  The dependence of the spin pumping efficiency and the spin mixing conductance
on the surface processing of yttrium iron garnet (YIG) before the platinum (Pt)
deposition has been investigated quantitatively. The ferromagnetic resonance
driven spin pumping injects a spin polarized current into the Pt layer, which
is transformed into an electromotive force by the inverse spin Hall effect. Our
experiments show that the spin pumping effect indeed strongly depends on the
YIG/Pt interface condition. We measure an enhancement of the inverse spin Hall
voltage and the spin mixing conductance of more than two orders of magnitude
with improved sample preparation.
