009 Oliver E. Buckley Condensed

professor at the WPI-AIMR since November

Matter Prize for “pioneering work in the ﬁeld

2007, is involved in work centering onof spin-dependent tunneling and for thethe investigation of magnetism andapplication of these phenomena to the ﬁeld

magnetic materials. He is currently aof magnetoelectronics” by the American

member of the Spintronics Nonvolatile

Physical Society (APS). Miyazaki shared

Device Project funded by the New Energy

the award with three researchers from theand Industrial Technology Development

Massachusetts Institute of Technology.

Organization of Japan.

The ceremony was held on March 16, 2009
in Pittsburgh, Pennsylvania, USA where a

A boost for integrated microsystems

prize of US$10,000 and certificates were

The work of WPI-AIMR principal investigator2010 WPI-AIMR Annual Workshop

presented to the recipients by then APS

Masayoshi Esashi received a sizeable boost

25–27 March 2010

President Cherry A. Murray.

when he was chosen as a leading researcher

Tohoku University, Sendai, JapanThe Buckley Prize has been presented

in the “Funding Program for World-Leading

annually to outstanding researchers by

Innovative R&D on Science and Technology”

Following on from the highly

the APS since 1953 to recognize importantin July 2009. The funding, part of a multi-

successful 2009 workshop, thiscontributions to the advancement ofbillion dollar fund administered by theevent will discuss a range of current

knowledge in condensed matter physics.

Japan Society for the Promotion of Science,

topics in materials science including

Previous recipients of the award include

is intended to support the development ofbulk metallic glasses, nanophysics,

Nobel prize winners William Shockley, John

key technologies of international importancenanochembio and device/systems. The

Bardeen and Ivar Giaever as well as others.

over 3–5 years and comes from the Japanese

workshop will also include a number

government’s fiscal stimulus packageof parallel and plenary sessions as

announced in early 2009.

well as a poster session for younger

Last year was a very rewarding one
for Miyazaki, who was also recognizedby the Japan Society of Applied Physics

Easahi’s work is based on nano -researchers. Invited plenary speakers

technology and heterogeneous integration

include Zhaomin Hou (RIKEN), Akihisa

aimed at the development of cost-eﬀective

Inoue (Tohoku), Kohzo Ito (Tokyo), Jörg

and ﬂexible technologies for semiconductor

F. Löﬄer (ETH), Yoshio Nishi (Stanford),

integrated circuits. These technologies are

H. Eugene Stanley (Boston) and Jing

required by industry for the development

Zhu (Tsinghua).

and manufacturing of advanced electronic
devices. It is anticipated that the research

Further details are available from:carried out with the support of this grantwww.wpi-aimr.tohoku.ac.jp/workshop/

17© 2010 Tohoku University

Advanced Institute for Materials Research
Tohoku University

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