Nonadiabatic stochastic resonance of a nanomagnet excited by spin torque.

We report microwave-frequency magnetization dynamics coexcited by alternating spin torque and thermal fluctuations. In these dynamics, temperature strongly enhances the amplitude of magnetization precession and enables excitation of nonlinear dynamic states of magnetization by weak alternating spin torque. We explain these thermally-activated dynamics in terms of nonadiabatic stochastic resonance of magnetization driven by spin torque.