Magnetic Vortex Dynamics Induced by an Electrical Current

Amagnetic nanoparticle in a vortex state is a promising candidate for the information storage. One bit of information corresponds to the upward or downward magnetization of the vortex core (vortex polarity). The dynamics of the magnetic vortex driven by a spin current is studied theoretically. Using a simple analytical model and numerical simulations, we show that a nondecaying vortex motion can be excited by a dc spin–polarized current, whose intensity exceeds a first threshold value as a result of the balance between a spin-torque pumping and damping forces. The irreversible switching of the vortex polarity takes place for a current above a second threshold. The mechanism of the switching, which involves the process of creation and annihilation of a vortex–antivortex pair is described analytically, using a rigid model, and confirmed by detailed spin–lattice simulations. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem 110: 83–97, 2010