Anisotropic tunneling magnetoresistance and tunneling anisotropic magnetoresistance: spin-orbit coupling in magnetic tunnel junctions

TL;DR

This paper investigates how spin-orbit coupling influences tunneling magnetoresistance effects in magnetic tunnel junctions, deriving analytical expressions and exploring anisotropic phenomena caused by interface interactions.

Contribution

It introduces a model linking spin-orbit interactions to TAMR and ATMR effects, providing analytical expressions and symmetry-based insights for ferromagnet/semiconductor/metal junctions.

Findings

Spin-orbit interaction induces TAMR and ATMR effects.

The anisotropic magnetoresistance depends on magnetization directions.

Model calculations for Fe/GaAs/Fe junctions support the theoretical predictions.

Abstract

The effects of the spin-orbit interaction on the tunneling magnetoresistance of ferromagnet/semiconductor/normal metal tunnel junctions are investigated. Analytical expressions for the tunneling anisotropic magnetoresistance (TAMR) are derived within an approximation in which the dependence of the magnetoresistance on the magnetization orientation in the ferromagnet originates from the interference between Bychkov-Rashba and Dresselhaus spin-orbit couplings that appear at junction interfaces and in the tunneling region. We also investigate the transport properties of ferromagnet/semiconductor/ferromagnet tunnel junctions and show that in such structures the spin-orbit interaction leads not only to the TAMR effect but also to the anisotropy of the conventional tunneling magnetoresistance (TMR). The resulting anisotropic tunneling magnetoresistance (ATMR) depends on the absolute magnetization directions in the ferromagnets. Within the proposed model, depending on the magnetization directions in the ferromagnets, the interplay of Bychkov-Rashba and Dresselhaus spin-orbit couplings produces differences between the rates of transmitted and reflected spins at the ferromagnet/seminconductor interfaces, which results in an anisotropic local density of states at the Fermi surface and in the TAMR and ATMR effects. Model calculations for Fe/GaAs/Fe tunnel junctions are presented. Furthermore, based on rather general symmetry considerations, we deduce the form of the magnetoresistance dependence on the absolute orientations of the magnetizations in the ferromagnets.