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papers

Publications (16)

cond-mat.mes-hall2012

Switching Distributions for Perpendicular Spin-Torque Devices within the Macrospin Approximation

W. H. Butler, T. Mewes, C. K. A. Mewes +4

We model "soft" error rates for writing (WSER) and for reading (RSER) for perpendicular spin-torque memory devices by solving the Fokker-Planck equation for the probability distrib…

cond-mat.mtrl-sci2004

Monte Carlo simulation of equilibrium L1_0 ordering in FePt nanoparticles

R. V. Chepulskii, J. Velev, W. H. Butler

First, second and third nearest neighbor mixing potentials for FePt alloys, were calculated from first principles using a Connolly-Williams approach. Using the mixing potentials ob…

cond-mat.mtrl-sci2004

Large magnetoresistance in bcc Co/MgO/Co and FeCo/MgO/FeCo tunneling junctions

X. -G. Zhang, W. H. Butler

By use of first-principles electronic structure calculations, we predict that the magnetoresistance of the bcc Co(100)/MgO(100)/bcc Co(100) and FeCo(100)/MgO(100)/FeCo(100) tunneli…

cond-mat.mtrl-sci2011

Effects of 3-d and 4-d-transition metal substitutional impurities on the electronic properties of CrO2

M. E. Williams, H. Sims, D. Mazumdar +1

We present first-principles based density functional theory calculations of the electronic and magnetic structure of CrO2 with 3d (Ti through Cu) and 4d (Zr through Ag) substitutio…

cond-mat.mes-hall2015

Analytical description of ballistic spin currents and torques in magnetic tunnel junctions

M. Chshiev, A. Manchon, A. Kalitsov +5

In this work we demonstrate explicit analytical expressions for both charge and spin currents which constitute the 2x2 spinor in magnetic tunnel junctions with noncollinear magneti…

cond-mat.mtrl-sci2005

Spin Dependent Tunneling in FM|semiconductor|FM structures

S. Vutukuri, M. Chshiev, W. H. Butler

Here we show that ordinary band structure codes can be used to understand the mechanisms of coherent spin-injection at interfaces between ferromagnets and semiconductors. This appr…

cond-mat.mtrl-sci2012

Theoretical investigation into the possibility of very large moments in Fe16N2

H. Sims, W. H. Butler, M. Richter +4

We examine the mystery of the disputed high-magnetization Î±"-Fe16N2 phase, employing the Heyd-Scuseria-Ernzerhof screened hybrid functional method, perturbative many-body correcti…

cond-mat.stat-mech2007

Domain wall switching: optimizing the energy landscape

Zhihong Lu, P. B. Visscher, W. H. Butler

It has recently been suggested that exchange spring media offer a way to increase media density without causing thermal instability (superparamagnetism), by using a hard and a soft…

cond-mat.mtrl-sci2008

Voltage Dependence of Spin Transfer Torque in Magnetic Tunnel Junctions

M. Chshiev, I. Theodonis, A. Kalitsov +2

Theoretical investigations of spin transfer torque in magnetic tunnel junctions using the tight-binding model in the framework of non-equilibrium Green functions formalism are pres…

cond-mat.mtrl-sci2013

Determining the Anisotropic Exchange Coupling of CrO_2 via First-Principles Density Functional Theory Calculations

H. Sims, S. J. Oset, W. H. Butler +2

We report a study of the anisotropic exchange interactions in bulk CrO_2 calculated from first principles within density functional theory. We determine the exchange coupling energ…

cond-mat.mtrl-sci2008

Half-Metallic L2 $_{1}$ Structures with (001) Planar Insertions

C. A. Culbert, M. Williams, M. Chshiev +1

A number of L2 $_{1}$ phase alloys (composition X $_{2}$ YZ) are half-metallic. Although this structure is typically described in terms of an fcc Bravais lattice with a 4 atom basis, it c…

cond-mat.mtrl-sci2025

Tailoring properties of Heusler alloys by elemental substitution and electron counting: (Co $_{2 - I^\pm}$ Mn $_{I^} \pm$ )FeGe, Co $_{2}$ (Fe $_{1 - I^^{2}}$ Mn $_{I^}^{2}$ )Ge, and (Co $_{2 - I^\pm}$ Fe $_{I^} \pm$ )MnGe

R. Mahat, S. Budhathoki, S. Regmi +6

Rational material design by elemental substitution is useful in tailoring materials to have desirable properties. Here we consider three non-equivalent substitutional series based…

cond-mat.mtrl-sci2016

Computational Investigation of Half-Heusler Compounds for Spintronics Applications

Jianhua Ma, Vinay I. Hegde, Kamaram Munira +6

We present first-principles density functional calculations of the electronic structure, magnetism, and structural stability of 378 $XYZ$ half-Heusler compounds (with $X =$ …

cond-mat.mes-hall2009

Surface segregation in nanoparticles from first principles

Roman V. Chepulskii, W. H. Butler, A. van de Walle +1

FePt nanoparticles are known to exhibit reduced L1 $_{0}$ order with decreasing particle size. The reduction in order reduces the magnetic anisotropy and the thermal stability of the…

cond-mat.mtrl-sci2005

Temperature and particle size dependence of equilibrium order parameter of FePt

R. V. Chepulskii, W. H. Butler

First, second and third nearest neighbor pair mixing potentials for equiatomic FePt alloys were calculated from first principles by the Connolly-Williams method within the canonica…

cond-mat.other2005

Spin-Polarized Current Induced Torque in Magnetic Tunnel Junctions

A. Kalitsov, I. Theodonis, N. Kioussis +3

We present tight-binding calculations of the spin torque in non-collinear magnetic tunnel junctions based on the non-equilibrium Green functions approach. We have calculated the sp…