We have investigated spin pumping from ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ thin films into Cu, Ag, Ta, W, Pt, and Au with varying spin-orbit coupling strengths. From measurements of Gilbert damping enhancement and inverse spin Hall signals spanning 3 orders of magnitude, we determine the spin Hall angles and interfacial spin mixing conductances for the six metals. The spin Hall angles largely vary as $Z^4$ ($Z$: atomic number), corroborating the role of spin-orbit coupling. Amongst the four 5d metals, the variation of the spin Hall angle is dominated by the sensitivity of the $d$-orbital moment to the $d$-electron count, confirming theoretical predictions.

• Received 23 September 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.197201