Enhanced spin pumping damping in yttrium iron garnet/Pt bilayers

Detailed measurements of the magnetic relaxation expressed in the linewidth of the ferromagnetic resonance (FMR) absorption in thick films of yttrium iron garnet (YIG) and in YIG/Pt bilayers carried out at room temperature reveal a very large increase in the relaxation rate with the deposition of a Pt layer. The additional relaxation increases linearly with the microwave frequency characteristics of the spin pumping mechanism. The value of the spin mixing conductance obtained from the data is one order of magnitude larger than the largest possible value determined from measurements of the voltage generated by FMR spin-pumping. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773993]