Current induced spin injection and surface torque in ferromagnetic metallic junctions

Joint influence of two effects, namely, nonequilibrium spin injection by current, and current induced surface torque, on spin-valve type ferromagnetic metallic junctions is considered theoretically. The CPP configuration is assumed. The consideration is based on solving a coupled set of equations of motion for the mobile electron and lattice magnetizations. Boundary conditions are derived from the total magnetization flux continuity condition. A dispersion relation is derived for current dependent spin-wave fluctuations. The fluctuations become unstable under current density exceeding some threshold value. Joint action of the longitudinal spin injection and the torque lowers the instability threshold. The spin injection softens spin wave frequency near the threshold and can pin magnetization at the injecting contact. The pinning rises under the current increasing, so that the appearance of new spin-wave resonance lines can be observed.