  From spin pumping measurements in Ta/Py devices for different thicknesses of
Ta, we determine the spin Hall angle to be 0.021 - 0.033 and spin diffusion
length to be 8 nm in Ta. We have also studied the effect of changing the
properties of non-magnet/ferromagnet interface by adding a Cu interlayer. The
experimental results show that the effective spin mixing conductance increases
in the presence of Cu interlayer for Ta/Cu/Py devices, whereas it decreases in
Pt/Cu/Py devices. Our findings allow the tunability of the spin pumping
efficiency by adding a thin interlayer at the non-magnet/ferromagnet interface.

Materials Science;Mesoscale and Nanoscale Physics