Torque induced by spin-polarized current in ferromagnetic single-electron transistors

We present theoretical analysis of the current-induced torque exerted on the magnetic moment of the central electrode (island) in a ferromagnetic single electron transistor with non-collinear magnetic moments of the electrodes. The considerations are restricted to the sequential tunneling regime, and the charge and spin currents are calculated within the master equation approach. The torque is calculated from the net spin current absorbed by the island. The calculations are carried out in the limit of fast spin relaxation processes, when no nonequilibrium magnetic moment can build up on the island.