  The spin Hall angle (SHA) is a measure of the efficiency with which a
transverse spin current is generated from a charge current by the spin-orbit
coupling and disorder in the spin Hall effect (SHE). In a study of the SHE for
a Pt$|$Py (Py=Ni$_{80}$Fe$_{20}$) bilayer using a first-principles scattering
approach, we find a SHA that increases monotonically with temperature and is
proportional to the resistivity for bulk Pt. By decomposing the room
temperature SHE and inverse SHE currents into bulk and interface terms, we
discover a giant interface SHA that dominates the total inverse SHE current
with potentially major consequences for applications.
