Controllable vortex polarity switching by spin polarized current

Magnetic dynamics of vortex core (VC) driven by spin polarized current are examined for a sandwiched nanopillar consisting of a fixed layer with perpendicular magnetization and a free layer in vortex state. The core switching is shown to be size dependent and it has suggested two distinct routes mediated either by vortex-antivortex creation and annihilation process or by a series of transient states of C and monodomain states.