Research Papers in Physics and Astronomy

 

Bias Voltage Dependence of Tunneling Anisotropic Magnetoresistance in Magnetic Tunnel Junctions with MgO and Al2O3 Tunnel Barriers

Li Gao, IBM Research Division, Almaden Research Center, San Jose, California
Xin Jiang, IBM Research Division, Almaden Research Center, San Jose, California
See-Hun Yang, IBM Research Division, Almaden Research Center, San Jose, California
John Burton, University of Nebraska - Lincoln
Evgeny Tsymbal, University of Nebraska - Lincoln
Stuart S. P. Parkin, IBM Research Division, Almaden Research Center, San Jose, California

Published in PRL 99, 226602 (2007). Copyright © 2007 The American Physical Society. Used by permission.

Abstract

Tunneling anisotropic magnetoresistance (TAMR) is observed in tunnel junctions with transition metal electrodes as the moments are rotated from in-plane to out-of-plane in sufficiently large magnetic fields that the moments are nearly parallel to one another. A complex angular dependence of the tunneling resistance is found with twofold and fourfold components that vary strongly with bias voltage. Distinctly different TAMR behaviors are obtained for devices formed with highly textured crystalline MgO(001) and amorphous Al2O3 tunnel barriers. A tight-binding model shows that a fourfold angular dependence can be explained by the presence of an interface resonant state that affects the transmission of the contributing tunneling states through a spin-orbit interaction.