Observation of nonreciprocal magnon Hanle effect

TL;DR

This paper reports the observation of a nonreciprocal magnon Hanle effect in hematite, demonstrating controllable nonreciprocity in magnon spin transport, which could enable new antiferromagnetic spintronic devices.

Contribution

It introduces the first observation of nonreciprocal magnon Hanle effect in hematite, revealing a controllable pseudofield-dependent nonreciprocity in antiferromagnetic spin transport.

Findings

Nonreciprocal magnon Hanle signals observed in hematite.

Interchanging injector/detector alters the magnon signal.

Nonreciprocity depends on magnetic field and reverses at the compensation field.

Abstract

The precession of magnon pseudospin about the equilibrium pseudofield, the latter capturing the nature of magnonic eigen-excitations in an antiferromagnet, gives rise to the magnon Hanle effect. Its realization via electrically injected and detected spin transport in an antiferromagnetic insulator demonstrates its high potential for devices and as a convenient probe for magnon eigenmodes and the underlying spin interactions in the antiferromagnet. Here, we observe a nonreciprocity in the Hanle signal measured in hematite using two spatially separated platinum electrodes as spin injector/detector. Interchanging their roles was found to alter the detected magnon spin signal. The recorded difference depends on the applied magnetic field and reverses sign when the signal passes its nominal maximum at the so-called compensation field. We explain these observations in terms of a spin transport direction-dependent pseudofield. The latter leads to a nonreciprocity, which is found to be controllable via the applied magnetic field. The observed nonreciprocal response in the readily available hematite films opens interesting opportunities for realizing exotic physics predicted so far only for antiferromagnets with special crystal structures.