Efficient spin transport across a disordered magnetic insulator/heavy metal interface

Devices based on spin wave excitations can provide an efficient alternative to conventional electronics with potential applications in memory, communications, and information systems. One approach relies on a low-loss magnetic insulator for the propagation of spin waves generated by the spin Hall effect of an adjacent heavy metal, where efficient spin transport at the heavy metal/insulating magnet interface is required. Although efficient spin transfer often coincides with a sharp materials interface, we provide evidence of efficient spin transport across a ~1 nm disordered interfacial layer that forms at the interface of low-loss lithium aluminum ferrite (LAFO) and tantalum. The presence of this interfacial layer is confirmed with transmission electron microscopy, and the spin transparency of the LAFO/Ta interface is studied through measurements of the spin Hall magnetoresistance, ferromagnetic resonance broadening, and the inverse spin Hall effect at room temperature. We extract an interfacial spin mixing conductance on the order of 10¹⁴ Ω^-1m^-2, on par with the most efficient interfaces, suggesting a poor interfacial quality is not necessarily preclusive of efficient spin transport.