Effect of the Angle-Dependent Gilbert Damping Constant on the Magnetization Dynamics Induced by a Spin Polarized Current

We performed macrospin simulations for a spin valve structure to investigate magnetization dynamics induced by spin torque. We took into account angle-dependent variation of the Gilbert damping constant and thermal fluctuation field which is caused by spin pumping. Switching probability of the current induced magnetization switching was little affected by the angle-dependence. It is because the critical current density depends on the Gilbert damping constant at the collinear magnetic configuration, either parallel or antiparallel. However, the precession frequency and the full-width at half-maximum at the frequency were significantly affected. We interpreted the effect of the angle-dependent Gilbert damping on the precession motion by means of an angle average of the enhanced damping constant