Interfacial spin-orbitronic effects controlled with different oxidation levels at the Co|Al interface

TL;DR

This study reveals how varying oxidation levels at the Co|Al interface significantly influence magnetic anisotropy and chiral interactions, challenging previous assumptions and highlighting the role of orbital hybridization and strain.

Contribution

It demonstrates the control of interfacial spin-orbitronic effects through oxidation and Al thickness, providing new insights into interface engineering in spintronics.

Findings

Double sign change in magnetic anisotropy with oxidation levels

Threefold variation in interfacial chiral interaction

Reversal of anisotropy at fully metallic Co|Al interface

Abstract

Perpendicular magnetic anisotropy (PMA) and Dzyaloshinskii-Moriya interactions are key interactions in modern spintronics. These interactions are thought to be dominated by the oxidation of the Co|Al interface in the archetypal Platinum-Cobalt-Aluminum oxide system. Here, we observe a double sign change in the anisotropy and about threefold variation in interfacial chiral interaction, influenced not only by the oxidation, but also by the metallic Al thickness. Contrary to previous assumptions about negligible spin-orbit effects at light metal interfaces, we not only observe strong PMA with fully oxidized Al, decreasing and turning negative (in-plane) with less oxygen at the Co|Al interface, we also observe that the magnetic anisotropy reverts to positive (out-of-plane) values at fully metallic Co|Al interface. These findings suggest modification in Co d band via Co|Al orbital hybridization, an effect supported by X-ray absorption spectroscopy and ab initio theory calculations, highlighting the key impact of strain on interfacial mechanisms at fully metallic Co|Al interface.