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

Abstract

Although electron motion is prohibited in magnetic insulators, the electron spin can be transported by magnons. Such magnons, generated and detected using all-electrical methods, are now shown to travel micrometre distances at room temperature. The transport of spin information has been studied in various materials, such as metals1, semiconductors2 and graphene3. In these materials, spin is transported by the diffusion of conduction electrons4. 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 electrically5,6,7 in a linear response, and can transport spin angular momentum through the magnetic insulator yttrium iron garnet (YIG) over distances as large as 40 μm. We identify two transport regimes: the diffusion-limited regime for distances shorter than the magnon spin diffusion 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 spin diffusion length λ = 9.4 ± 0.6 μm in a thin 200 nm YIG film at room temperature.