Vortex oscillations induced by spin-polarized current in a magnetic nanopillar: Analytical versus micromagnetic calculations

We investigate the vortex excitations induced by a spin-polarized current in a magnetic nanopillar by means of micromagnetic simulations and analytical calculations. Damped motion, stationary vortex rotation and the switching of the vortex core are successively observed for increasing values of the current. We demonstrate that even for small amplitude of the vortex motion, the analytical description based on the classical Thiele approach can yield quantitatively and qualitatively unsound results. We show that the energy dissipation function, which is calculated respecting rotational motion of the vortex, can be used for qualitative analytical description of the system.