Magnetization self-organization in a single-domain ferromagnet subject to a spin current

The Landau-Lifshitz equation for the magnetization dynamics of a single-domain magnetic system is solved using the methods of self-organization. The description takes into account the torque due to spin transfer. The potential energy of the system includes the uniaxial and easy-plane anisotropies, and the Zeeman energy due to an external magnetic field. The equilibrium and stationary states are investigated as a function of the spin current and external magnetic field. The presented bifurcation diagram allows to determine the margins of a neutral stability mode of the equilibrium and stationary states for different values of the easy-plane anisotropy constant. Using the power spectral density method, the trajectory tracing, Hausdorff dimension, and maximum Lyapunov exponent, the dynamics of the phase states in an external magnetic field is demonstrated. The analytical transcendent equations for switching between different equilibrium states are also obtained, proving the importance of phase averaging.