Analytical Treatment of Nonlinear Ferromagnetic Resonance in Nanomagnets

We study magnetization oscillations in a uniformly magnetized nanomagnet driven by ac excitations (external fields and injected currents) when the frequency of excitation is close to ferromagnetic resonance frequency. By using separation of time scale and the averaging technique, we derive dynamical equations, which can be studied by the methods of dynamical systems theory. This leads to an analytical description of nonlinear frequency response and to the analysis of relevant bifurcation phenomena. The theoretical results are compared with numerical simulations.