  We have measured the spin torques of beta-Tantalum / Co20Fe60B20 bilayers
versus Ta thickness at room temperature using an FMR technique. The spin Hall
coefficient was calculated both from the observed change in damping coefficient
of the ferromagnet with Ta thickness, and from the ratio of the symmetric and
anti-symmetric components of the FMR signal. Results from these two methods
yielded values for the spin Hall coefficient of -0.090+/-0.005 and
-0.11+/-0.01, respectively. We have also identified a significant out-of-plane
spin torque originating from Ta, which is constant with Ta thickness. We
ascribe this to an interface spin orbit coupling, or Rashba effect, due to the
strength and constancy of the torque with Ta thickness. From fitting measured
data to a model including interface spin orbit coupling, we have determined the
spin diffusion length for beta-Tantalum to be ~2.5 nm.
