Long-distance spin transport in a disordered magnetic insulator

Spin transport through magnetic insulators via magnons has been explored for a variety of crystalline materials. Here we show dramatic effects of spin transport through an amorphous magnetic insulator, which is both magnetically and structurally disordered. We observe spin flow though amorphous yttrium-iron-garnet (a-YIG) thin films in a non-local geometry by use of the spin Hall and inverse spin Hall effects in platinum strips separated by ten or more micrometres. By comparing a-YIG grown on suspended micromachined thermal isolation platforms to the same film on bulk substrates, we show strong effects of in-plane thermal gradients on spin transport in the disordered film. The resulting signals are orders of magnitude larger than those seen in crystalline magnetic insulators, and easily measurable even for distances greater than 100 mu m. In analogy to heat transport in glasses, where a range of vibrational excitations can allow large thermal conductivities, we suggest that effcient spin transport in disordered systems can occur via a similar spectrum of excitations that relies on strong local exchange interactions and does not require long-range order. This opens a new area for experimental and theoretical studies of spin transport, and sets a new direction in materials science for magnonic and spintronic devices.