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Search Publications by: Thomas J. Silva (Fed)

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Displaying 76 - 100 of 156

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

Ferromagnetic resonance linewidth in metallic thin films: Comparison of measurement methods

May 22, 2006
Author(s)
Sangita S. Kalarickal, Pavol Krivosik, Mingzhong Wu, C E. Patton, Michael Schneider, Pavel Kabos, Thomas J. Silva, John P. Nibarger
Strip line (SL), vector network analyzer (VNA), and pulsed inductive microwave magnetometer (PIMM) techniques were used to measure the ferromagnetic resonance (FMR) linewidth for a series of Permalloy films with thicknesses of 50 and 100 nm. The SL-FMR

Large-angle magnetization dynamics measured by time-resolved ferromagnetic resonance

March 30, 2006
Author(s)
Thomas Gerrits, Michael Schneider, Anthony B. Kos, Thomas J. Silva
A time-resolved ferromagnetic resonance technique was used to investigate the nonlinear magnetization dynamics of a 10 nm thin Permalloy TM film in response to a sequence of large-amplitude field pulses. The magnetic field pulse sequence was set at a

Surface oxidation of Permalloy thin films

January 24, 2006
Author(s)
M. R. Fitzsimmons, Thomas J. Silva, T. M. Crawford
The chemical and magnetic structures of oxides on the surface of Permalloy Ni 81Fe 19 films were investigated as functions of annealing time with x-ray and polarized neutron reflectometry. For annealing times of less than one hour, the oxide consisted of a

Enhanced ferromagnetic damping in Permalloy/Cu bilayers

January 18, 2006
Author(s)
Thomas Gerrits, Michael Schneider, Thomas J. Silva
We have investigated the enhancement of ferromagnetic damping for thin Permalloy (Ni 80Fe 20) films grown with Cu capping layers of variable thickness (5-1000nm). The measurements were performed with a pulsed inductive microwave magnetometer in the

Dependence of magnetization dynamics on magnetostriction in NiFe alloys

December 23, 2005
Author(s)
Roberto Bonin, Michael Schneider, Thomas J. Silva, John P. Nibarger
We present a quantitative, systematic study of the effect of magnetostriction on the dynamical properties in NiFe alloys. Both the ferromagnetic resonance frequency and the damping times are correlated to the magnetostriction. In addition, we find that the

Mutual phase-locking of microwave spin torque nano-oscillators

September 15, 2005
Author(s)
Shehzaad F. Kaka, Matthew Pufall, William Rippard, Thomas J. Silva, Stephen E. Russek, Jordan A. Katine
The spin torque effect that occurs in nanometre-scale magnetic multilayer devices can be used to generate steady- state microwave signals in response to a d.c. electrical current. This establishes a new functionality for magneto-electronic structures that

Injection Locking and Phase Control of Spin Transfer Nano-Oscillators

August 5, 2005
Author(s)
William Rippard, Matthew Pufall, Shehzaad F. Kaka, Thomas J. Silva, Stephen E. Russek, Jordan A. Katine
We have directly measured phase locking of spin transfer oscillators to an injected ac current. The oscillators lock to signals up to several hundred megahertz away from their natural oscillation frequencies, depending on the relative strength of the input

Pump-probe Faraday rotation magnetometer using two diode lasers

April 26, 2005
Author(s)
Forrest T. Charnock, Radek Lopusnik, Thomas J. Silva
A time-resolved Faraday rotation magnetometer using externally triggered pulsed diode lasers is described. This device permits measurement of the dynamic properties of polarized electronic spins in semiconductors. A non- equilibrium spin polarization is

Finite-temperature modeling of nanoscale spin-transfer oscillators

March 31, 2005
Author(s)
Stephen E. Russek, Shehzaad F. Kaka, William Rippard, Matthew Pufall, Thomas J. Silva
Magnetization dynamics induced by spin-polarized currents in magnetic nanodevices have been numerically simulated using a single-domain model proposed by Slonczewski extended to include temperature effects. For currents with a spin polarization

Frequency modulation of spin-transfer oscillators

February 18, 2005
Author(s)
Matthew Pufall, William Rippard, Shehzaad F. Kaka, Thomas J. Silva, Stephen E. Russek
Spin-polarized dc electric current flowing into a magnetic layer can induce precession of the magnetization at a frequency that depends on current. We show that addition of an ac current to this dc bias current results in a frequency modulated (FM)