Detection of Microwave Spin Pumping Using the Inverse Spin Hall Effect

Abstract : We report on the electrical detection of the dynamical part of the spin pumping current emitted during ferromagnetic resonance (FMR) using the inverse Spin Hall Effect (ISHE). The experiment is performed on a YIG|Pt bilayer. The choice of YIG, a magnetic insulator, ensures that no charge current flows between the two layers and only the pure spin current produced by the magnetization dynamics is transferred into the adjacent strong spin-orbit Pt layer via spin pumping. To avoid measuring the parasitic eddy currents induced at the frequency of the microwave source, a resonance at half the frequency is induced using parametric excitation in the parallel geometry. Triggering this nonlinear effect allows to directly detect on a spectrum analyzer the microwave component of the ISHE voltage. Signals as large as 30 µV are measured for precession angles of a couple of degrees. This direct detection provides a novel efficient means to study magnetization dynamics on a very wide frequency range with great sensitivity.