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Search Publications by: Thomas J. Silva (Fed)

Displaying 176 - 200 of 270

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

Current-Driven Microwave Dynamics in Magnetic Point Contacts as a Function of Applied Field Angle

December 1, 2004

Author(s)

William Rippard, Matthew Pufall, Shehzaad F. Kaka, Thomas J. Silva, Stephen E. Russek

We have measured microwave frequency, current-driven magnetization dynamics in point contacts made to Co 90Fe 10/Cu/Ni 80Fe 20 spin valves as a function of applied field strength and angle relative to the film plane. As the field direction is varied from

Large-angle magnetization dynamics investigated by vector-resolved magnetization-induced optical second-harmonic generation

December 1, 2004

Author(s)

Thomas Gerrits, Thomas J. Silva, John P. Nibarger, Theo Rasing

We examine the relationship between nonlinear magnetic responses and the change in the Gilbert damping parameter α for patterned and unpatterned thin Permalloy films when subjected to pulsed magnetic fields. An improved magnetization-vector-resolved

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

Materials dependence of the spin-momentum transfer efficiency and critical current in ferromagnetic metal/Cu multilayers

July 14, 2003

Author(s)

Matthew Pufall, William Rippard, Thomas J. Silva

We have quantitatively compared spin momentum transfer effects in FM/Cu multilayers, with FM = Co, Co 90Fe 10, Ni 80Fe 20, Ni 40Fe 10Cu 50, and Fe. All of the measured multilayers exhibited an abrupt step in the resistance at a critical current I c, the

Variation of the effective magnetization and the Lande g factor with thickness in thin Permalloy films

July 7, 2003

Author(s)

John P. Nibarger, Radek Lopusnik, Thomas J. Silva, Zbigniew J. Celinski

We have simultaneously measured the Lande g factor, the effective magnetization, M eff, and the uniaxial anisotropy, H k, and the Gilbert damping parameter α, as a function of Permalloy film thickness from 2.5 to 50 nm. We used a pulsed inductive microwave