Long distance transport of magnon spin information in a magnetic insulator at room temperature

TL;DR

This study demonstrates that non-equilibrium magnons in a magnetic insulator can be electrically excited, detected, and can transport spin information over large distances at room temperature, revealing two distinct transport regimes.

Contribution

It provides the first experimental evidence of fully electrical excitation and detection of magnons transporting spin in a magnetic insulator at room temperature.

Findings

Magnons can be transported over 40 micrometers in YIG.

Identified diffusion and relaxation regimes in magnon transport.

Extracted magnon relaxation length of 9.4 micrometers.

Abstract

The transport of spin information has been studied in various materials, such as metals, semiconductors and graphene. In these materials, spin is transported by diffusion of conduction electrons. Here we study the diffusion and relaxation of spin in a magnetic insulator, where the large bandgap prohibits the motion of electrons. Spin can still be transported, however, through the diffusion of non-equilibrium magnons, the quanta of spin wave excitations in magnetically ordered materials. Here we show experimentally that these magnons can be excited and detected fully electrically in linear response, and can transport spin angular momentum through the magnetic insulator yttrium iron garnet (YIG) over distances as large as 40 micrometer. We identify two transport regimes: the diffusion limited regime for distances shorter than the magnon relaxation length, and the relaxation limited regime for larger distances. With a model similar to the diffusion-relaxation model for electron spin transport in (semi)conducting materials, we extract the magnon relaxation length lambda = 9.4 micrometer in a 200 nm thin YIG film at room temperature.