  Using the Boltzmann formalism based on the first principles electronic
structure and scattering rates, we investigate the current-induced spin
accumulation and spin-orbit torques in FePt/Pt and Co/Cu bilayers in the
presence of substitutional impurities. In FePt/Pt bilayers we consider the
effect of intermixing of Fe and Pt atoms in the FePt layer, and find a crucial
dependence of spin accumulation and spin-orbit torques on the details of the
distribution of these defects. In Co/Cu bilayers we predict that the magnitude
and sign of the spin-orbit torque and spin accumulation depend very sensitively
on the type of the impurities used to dope the Cu substrate. Moreover,
simultaneously with impurity-driven scattering we consider the effect of an
additional constant quasiparticle broadening of the states at the Fermi surface
to simulate phonon scattering at room temperature, and discover that even a
small broadening of the order of 25 meV can drastically influence the magnitude
of the considered effects. We explain our findings based on the analysis of the
complex interplay of several competing Fermi surface contributions to the spin
accumulation and spin-orbit torques in these structurally and chemically
non-uniform systems.
