Spin transport at a heavy metal/ferrimagnetic insulator interface above and below the Curie temperature

Spin wave spintronics are an attractive alternative to conventional electronics with potential for improved energy efficiency and processing speed. Practical implementation requires a low damping magnetic insulator allowing for coherent excitation and propagation of spin waves, typically generated using the spin Hall effect of an adjacent metal. One candidate is the recently developed thin film lithium aluminum ferrite (LAFO)[1]. In this work, we demonstrate spin transport at a Ta/LAFO interface probed via the spin Hall magnetoresistance (SHMR). Tantalum films 2-20 nm thick were sputtered onto 4 nm LAFO films; at this LAFO thickness, the Ta/LAFO Curie temperature is below 300 K, suppressed from that of single layer LAFO films. The SHMR contribution to the resistivity was determined by measuring the angle-dependent magnetoresistance (ADMR) in a saturating magnetic field. From the Ta thickness dependence of the SHMR we extract a spin diffusion length of ~1 nm and spin Hall angle of ~0.05 in Ta as well as a spin mixing conductance of ~10¹⁴ Ω ^-1 m^-2 at the Ta/LAFO interface. The ADMR is consistent above and below the Ta/LAFO Curie temperature and is similar to that of other systems associated with efficient spin transport.

[1] X.Y. Zheng et al., Nat. Commun. 14, 4918 (2023)