Influence of disorder at Insulator-Metal interface on spin transport

Motivated by experimental work showing enhancement of spin transport between Yttrium Iron Garnet and Platinum by a thin antiferromagnetic insulator between them, we consider spin transport through the interface of a non-magnetic metal and compensated antiferromagnetically ordered insulator and focus on the significance of the interface itself. The spin transport is carried by spin-polarized electrons in the metal and by magnons in the insulator. We compute the spin current in the presence of a spin accumulation in the metal, cause by the spin Hall effect, and a thermal gradient using Fermi's Golden Rule in the presence of interfacial disorder. For a perfectly clean interface, the in-plane momentum is conserved by the electron-magnon scattering events that govern the spin transport through the interface. We calculate how disorder-induced broadening of scattering matrix elements with respect to the in-plane momentum influences the spin current. As a general result, we observe that for many experimental setups, specifically for high temperatures, one should expect a rather small effect of interface disorder on the measured spin current, while for small temperatures there is a significant reduction of a spin current with increasing disorder.