We examine a spin torque induced by the Rashba spin-orbit coupling in three dimensions within the Boltzmann transport theory. We analytically calculate the spin torque and show how its behavior is related with the spin topology in the Fermi surfaces by studying the Fermi-energy dependence of the spin torque. Moreover we discuss the spin-torque efficiency which is the spin torque divided by the applied electric current in association with the current-induced magnetization reversal. It is found that high spin-torque efficiency is achieved when the Fermi energy lies on only the lower band and there exists an optimal value for the Rashba parameter, where the spin-torque efficiency becomes maximum.

The electron mobility of In-Ga-Zn-oxide (IGZO) is known to be enhanced by higher In content. We theoretically investigated the mobility-enhancement mechanism by proposing an In-Ga-Zn-disorder scattering model for an In-rich crystalline IGZO (In1+xGa1−xO3(ZnO)m (0 < x < 1, m > 0)) thin film. The obtained theoretical mobility was found to be in agreement with experimental Hall mobility for a crystalline In1.5Ga0.5O3(ZnO) (or In3GaZn2O8) thin film. The mechanism specific to In-rich crystalline IGZO thin films is based on three types of Coulomb scattering potentials that originate from effective valence differences. In this study, the In-Ga-Zn-disorder scattering model indicates that the effective valence of the In3+ ions in In-rich crystalline IGZO thin films significantly affects their electron mobility.

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We investigate the spin-current absorption induced by an inhomogeneous spin-orbit coupling due to impurities in metals. We consider the system with spin currents driven by the electric field or the spin accumulation. The resulting diffusive spin currents, including the gradient of the spin-orbit coupling strength, indicate the spin-current absorption at the interface, which is exemplified with experimentally relevant setups.