Torque due to spin-polarized current in ferromagnetic single-electron transistors

A theoretical analysis of current-induced torque acting on the magnetic moment of the central part (island) of a ferromagnetic single-electron transistor has been carried out in the regime of sequential tunnelling. The island is assumed to be ferromagnetic and attached to two leads (electrodes). One of the leads is ferromagnetic, and the corresponding magnetic moment is oriented arbitrarily. The torque is calculated from the spin current absorbed by the magnetic moment of the island, and calculations are carried out in the limit of fast spin relaxation on the island (no spin accumulation).