Tilted spin current generated by the collinear antiferromagnet RuO2

TL;DR

This paper demonstrates that canted Neel vectors in RuO2 generate a significant out-of-plane damping-like torque via a tilted spin current, revealing an antiferromagnetic spin Hall effect with unique symmetry properties.

Contribution

It provides experimental evidence of a tilted spin current in RuO2 caused by electric fields, highlighting a novel antiferromagnetic spin Hall effect with distinct symmetry features.

Findings

Out-of-plane damping-like torque observed in RuO2

Angular dependence matches predictions of a tilted spin current

Signature of a unique antiferromagnetic spin Hall effect

Abstract

We report measurements demonstrating that when the Neel vector of the collinear antiferromagnet RuO2 is appropriately canted relative to the sample plane, the antiferromagnet generates a substantial out of plane damping-like torque. The measurements are in good accord with predictions that when an electric field, E is applied to the spin split band structure of RuO2 it can cause a strong transverse spin current even in the absence of spin-orbit coupling. This produces characteristic changes in all three components of the E induced torque vector as a function of the angle of E relative to the crystal axes, corresponding to a spin current with a well defined tilted spin orientation s approximately (but not exactly) parallel to the Neel vector, flowing perpendicular to both E and S. This angular dependence is the signature of an antiferromagnetic spin Hall effect with symmetries that are distinct from other mechanisms of spin-current generation reported in antiferromagnetic or ferromagnetic materials.