Thickness and power dependence of the spin-pumping effect in Y3Fe5O12/Pt heterostructures measured by the inverse spin Hall effect

摘要

The dependence of the spin-pumping effect on the yttrium iron garnet(Y3Fe5O12, YIG) thickness detected by the inverse spin Hall effect (ISHE) hasbeen investigated quantitatively. Due to the spin-pumping effect driven by themagnetization precession in the ferrimagnetic insulator YIG film aspin-polarized electron current is injected into the Pt layer. This spincurrent is transformed into electrical charge current by means of the ISHE. Anincrease of the ISHE-voltage with increasing film thickness is observed andcompared to the theoretically expected behavior. The effective dampingparameter of the YIG/Pt samples is found to be enhanced with decreasing YIGfilm thickness. The investigated samples exhibit a spin mixing conductance ofg=(7.43 \pm 0.36) \times 10^{18} m^{-2} and a spin Hall angle of theta_{ISHE} =0.009 \pm 0.0008. Furthermore, the influence of nonlinear effects on thegenerated voltage and on the Gilbert damping parameter at high excitationpowers are revealed. It is shown that for small YIG film thicknesses abroadening of the linewidth due to nonlinear effects at high excitation powersis suppressed because of a lack of nonlinear multi-magnon scattering channels.We have found that the variation of the spin-pumping efficiency for thick YIGsamples exhibiting pronounced nonlinear effects is much smaller than thenonlinear enhancement of the damping.