Spin pumping in YIG/Pt bilayers as a function of layer thickness

We systematically investigate the spin-pumping effect in a series of yttrium-iron-garnet (YIG)--platinum (Pt) bilayers, comparing both broadband ferromagnetic resonance and electrically detected spin-pumping experiments. We infer the effective spin-mixing conductance as a function of YIG and Pt layer thickness from ferromagnetic resonance measurements on pure YIG layers as well as on bilayer YIG/Pt samples in a frequency range from 2 to 20 GHz. In bare YIG films, we determine a Gilbert damping constant of approximately $\ensuremath{\alpha}=0.001$. With an additional platinum layer on top of the YIG samples, the damping is significantly enhanced. The effective spin-mixing conductance extracted from the ferromagnetic resonance experiments is in agreement with that determined from independent electrically detected spin-pumping experiments.