Large spin Hall effect in an amorphous binary alloy

摘要

We investigate the spin Hall effect of W-Hf thin films, which exhibit a phase transition from a segregated phase mixture to an amorphous alloy below 70% W. The spin Hall angle was determined with a planar harmonic Hall voltage technique. Due to the accompanying jump in resistivity, the spin Hall angle shows a pronounced maximum at the composition of the phase transition. The spin Hall conductivity does, however, reduce from W to Hf with a weak discontinuity across the phase transition. The maximum spin Hall angle of θ_(SH) = -0.20 is obtained for amorphous W_(0.78)Hf_(0.3). A detailed comparison with spin Hall conductivities calculated from lirst principles for hcp, fcc, and bcc solid solutions provides valuable insight into the alloying physics of this binary system.