Nonlinear magnetization dynamics and magnetization switching in uniformly magnetized bodies

Magnetization dynamics in uniformly magnetized ferromagnetic bodies is studied by using Landau-Lifshitz-Gilbert (LLG) equation. This equation is written in a generalized form to take into account the effect of spin-polarized currents. The general properties of the corresponding nonlinear dynamical system are studied in detail. It is underlined that, in many experimental situations relevant to magnetic storage applications, LLG dynamics is a small perturbation of conservative precessional dynamics. In this respect, the conservative case is treated in detail and it is shown that analytical solutions of the conservative dynamics can be derived by using the existence of two integrals of motion. The (perturbed) dissipative LLG dynamics is then studied by developing appropriate perturbation techniques. The general methods of analysis discussed in the first part of the paper are applied to two particular problems: precessional switching and current-driven switching. The accuracy of theoretical predictions are tested by comparing analytical results with numerical solutions.