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Search Publications by: Mark D. Stiles (Fed)

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Displaying 101 - 125 of 201

A Numerical Method to Solve the Boltzmann Equation for a Spin Valve

October 1, 2007
Author(s)
J Xiao, A Zangwill, Mark D. Stiles
We present a numerical algorithm to solve the Boltzmann equation for the electron distribution function in magnetic multilayer heterostructures with non-collinear magnetizations. The solution is based on a scattering matrix formalism for layers that are

Theory of Spin Transfer Torque

September 1, 2007
Author(s)
Mark D. Stiles
In magnetic multilayers, the spin polarized currents flowing between the magnetic layers can exert torques on the magnetizations of the layers when the magnetizations are not collinear. The theory of these spin transfer torques is developed in terms of

Adiabatic Domain Wall Motion and Landau-Lifshitz Damping

January 1, 2007
Author(s)
Mark D. Stiles, Wayne M. Saslow, Michael J. Donahue, A Zangwill
Recent theory and measurements of the velocity of current-driven domain walls in magnetic nanowires have re-opened the unresolved question of whether Landau-Lifshitz damping or Gilbert damping provides the more natural description of dissipative

Spin-Orbit Precession Damping in Transition Metal Ferromagnets

January 1, 2007
Author(s)
Keith Gilmore, Y Idzerda, Mark D. Stiles
We provide a simple explanation, based on an effective field, for the precession damping rate due to the spin-orbit interaction. Previous effective field treatments of spin-orbit damping include only variations of the state energies with respect to the

Two Simple Tests for Models of Current-Induced Magnetization Switching

January 1, 2007
Author(s)
N Theodoropoulou, Abhishek Sharma, W Pratt, Mark D. Stiles, J Xiao, J Bass
We describe two simple tests for models of current-induced magnetization switching due to spin-transfer-torque in ferromagnetic/non-magnetic/ferromagnetic (F/N/F) trilayers. The first involves comparing calculated and measured values of the ratio X = ?I(Cu

Spin Transfer Torque and Dynamics

November 1, 2006
Author(s)
Mark D. Stiles, J Miltat
The currents in magnetic multilayers are spin polarized and carry enough angular momentum that they can cause magnetic reversal and induce stable precession of the magnetization in thin magnetic layers. The flow of spins is determined by the spin-dependent

Preoxidation as a general approach to suppressing orange-peel coupling in magnetic tunnel junctions

October 1, 2006
Author(s)
William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell
We have found that preoxidation of the bottom electrode prior to deposition of Al 2O 3 or MgO is very effective as a general approach to suppressing orange-peel coupling in magnetic tunnel junctions. When orange-peel coupling is suppressed, the hard-axis

Soft magnetic layers for low-field-detection magnetic sensors

May 18, 2006
Author(s)
William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Freemon Johnson, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell
We have investigated a wide variety of soft magnetic layers as sense layers for magnetic-field sensors. We find that in thin-film form, some of these soft materials can have susceptibilities (?) approaching those of the corresponding bulk material. In

Exchange Coupling in Magnetic Multilayers

May 1, 2006
Author(s)
Mark D. Stiles
In magnetic multilayers, the magnetizations of two ferromagnetic layers separated by a non-magnetic spacer layer are coupled by the electrons in the spacer layer. This coupling oscillates in sign as a function of the thickness of the spacer layer

Electronic Effects in Length Distribution of Atom Chains

April 17, 2006
Author(s)
Jason Crain, Mark D. Stiles, Joseph A. Stroscio, Daniel T. Pierce
Gold deposited on Si(553) leads to self assembly of atomic chains, which are broken into finite segments by atomic defects. Scanning tunneling microscopy is used to investigate the distribution of chain lengths and the correlation between defects

Suppression of Orange-Peel Coupling in Magnetic Tunnel Junctions by Preoxidation

April 17, 2006
Author(s)
William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell
We have found that preoxidation of the bottom Co electrode in magnetic tunnel junctions (MTJs) very effectively suppresses orange-peel coupling. The result is a free layer that is much softer. Work by others has demonstrated that preoxidation is compatible

Spin Transfer Torque for Continuously Variable Magnetization

February 21, 2006
Author(s)
J Xiao, A Zangwill, Mark D. Stiles
We report quantum and semi-classical calculations of spin current and spin-transfer torque in a free-electron Stoner model for systems where the magnetization varies continuously in one dimension. Analytic results are obtained for an infinite spin spiral

Spin Transport for Spin Diffusion Lengths Comparable to Mean Free Paths

December 15, 2005
Author(s)
David R. Penn, Mark D. Stiles
In perpendicular-transport structures with magnetic and non-magnetic layers, there is a resistance associated with changes in the value of current polarization throughout the structure. Starting from a Boltzmann equation Valet and Fert derived macroscopic

Macrospin Models of Spin Transfer Dynamics

July 1, 2005
Author(s)
J Xiao, A Zangwill, Mark D. Stiles
The current-induced magnetization dynamics of a spin valve are studied using a macrospin (single-domain) approximation and numerical solutions of a generalized Landau-Lifshitz-Gilbert equation. For the purpose of quantitative comparison to experiment [S. I

Current-induced switching in a single exchange-biased ferromagnetic layer

May 15, 2005
Author(s)
Tingyong Chen, Yi Ji, C Chien, Mark D. Stiles
We demonstrate current-induced switching effects in a single exchanged-biased ferromagnetic layer. A nanodomain can be switched within the ferromagnetic layer by a spin polarized current injected through a point contact. The high resistance of the

Magnetic normal modes of nano-elements

May 15, 2005
Author(s)
Robert McMichael, Mark D. Stiles
Micromagnetic calculations are used to determine the eigenfrequencies and precession patterns of some of the lowest-frequency magnetic normal modes of submicron patterned elements. For a Permalloy-like ellipse, 350 nm ¿ 160 nm ¿ 5 nm thick in zero field

Magnetic Normal Modes of Nanoelements

May 1, 2005
Author(s)
Robert D. McMichael, Mark D. Stiles
Micromagnetic calculations are used to determine the eigenfrequencies and precession patterns of some of the lowest-frequency magnetic normal modes of submicron patterned elements. For a Permalloy-like ellipse, 350 nm 160 nm 5 nm thick in zero field, the

Artifacts That Mimic Ballistic Magnetoresistance

February 1, 2005
Author(s)
William F. Egelhoff Jr., L Gan, H Ettedgui, Y Kadmon, Cedric J. Powell, P J. Chen, Alexander J. Shapiro, Robert McMichael, J Mallett, Thomas P. Moffat, Mark D. Stiles, Erik B. Svedberg
We have investigated the circumstances underlying recent reports of very large values of ballistic magntoresistance (BMR) in nanocontacts between magnetic wires. We find that the geometries used are subject to artifacts due to motion of the wires that

Interlayer Exchange Coupling

December 13, 2004
Author(s)
Mark D. Stiles
In magnetic multilayers, in which ferromagnetic layers are separated by non-magnetic spacer layers, the magnetizations are coupled by interactions across the spacer layer. One type of coupling, bilinear exchange coupling, originates from the quantum well

Boltzmann Test of Slonczewski's Theory of Spin Transfer Torque

November 12, 2004
Author(s)
J Xiao, A Zangwill, Mark D. Stiles
We use a matrix Boltzmann equation formalism to test the accuracy of Slonczewski's theory of spin-transfer torque in thin-film heterostructures where a non-magnetic spacer layer separates two non-collinear ferromagnetic layers connected to non-magnetic