Spin-Splitting Magnetoresistance in Altermagnetic RuO2 Thin Films

TL;DR

This study demonstrates a novel spin-splitting magnetoresistance effect in RuO2 thin films, revealing the Neel vector orientation and providing a new method to probe altermagnetic order in spintronics applications.

Contribution

It provides the first experimental evidence of altermagnetic spin-splitting magnetoresistance in RuO2, clarifying its magnetic order and introducing a new electric detection method.

Findings

Identification of a sizable SSMR in RuO2/Co bilayers

Unveiling the Neel vector along [001] in RuO2

Temperature dependence of the SSMR effect

Abstract

The recently discovered altermagnets, featured by the exotic correlation of magnetic exchange interaction and alternating crystal environments, have offered exciting cutting-edge opportunities for spintronics. Nevertheless, the altermagnetism of RuO2, one of the earliest-discovered altermagnets, is currently under intense debate. Here we try to resolve this controversy by demonstrating an altermagnetic spin-splitting magnetoresistance (SSMR) effect that is driven by a spin current associated with the giant nonrelativistic spin splitting of an altermagnet. Compared to the spin Hall magnetoresistance induced by a conventional relativistic spin current, the SSMR is characterized by unusual angular dependence with a phase-shift feature underpinned by the Neel-vector orientation and pronounced temperature dependence caused by its susceptibility to electron scattering. Through systematical investigations on the magnetoresistance of (101)-RuO2/Co bilayers, we disentangle a sizable SSMR and hence unveil a Neel vector along [001] direction. Our work not only demonstrates a simple electric avenue to probing the Neel vector of altermagnets, but also indicates long-range magnetic order in thin films of RuO2.