Nonlinear Magnetization Dynamics in Nanomagnets Driven by Spin-Polarized Currents

Phenomenological description of spin-torque in nanomagnets: Landau-Lifshitz-Gilbert equation with Slonczewski spintorque term. Energy balance in magnetic systems driven by spin-polarized currents and nonconservative nature of dynamics. Determination of equilibria and self-oscillations (limit cycles). Perturbation approach: spin-torque driven dynamics as a perturbation of conservative (precessional) dynamics. Melnikov technique to study existence, stability and bifurcations of self-oscillatory regimes (limit cycles). Analysis of thermal stability in spin-torque driven magnetization dynamics. Fokker-Planck equation, averaging technique, and description based on the free energy probability distribution. Thermal relaxation and stationary (non-Boltzmann) energy distribution in spintorque systems. Defintion of effective potential barrier separating self-oscillatory regimes and equilibria. Arrhenius formula for spin-driven dynamics regimes.