Spatial symmetry of spin pumping and inverse spin Hall effect in the Pt/Y3Fe5O12 system

The spatial symmetry of spin pumping, i.e., the voltage amplitude of the inverse spin Hall effect varying with the orientation of static magnetization and the polarization direction of a dynamic magnetic field, has been systematically studied both theoretically and experimentally. This symmetry is quite important because it is the unique foundation and criterion for identifying the spin pumping signal from other contributions to the voltage and for unveiling the underlying physics of spin pumping and pure spin current. As a straightforward proof, we found the spin mixing conductance to be out-of-plane anisotropic, which comes from an elaborate study of the symmetry of a Pt/YIG bilayer after examining every effect that may contribute to the angular dependence of spin pumping; the spin Hall angle, however, is a constant that is independent of the polarization direction of the spin current.