Control of spins in a nano-sized magnet using electric-current

With the development of spintronics, spin-transfer torque control of magnetic properties receives considerable attention. In this paper the Landau-Lifshitz-Gilbert equation including the torque term is used to investigate the magnetic moment dynamics in the free layer of the ferromagnet/non-magnetic/ferromagnet (FM1/N/FM2) structures. It is found that the reverse critical time τ_c decreases with the current increasing. The critical time τ_c as a function of current for the perpendicular and parallel easy magnetic axes are the same. The critical time τ_c increases with the damping factor α increasing. In the case of large current the influence of the damping factor α is smaller, but in the case of little torque the critical time τ_c increases greatly with the damping increasing. The direction of the magnetization in the fixed layer influences the critical time, when the angle between the magnetization and the z direction changes from 0.1π to 0.4π, the critical time τ_c decreases from 26.7 to 15.6.