Asymmetric Scattering-Induced Neel Spin-Orbit Torque in Antiferromagnets

TL;DR

This paper reveals that asymmetric impurity scattering, combined with band geometry, can generate a significant PT-odd spin polarization in antiferromagnets, offering a new mechanism for controlling Neel spin-orbit torque.

Contribution

It introduces a novel extrinsic mechanism involving asymmetric impurity scattering and band geometry that enhances Neel spin-orbit torque in antiferromagnets.

Findings

Asymmetric impurity scattering can produce PT-odd spin polarization.

The anomalous skew-scattering contribution can surpass conventional symmetric scattering.

This mechanism enables more efficient electrical control of antiferromagnetic states.

Abstract

Magnetic switching in antiferromagnets relies on Neel spin orbit torque (NSOT), which originates from a current-induced staggered spin polarization of itinerant electrons. In collinear antiferromagnets, such a response requires the spin susceptibility to be odd under combined space-time inversion symmetry (PT), and is conventionally attributed to symmetric scattering processes. Here, we demonstrate that asymmetric impurity scattering generates an additional PT-odd spin polarization when coupled with the anomalous spin polarizability (ASP) of Bloch electrons. This extrinsic contribution arises from the interplay between antisymmetric higher-order scattering processes and band geometry, effectively converting an otherwise PT-even susceptibility into a staggered spin polarization. Using a minimal model of tetragonal CuMnAs, we show that this anomalous skew-scattering contribution can be comparable to, and with sufficient impurity density even exceed, the conventional symmetric scattering (Drude) contribution. Our results identify a new band-geometry-driven mechanism for NSOT and establish an efficient route for electrical control of antiferromagnets.