  We report measurements of spin pumping and the inverse spin Hall effect in
Ni80Fe20/Uranium bilayers designed to study the efficiency of spin-charge
interconversion in a super-heavy element. We employ broad-band ferromagnetic
resonance on extended films to inject a spin current from the Ni80Fe20
(permalloy) into the uranium layer, which is then converted into an electric
field by the inverse spin Hall effect. Surprisingly, our results suggest a spin
mixing conductance of order 2x10 e19 m-2 and a positive spin Hall angle of
0.004, which are both merely comparable to those of several transition metals.
These results thus support the idea that the electronic configuration may be at
least as important as the atomic number in governing spin pumping across
interfaces and subsequent spin Hall effects. In fact, given that both the
magnitude and the sign are unexpected based on trends in d-electron systems,
materials with unfilled f-electron orbitals may hold additional exploration
avenues for spin physics.
