Large Tunneling Anisotropic Magnetoresistance mediated by Surface States

TL;DR

This study explores the tunneling anisotropic magnetoresistance (TAMR) in cobalt films, revealing a significant 30% effect at cryogenic temperatures caused by surface states influenced by spin-orbit interactions.

Contribution

It demonstrates the first detailed link between surface states, spin-orbit coupling, and TAMR in thick cobalt films using combined experimental and theoretical approaches.

Findings

TAMR reaches up to 30% at -350 mV

Sign reversal of TAMR with voltage dependence

Surface states exhibit spin-orbit induced hybridization

Abstract

We investigated the tunneling anisotropic magnetoresistance (TAMR) in thick hcp Co films at cryogenic temperatures using scanning tunneling microscopy. At around -350 mV, a strong TAMR up to 30\% is found with a characteristic voltage dependence and a reversal of sign. With the help of \textit{ab initio} calculations the TAMR can be traced back to a spin-polarized occupied surface states that experience a strong spin-orbit interaction leading to a magnetization direction depending hybridization with bulk states.