Spin-Transfer-Driven Magnetization Dynamics

Analytical methods are discussed for the study of spin-transfer-driven magnetization dynamics in nanomagnets. Particular emphasis is given to the case of uniformly magnetized systems, which is a key prerequisite before attempting any numerical computation of complex spin-transfer devices. The onset of current-induced microwave oscillations of the magnetization is analyzed in the frame of nonlinear dynamical system theory and bifurcation theory. Methods for the description of the effect of thermal fluctuations by appropriate Langevin or Fokker-Planck equations are also considered. It is shown that for systems exhibiting uniaxial symmetry the analytical treatment can be developed in considerable detail without introducing any approximation.