Micromagnetic investigation of current-driven magnetic excitation in a spin valve structure

Using micromagnetic modelling we study current-driven magnetic dynamics in a spin valve structure. We take into account the Slonczewski's spin torque term and the Oersted field due to charge current. Special attention is paid to excitation of the incoherent spin-wave induced by the spin torque which significantly affects the switching current, switching time and telegraph noise. The incoherence is mainly due to spatial inhomogeneity of local magnetic fields, which generate a distribution of local precession frequencies. Here we show the main consequences of the incoherent spin-wave which provides a quantitative understanding of the experimental results on magnetic dynamics due to spin-transfer effects. We also discuss the limitations and perspectives of micromagnetic modelling for the current-driven dynamics.