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# Nanoscale Spin Dynamics Group

The Nanoscale Spin Dynamics Group develops new measurement techniques to characterize the high frequency properties and performance of nanomagnetic structures and devices.

Hard-disk drives in personal computers and data centers push the limits of technology, with current data bit densities of 100 billion per square centimeter. The controlled switching of magnetization in write heads, read heads, recording media, and innovative memory elements at frequencies in the hundreds of megahertz to hundreds of gigahertz will be the foundation for future magnetic data storage systems and advanced microwave integrated circuits. These technologies will depend on newly discovered properties and limitations of magnetic materials and devices that appear only at the nanoscale.

We will develop coherent X-ray scattering techniques that will enable room-temperature detection and characterization of magnetic topological defects (skyrmions) at length scales as small as 5 nm. The new method will rely on optical generation of skyrmions via the Kibble-Zurek mechanism, whereby rapid cooling of a magnet through the Curie temperature after optical pumping will necessarily generate topological defects. Detection of skyrmions will rest on the distinct diffractive fingerprint of the scattered photons. Analysis of the diffraction pattern will be used to determine the skyrmion size and density. We will use both coherent X-ray and extreme ultraviolet laser facilities for these measurements, including those of our long-time collaborators at University of ColoradoCU/JILA. Results of these measurements will be crucial for the evaluation of materials as candidates for spintronics applications, including racetrack memory and logic-in-memory.

## News and Updates

### NIST System Replicated by Chip Maker

A highly sensitive measurement system for the performance of nanoscale magnetic devices, invented and developed at NIST

## Projects and Programs

### Spin Dynamics and Magnetic Microscopy

The Spin Dynamics and Magnetic Microscopy Project develops metrology for magnetodynamic effects such as ferromagnetic resonance, switching, and damping. We

### Spin Transport

The Spin Transport program performs basic and applied research, and develops new measurement capabilities, to enable the development of high-speed, nonvolatile

## Publications

### Near-Unity Spin Hall Ratio in Ni$_x$Cu$_{1-x}$ Alloys

Author(s)
Mark W. Keller, Katy Gerace, Monika Arora, Justin M. Shaw, Thomas J. Silva
We report a large spin Hall effect in the 3$d$ transition metal alloy Ni$_x$Cu$_{1-x}$ for $x \in \{ 0.3,0.75\}$, detected via the ferromagnetic resonance of a

### Magnetic damping in sputtered Co2MnGe Heusler compounds with A2, B2 and L21 order: Experiment and Theory

Author(s)
Justin M. Shaw, Eric R. Edwards, Martin A. Schoen, Michael L. Schneider, Matthew R. Pufall, Thomas J. Silva, Hans T. Nembach, Erna Delczeg
We show that very low values of the magnetic damping parameter can be achieved in sputter deposited poly-crystalline films of Co2MnGe annealed at relatively low

### Direct measurement of the static and 1 transient magneto-optical permittivity of cobalt across the entire M-edge in a reflection geometry by use of polarization scanning

Author(s)
Dmitriy Zusin, Phoebe Tengdin, Maithreyi Gopalakrishnan, Christian Gentry, Adam Blonsky, Michael Gerrity, Justin M. Shaw, Hans T. Nembach, Thomas J. Silva, Peter Oppeneer, Henry Kapteyn, Margaret Murnane

### Symmetry-broken dissipative exchange flows in thin-film ferromagnets with in-plane anisotropy with in-plane anisotropy

Author(s)
Ezio E. Iacocca, Thomas J. Silva, Mark Hoefer
Planar ferromagnetic channels have been shown to theoretically support a long-range ordered and coherently precessing state where the balance between local spin

## Awards

### 2016 IEEE Fellow - Thomas Silva

The IEEE Grade of Fellow is conferred by the IEEE Board of Directors upon a person with an outstanding record of accomplishments in any of...

### 2010 APS Fellow - Thomas Silva

The criterion for election is exceptional contributions to the physics enterprise; e.g., outstanding physics research, important...