Observation of unconventional spin polarization induced spin orbit torque in L1$_2$-ordered antiferromagnetic Mn$_3$Pt thin films

TL;DR

This study demonstrates unconventional spin orbit torque in L1$_2$-ordered Mn$_3$Pt thin films, revealing a unique orientation-dependent behavior linked to the topologically nontrivial spin structure, advancing understanding of charge-spin conversion in antiferromagnets.

Contribution

First observation of orientation-dependent unconventional spin orbit torque in L1$_2$-Mn$_3$Pt, connecting topological spin structures with charge-spin conversion mechanisms.

Findings

Unconventional spin orbit torque observed along the x-direction.

Sign reversal of torque relative to crystalline orientation.

Attribution of torque to magnetic spin Hall effect.

Abstract

Non-collinear antiferromagnets exhibits richer magneto-transport properties due to the topologically nontrivial spin structure they possess compared to conventional nonmagnetic materials, which allows us to manipulate the charge-spin conversion more freely by taking advantage of the chirality. In this work, we explore the unconventional spin orbit torque of L1$_2$-ordered Mn$_3$Pt with a triangular spin structure. We observed an unconventional spin orbit torque along the $\mathbf{x}$-direction for the (001)-oriented L1$_2$ Mn$_3$Pt, and found that it has a unique sign reversal behavior relative to the crystalline orientation. This generation of unconventional spin orbit torque for L1$_2$-ordered Mn$_3$Pt can be interpreted as stemming from the magnetic spin Hall effect. This report help clarify the correlation between the topologically nontrivial spin structure and charge-spin conversion in non-collinear antiferromagnets.