Micromagnetic study of spin transport in easy-plane antiferromagnetic insulators

TL;DR

This study uses micromagnetic simulations to demonstrate how external magnetic fields can control spin transport in easy-plane antiferromagnetic insulators through coherent magnon mode beating.

Contribution

It reveals a mechanism for finite spin transport in easy-plane antiferromagnets via coherent beating of orthogonal magnon modes, enabling on-demand control of spin signals.

Findings

Magnetic field tuning controls magnon eigenmodes and spin polarization.

Coherent beating between magnon modes explains finite spin transport.

Sign of spin signal is determined by mode interference.

Abstract

Magnon eigenmodes in easy-plane antiferromagnetic insulators are linearly polarized and are not expected to carry any net spin angular momentum. Motivated by recent nonlocal spin transport experiments in the easy-plane phase of hematite, we perform a series of micromagnetic simulations in a nonlocal geometry at finite temperatures. We show that by tuning an external magnetic field, we can control the magnon eigenmodes and the polarization of the spin transport signal in these systems. We argue that a coherent beating oscillation between two orthogonal linearly polarized magnon eigenmodes is the mechanism responsible for finite spin transport in easy-plane antiferromagnetic insulators. The sign of the detected spin signal is also naturally explained by the proposed coherent beating mechanism. Our finding opens a path for on-demand control of the spin signal in a large class of easy-plane antiferromagnetic insulators.