Absence of detectable MOKE signals from spin Hall effect in metals

摘要

Recently, observation of the magneto-optical Kerr effect (MOKE) from the spin Hall effect (SHE) in beta-tungsten (β-W) and platinum (Pt) films was reported in the literature. This is most interesting, as it would provide an alternative means to probe the SHE in metals. However, despite repeated attempts on different samples, we were unable to find a true SHE-induced MOKE signal from β-W and Pt even with a current density of 2.5 × 10~5A/cm~2. The results indicate that the MOKE signal from the SHE in metals ought to be very weak, below the detection limit of currently available MOKE setups (0.08 mdeg). Our theoretical calculation shows that in order to observe an SHE-induced MOKE signal of 0.1 mdeg in β-W, one would need a driving current density of ～10~8A/cm~2.