YIG thickness and frequency dependence of the spin-charge current conversion in YIG/Pt systems

We report the frequency dependence of the spin current emission in a hybrid ferrimagnetic insulator/normal metal system as function of the insulating layer thickness. The system is based on a yttrium iron garnet (YIG) film [0.2, 1, and 3 \mu m] grown by liquid-phase-epitaxy coupled with a spin current detector of platinum [6 nm]. A strong YIG thickness dependence of the efficiency of the spin pumping has been observed. The highest conversion factor \Delta V/P_{abs} has been demonstrated for the thinner YIG (1.79 and 0.55 mV/mW^{-1} at 2.5 and 10 GHz, respectively) which presents an interest for the realisation of YIG-based devices. A strong YIG thickness dependence of the efficiency of the spin pumping has been also observed and we demonstrate the threshold frequency dependence of the three-magnon splitting process.