Power spectrum of current-induced magnetization dynamics in uniaxial nanomagnets

Nanomagnets with uniaxial symmetry driven by spin polarized currents are considered, in which anisotropy, applied field, and spin polarization are all aligned along the symmetry axis. Thermal fluctuations are taken into account by adding a Gaussian white noise stochastic term to the equation for the deterministic dynamics. The corresponding Fokker-Planck equation is derived and it is solved by using separation of variable and eigenfunction expansion techniques. From the solution of the Fokker-Planck equation, the autocorrelation function and the power spectral density of magnetization are computed. The position and the linewidth of the peaks in the power spectral density are discussed in detail.