Magnetic Nanostructures for 

post-CMOS Electronics N

Our goal is to address the metrology of magnetic effects at the nanoscale 

level. Nanomagnet arrays form the basis for important data storage 

ANOMATERIALS

technologies, notably magnetoresistive random access memory and 

bit-patterned media for ultra-high density storage devices. Moreover, 

the semiconductor industry is looking beyond conventional CMOS 

processing, where current lithography techniques are expected to fail. 

Although fabrication methods for post-CMOS circuitry have not been 

established, it is certain that the magnetic components involved will be 

in the nanometer range. Even though defects are expected to dominate 

device behavior at this range, the metrology of defect-induced magnetic 

effects is not available at this scale.

Objective

Impact and Customers

• Magnetoresistive Random Access Memory (MRAM)

 MRAM chips are fast and energy efficient. However, a broader market 

for MRAM is hampered by nonuniformity issues resulting from the current 

manufacturing processes. Our research will address such limitations.

• Bit-patterned media hard drives

 Bit-patterned media is the future of ultrahigh density storage. Our 

research focuses on bit uniformity metrology to enable the identification 

and quantification of manufacturing problems that limit the deployment 

of this new platform in next generation hard drives.

• Post-CMOS electronics

 Our metrology will underpin the manufacturability of nascent devices 

using spin-based technologies. The incorporation of nanomagnets is 

desirable due to their high speed and low power consumption attributes, 

thus alleviating heat dissipation problems associated with CMOS 

scaling. 

Approach

Materials Science and Engineering Laboratory

We focus primarily on arrays of magnetic nanostructures in order to reveal how defects alter the fundamental 

physics of magnetization reversal processes in the nanometer regime. We have an integrated approach that consists 

of four interrelated elements. The first element, film edge metrology, 

addresses the role of the edge on magnetic behavior uniformity 

in magnetic nanostructures. The second element, magnetooptical 

nanostructure spectroscopy, is meant to provide fast and precise 

individual nanostructure “fingerprints”. Another element, microscopy, 

provides quantitative microstructure and defect information that can be 

correlated with magnetic behavior. Finally, a nanomagnetic modeling 

element offers an efficient and accurate theoretical predictive tool.

855-11-11b
Materials Science and Engineering Laboratory

Microstructural origin of switching 

field distribution 

We found an important microstructural 

origin of switching field distribution (SFD) 

in polycrystalline Co/Pd nanodot arrays. 

Based on the evidence that grains with inplane [100] vectors are correlated to dots 

with small switching fields, we concluded 

that these grains “trigger” or initiate 

switching.

Furthermore, the ease of switching these 

nanodots is linked to the size of the trigger 

grains. The extent to which the [001] vector 

points out of plane may also play a role 

in reducing the switching field. Control of 

the microstructure, to eliminate the trigger 

grain, may be the key to reducing the SFD 

in Co/Pd nanodot arrays.

Thin film edge magnetic properties 

vary with patterning process 

conditions 

Using ferromagnetic resonance 

spectroscopy, we were able to separate 

edge behavior from bulk behavior in 

Permalloy magnetic nanostripes. We 

showed that the patterned edges of 

magnetic films have measurable magnetic 

characteristics, and that quantitatively, the 

magnetic properties depend on the etching 

conditions used to create the edges. These 

results have important implications for 

generating nanostructure arrays with 

uniform properties and for understanding 

the behavior of magnetic nanodevices. 

Modeling polycrystallinity in 

nanomagnets

In response to the growing need for a 

more accurate micromagnetic model to 

understand switching phenomenon in 

nanoscale magnets, we developed the 

capability to model magnetic behavior 

due to polycrystalline grains using the 

NIST Object Oriented Micromagnetic 

Framework (OOMMF). This allows users 

full flexibility in determining the easy 

axis orientations and magnetocrystalline 

anisotropy in each individual grain, as well 

as the intergranular exchange coupling 

strength. 

Micromagnetics on curved 

geometries using rectangular cells

We introduced a 3-D compatible 

correction method for calculating the 

micromagnetics of arbitrary shaped 

magnetic elements using regular finitedifference discretization. The correction 

reuses the magnetostatic code on a finer 

mesh to compute local anisotropy terms for 

cells in the neighborhood of the boundary. 

To validate the correction algorithm, we 

used an edge mode frequency test, which 

revealed that grid-induced magnetic 

behaviors were largely eliminated. 

Accomplishments

Robert McMichael (CNST)

Thomas Silva (EEEL)

Justin Shaw (EEEL)

Michael Donahue (ITL)

June W. Lau

(Metallurgy)

(301) 975-5711

june.lau@nist.gov

www.nist.gov/metallurgy

Learn More Publications

Trigger grain causes SFD in Co/Pd nanodots

Modeling nanograins as a magnetization

reversal trigger

Lau JW, McMichael RD, Schofield MA and Zhu Y Correlation of Edge Roughness to Nucleation 

Field and Nucleation Field Distribution in Patterned Permalloy Elements J. Appl. Phys., 102: 

023916 (2007)

Lau JW, McMichael RD, Chung SH, Rantschler JO, Parekh V and Litvinov D Microstructural 

Origin of Switching Field Distribution in Patterned Co/Pd Multilayer Nanodots Appl. Phys. 

Lett., 92: 012506 (2008)

Maranville BB, McMichael RD and Abraham DW Variation of Thin Film Edge Magnetic 

Properties with Patterning Process Conditions in Ni80Fe20 Stripes Appl. Phys. Lett., 90: 232504 

(2007)

Donahue MJ and McMichael RD Micromagnetics on Curved Geometries Using Rectangular 

Cells: Error Correction and Analysis IEEE Transactions on Magnetics, 43: 2878 (2007)

Measured resonances in nano-stripes

Edge modes test the robustness of correction