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Search Publications by: Thomas J. Silva (Fed)

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Displaying 51 - 75 of 135

Ultrafast Demagnetization Measurements using Extreme Ultraviolet Light: Comparison of Electronic and Magnetic Contributions

January 23, 2012
Author(s)
Thomas J. Silva, Justin M. Shaw, Hans T. Nembach, Margaret M. Murnane, Henry C. Kapteyn, Chan La-O-Vorakiat, Stefan Mathias, Emrah Turgut, Teale A. Carson, Martin Aeschlimann, Claus M. Schneider
Ultrashort pulses of extreme ultraviolet light from high-harmonic generation are a new tool for probing coupled charge, spin, and phonon dynamics with element specificity, attosecond pump-probe synchronization, and time resolution of a few-femtoseconds in

Perpendicular ferromagnetic resonance measurements of damping and Lande g-factor in sputtered (Co 2 Mn) 1-x Ge x thin films

August 8, 2011
Author(s)
Thomas J. Silva, Hans T. Nembach, Justin M. Shaw, Michael Schneider, Matt Carey, Stefan Maat, Jeff Childress
X-ray diffraction (XRD), magnetometry, and ferromagnetic resonance (FMR) measurements were performed on sputtered thin films of the nominal Heusler alloy (Co 2Mn) 1-xGe x with varying Ge content and annealing temperature. XRD indicates some degree of L2 1

Damping phenomena in Co 90 Fe 10 /Ni multilayers and alloys

July 6, 2011
Author(s)
Justin M. Shaw, Hans T. Nembach, Thomas J. Silva
We used perpendicular ferromagnetic resonance to measure the damping parameter in Co 90Fe 10/Ni multilayers over a wide range of layer thicknesses. The magnetic anisotropy within this range varied from in-pane to out-of-plane. We measured (Co 90Fe 10) xNi

Effects of shape distortions and imperfections on mode frequencies and collective linewidths in nanomagnets

March 28, 2011
Author(s)
Hans T. Nembach, Justin M. Shaw, Thomas J. Silva, Ward L. Johnson, Sudook A. Kim, Robert D. McMichael, Pavel Kabos
We used Brillouin light scattering to show that shape distortions in Ni80Fe20 nanoelements can have a dramatic effect on the measured linewidth of certain modes. By intentionally introducing an amount of “egg-like” shape distortion to an ideal elliptical

Intrinsic defects in perpendicularly magnetized multilayer thin films and nanostructures

October 26, 2010
Author(s)
Justin M. Shaw, Miles Olsen, June W. Lau, Michael L. Schneider, Thomas J. Silva, Olav Hellwig, Elizabeth Dobisz, Bruce D. Terris
Intrinsic magnetic defects in perpendicularly magnetized nanostructures reduce the predictability of device and developing recording technologies. In addition to a distribution of local anisotropy fields, we show that such defects also exhibit variations

Theory for a Dissipative Droplet Soliton Excited by a Spin Torque Nanocontact

August 30, 2010
Author(s)
Mark Hoefer, Thomas J. Silva, Mark W. Keller
A distinct type of solitary wave is predicted to form in spin torque oscillators when the free layer has a sufficiently large perpendicular anisotropy. In this structure, which is a dissipative version of the conservative droplet soliton originally studied

Ultrafast Demagnetization Dynamics at the M Edges of Magnetic Elements Observed Using a Tabletop High-Harmonic Soft X-Ray Source

December 15, 2009
Author(s)
Thomas J. Silva, Justin Shaw, Hans Nembach, Chan La-O-Vorakiat, Mark Siemens, Margaret M. Murnane, Henry C. Kapteyn, Stefan Mathias, Martin Aeschlimann, Patrik Grychtol, Roman Adam, Claus M. Schneider
We use few-femtosecond soft x-ray pulses from high-harmonic generation to extract element-specific demagnetization dynamics and hysteresis loops of a compound material for the first time. Using a geometry where high-harmonic beams are reflected from a

Temperature dependence of spin-torque-driven self-oscillators

October 15, 2009
Author(s)
William H. Rippard, Matthew R. Pufall, Thomas Cecil, Thomas J. Silva, Stephen E. Russek, M. L. Schneider
We have measured the temperature dependence of spin-torque-driven self-oscillations in point-contact nanooscillators for both in-plane and out-of-plane applied fields. We find that the linewidth for both field geometries is qualitatively similar. In the

Microwave assisted magnetization reversal in single domain nanoelements

July 6, 2009
Author(s)
Hans T. Nembach, Hans Bauer, Justin M. Shaw, Michael Schneider, Thomas J. Silva
We studied the microwave assisted magnetic reversal in 65×71 nm 2 elliptical Ni 80Fe 20 nanomagnets with a thickness of 10 nm. Hysteresis curves were measured by magneto-optical Kerr effect for a range of microwave frequencies and amplitudes. We observe a

Time domain measurement of phase noise in a spin torque oscillator

May 13, 2009
Author(s)
Mark W. Keller, Anthony B. Kos, Thomas J. Silva, William H. Rippard, Matthew R. Pufall
We measure phase noise from the zero crossings of the voltage vs. time waveform of a spin torque nanocontact oscillating in a vortex mode. The power spectrum of the phase noise varies with Fourier frequency f as 1/f 2, consistent with frequency

Collimated spin wave beam generated by a single layer, spin torque nanocontact

April 1, 2008
Author(s)
Mark Hoefer, Thomas J. Silva, M D. Stiles
A model of spin-torque-induced magnetization dynamics based on semiclassical spin diffusion theory for a single-layer nanocontact in presented. The model incorporates effects due to the current-induced Oersted field and predicts the generation of a variety

Developments in nano-oscillators based upon spin-transfer point-contact devices

December 31, 2007
Author(s)
Thomas J. Silva, William H. Rippard
We review the current status of research on microwave nano-oscillators that utilize spin transfer devices with point-contact geometry, with an emphasis on the open questions that still prevent our full understanding of device properties. In particular, we

Experimental determination of the inhomogeneous contribution to linewidth in Permalloy films using a time-resolved magneto-optic Kerr effect microprobe

September 12, 2007
Author(s)
Michael Schneider, Thomas Gerrits, Anthony B. Kos, Thomas J. Silva
We adapted a time-resolved magneto-optic microprobe for use with the pulsed inductive microwave magnetometer apparatus, allowing us to measure the magnetization dynamics of a thin Permalloy film at micrometer and millimeter length scales under exactly the

Field-free ringing of nanomagnets

July 1, 2007
Author(s)
Thomas J. Silva
Ever since William Gilbert's 16th century treatise "De Magnete," it has been known that magnetic fields can be used to manipulate the magnetic orientation of ferromagnets. This has been the foundation for electronic applications of magnetic materials for

Spin Torque for Dummies

January 6, 2007
Author(s)
Thomas J. Silva
I will present a stripped down presentation on the fundamental mechanisms that give rise to spin torque effects. This presentation will assume the audience has little or no background in this fascinating and rapidly expanding field. We will start with an