An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit

TL;DR

This study demonstrates room temperature long-distance magnon spin transport in doped hematite antiferromagnetic thin films, revealing complex magnetic structures and tunable spin transport properties without significant damping increase.

Contribution

It introduces a doped hematite thin film with low magnetic symmetry capable of efficient spin transport at room temperature, with detailed analysis of magnon diffusion and field-dependent behavior.

Findings

Magnon spin-diffusion length up to 1.5 μm

Decay length of 175 nm for low frequency magnons

Doping does not significantly increase magnetic damping

Abstract

We report room temperature long-distance spin transport of magnons in antiferromagnetic thin film hematite doped with Zn. The additional dopants significantly alter the magnetic anisotropies, resulting in a complex equilibrium spin structure that is capable of efficiently transporting spin angular momentum at room temperature without the need for a well-defined, pure easy-axis or easy-plane anisotropy. We find intrinsic magnon spin-diffusion lengths of up to 1.5 {\mu}m, and magnetic domain governed decay lengths of 175 nm for the low frequency magnons, through electrical transport measurements demonstrating that the introduction of non-magnetic dopants does not strongly reduce the transport length scale showing that the magnetic damping of hematite is not significantly increased. We observe a complex field dependence of the non-local signal independent of the magnetic state visible in the local magnetoresistance and direct magnetic imaging of the antiferromagnetic domain structure. We explain our results in terms of a varying and applied-field-dependent ellipticity of the magnon modes reaching the detector electrode allowing us to tune the spin transport.