Temperature dependence of the effective spin-mixing conductance probed with lateral non-local spin valves

We report the temperature dependence of the effective spin-mixing conductance between a normal metal (aluminium, Al) and a magnetic insulator (Y3Fe5O12, YIG). Non-local spin valves with Al spin transport channel were fabricated on top of YIG and SiO2 substrates. From the spin relaxation lengths in the Al channel
on the two different substrates, we extract the effective spin-mixing conductance (Gs) to be 3.3x10 12 Ω-1 m-2 at 293 K for the Al/YIG interface. A decrease of up to 84% in Gs is observed when the temperature (T) is decreased from 293 K to 4.2 K, with Gs scaling with T3=2. The real part of the spin-mixing conductance (Gr ≈5:7 x 1013 Ω1m-2), calculated from the experimentally obtained Gs, is found to be approximately independent of the temperature. We evidence a hitherto unrecognized underestimation of Gr extracted from the modulation of the spin signal by rotating the magnetization direction of YIG with respect to the spin accumulation direction in the Al channel, which is found to be 50 times smaller than the calculated value.