Magnetization self-oscillations induced by spin-polarized currents

Spin-polarized currents may exert significant torques on nanoscale ferromagnets. Experiments show that both switching and microwave oscillations of the magnetization are induced when the system is subject to the spin-polarized current and an external magnetic field. Under these conditions the nanomagnet behaves like a nonlinear system forced far from equilibrium by the current. For this reason, the correct framework for the study of the problem is nonlinear dynamical system theory and bifurcation theory. In this work, we present a method based on these ideas whereby an analytical description of the magnetization dynamics is worked out by taking advantage of the fact that both intrinsic damping and spin transfer effects can be treated as perturbations of the free precessional dynamics. The information obtained in this manner leads to predictions and explanations of many experimental results, recently reported in the literature.