Reversal of Spin Polarization in Fe/GaAs (001) Driven by Resonant Surface States: First-Principles Calculations

Athanasios Chantis, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico
Kirill Belashchenko, University of Nebraska - Lincoln
Darryl L. Smith, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico
Evgeny Tsymbal, University of Nebraska - Lincoln
Mark van Schilfgaarde, School of Materials, Arizona State University, Tempe, Arizona
Robert C. Albers, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico

Published in PRL 99, 196603 (2007). Copyright © 2007 The American Physical Society. Used by permission.

Abstract

A minority-spin resonant state at the Fe/GaAs(001) interface is predicted to reverse the spin polarization with the voltage bias of electrons transmitted across this interface. Using a Green’s function approach within the local spin-density approximation, we calculate the spin-dependent current in a Fe/GaAs/Cu tunnel junction as a function of the applied bias voltage. We find a change in sign of the spin polarization of tunneling electrons with bias voltage due to the interface minority-spin resonance. This result explains recent experimental data on spin injection in Fe/GaAs contacts and on tunneling magnetoresistance in Fe/GaAs/Fe magnetic tunnel junctions.