Moderate Positive Spin Hall Angle in Uranium*

We will present results on FMR and voltage measurements of magnetic damping and the inverse spin Hall effect, respectively, in Ni$_{80}$Fe$_{20}$/Uranium bilayers. A pure spin current is injected into an Uranium film from the ferromagnetic resonance dynamics of the magnetization of an adjacent Ni$_{80}$Fe$_{20}$ (permalloy) film. The spin current generated is then converted into an electric field by the inverse spin Hall effect. Our results suggest a spin mixing conductance of order 2x10$^{19}$ m$^{-2}$ and a positive spin Hall angle of 0.004, which are both unexpected based on trends in d-electron systems. These results support the idea that materials with unfilled f-electron orbitals may require additional exploration for spin physics.