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Search Publications by: Thomas J. Silva (Fed)

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Displaying 76 - 100 of 135

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)

Limits of Storage in Magnetic Materials

December 31, 2004
Author(s)
Thomas J. Silva
I summarize what is currently known about how thermal effects limit the storage capacity of magnetic disk drives. The physics of thermal fluctuations in magnetic materials is treated in some detail, though the essential points are covered in a tutorial

Spin transfer switching of spin valve nanopillars using nanosecond pulsed currents

October 29, 2004
Author(s)
Shehzaad F. Kaka, Matthew Pufall, William Rippard, Thomas J. Silva, Stephen E. Russek, Jordan A. Katine, Matt Carey
Spin valve nanopillars are reversed via the mechanism of spin momentum transfer using current pulses applied perpendicular to the film plane of the device. The applied pulses were varied in amplitude from 1.8 to 7.8 mA, and varied in duration within the

Dynamic and static magnetic anisotropy in thin-film cobalt zirconium tantalum

October 26, 2004
Author(s)
John P. Nibarger, R Ewasko, Michael Schneider, Thomas J. Silva
The magnetic anisotropy values of thin amorphous cobalt zirconium tantalum (CZT) films were determined from static and dynamic measurements. Dynamic techniques show a rotatable component of anisotropy that decreases with increasing longitudinal bias field

Large-angle, gigahertz-rate random telegraph switching induced by spin-momentum transfer

July 27, 2004
Author(s)
Matthew Pufall, William Rippard, Shehzaad F. Kaka, Stephen E. Russek, Thomas J. Silva, Jordan A. Katine, Matt Carey
We show that a spin-polarized dc current passing through a small magnetic element induces two-state, random telegraph switching of the magnetization via the spin-momentum transfer effect. The resistances of the states differ by up to 50% of the change due

Finite coplanar waveguide width effects in pulsed inductive microwave magnetometry

July 12, 2004
Author(s)
Michael Schneider, Anthony B. Kos, Thomas J. Silva
The effect of finite coplanar waveguide (CPW) width on the measurement of the resonance frequency in thin ferromagnetic films has been characterized for pulsed inductive microwave magnetometry. A shift in resonant frequency is a linear function of the

Direct-Current Induced Dynamics in Co 90 Fe 10 /Ni 80 Fe 20 Point Contacts

January 16, 2004
Author(s)
William Rippard, Matthew Pufall, Shehzaad F. Kaka, Stephen E. Russek, Thomas J. Silva
We have directly measured coherent high-frequency magnetization dynamics in ferromagnetic films induced by a spin-polarized dc current. The precision frequency can be tuned over a range of several gigahertz by varying the applied current. The frequencies

High-Frequency Characteristics of Metal/Native-Oxide Multilayers

September 5, 2003
Author(s)
Geoffrey S. Beach, Thomas J. Silva, F. T. Parker, A. E. Berkowitz
The high-frequency magnetization dynamics of magnetically soft Co χFe 100-χ metal/native-oxide multilayers were studied as a function of alloy composition (10 less than or equal to} χ less than or equal to} 50) using a time-domain inductive technique. The