Spin transport in disordered materials via antiferromagnetic correlations

Spin transport through ferromagnetic and antiferromagnetic (AF) insulators is an exciting new direction in spintronics. We have added a dramatic twist to this evolving picture by demonstrating long-distance spin transport in disordered magnetic insulators.[1] This work follows on recent electrical generation and detection of spin transport through the crystalline ferrimagnetic insulator yttrium iron garnet (YIG). These non-local transport experiments excite spin dynamics in the YIG via the spin Hall effect (SHE), and detect a spin current some distance away using the inverse spin Hall effect (ISHE). We have carried out similar experiments on amorphous YIG (a-YIG), a material with no long- or medium-range order (either structural or magnetic), and shown surprisingly long length-scale spin transport with measurable signals even for distances greater than 100 microns. Experiments on a-YIG supported both on a bulk substrate and on suspended Si-N membrane thermal platforms show that spin injection and transport does not require thermal gradients, but that the presence of in-plane thermal gradients enhances spin transport and reveals a large non-equilibrium spin thermal conductance. Among other intriguing aspects of this unexpected spin transport, we clarify that the effects are large not in a previously known low-temperature spin-glass state, but only at higher temperatures where only AF spin correlations are present. We will present recent further evidence of an origin of these results in spin transport, show similar effects in a second disordered magnetic material, and argue that the role of AF correlations is a more general feature that is seen even in spin transport through more structurally ordered systems.

[1] D. Wesenberg, T. Liu, D. Balzar, M. Wu and B. L. Zink, Nature Physics 13, 987–993 (2017)