Anisotropic spin dynamics in antiferromagnets with a nonrelativistic spin splitting

TL;DR

This paper investigates the highly anisotropic spin dynamics in antiferromagnets with nonrelativistic spin splitting, revealing how external magnetic fields can control spin relaxation, with implications for experimental identification and applications.

Contribution

It demonstrates that $d$-wave nonrelativistic spin splitting causes extreme anisotropic spin relaxation, and shows how magnetic fields can modulate this behavior, providing new insights into spin dynamics in antiferromagnets.

Findings

Spin dynamics are highly anisotropic due to $d$-wave NSS.

External magnetic fields can suppress or induce relaxation of spin components.

The results serve as experimental fingerprints for altermagnets.

Abstract

Antiferromagnets (AFM) with a nonrelativistic spin splitting (NSS) of electronic bands expand the range of spin-dependent phenomena and their applications. A crucial understanding for both of them pertains to the inherent spin dynamics. We demonstrate that the $d$-wave NSS gives rise to extremely anisotropic spin dynamics of carriers driven by the relaxation induced by motional narrowing. In contrast to the no relaxation of the spin polarization along the Neel vector, the dynamics of perpendicular spin components greatly varies from a long relaxation for a weak NSS to the fast-decaying oscillations for a strong NSS, a regime relevant to AFM with the $d$-wave NSS. The extreme anisotropy of the spin relaxation is transformed by the external magnetic field, which triggers the relaxation of the parallel spin component and also suppresses all the relaxation rates at larger magnitudes. The predicted spin dynamics of the $d$-wave NSS, known also from altermagnets, can be used as their experimental fingerprints and guide future applications.