  We generalize magnetoelectronic circuit theory to account for spin transfer
to and from the atomic lattice via interfacial spin-orbit coupling. This
enables a proper treatment of spin transport at interfaces between a
ferromagnet and a heavy-metal non-magnet. This generalized approach describes
spin transport in terms of drops in spin and charge accumulations across the
interface (as in the standard approach), but additionally includes the
responses from in-plane electric fields and offsets in spin accumulations. A
key finding is that in-plane electric fields give rise to spin accumulations
and spin currents that can be polarized in any direction, generalizing the
Rashba-Edelstein and spin Hall effects. The spin accumulations exert torques on
the magnetization at the interface when they are misaligned from the
magnetization. The additional out-of-plane spin currents exert torques via the
spin-transfer mechanism on the ferromagnetic layer. To account for these
phenomena we also describe spin torques within the generalized circuit theory.
The additional effects included in this generalized circuit theory suggest
modifications in the interpretations of experiments involving spin orbit
torques, spin pumping, spin memory loss, the Rashba-Edelstein effect, and the
spin Hall magnetoresistance.
