Spin torque dynamics with noise in magnetic nanosystems

We investigate the role of equilibrium and nonequilibrium noise in the magnetization dynamics on monodomain ferromagnets. Starting from a microscopic model, we present a detailed derivation of the spin shot-noise correlator. We investigate the ramifications of the nonequilibrium noise on the spin torque dynamics, both in the steady-state precessional regime and the spin switching regime. In the latter case, we apply a generalized Fokker-Planck approach to spin switching, which models the switching by an Arrhenius law with an effective elevated temperature. We calculate the renormalization of the effective temperature due to spin shot noise and show that the nonequilibrium noise leads to the creation of cold and hot spot with respect to the noise intensity.