Magnetization reversal in a ferromagnetic circular dot under current induced resonant excitation

A magnetic vortex core in a ferromagnetic circular dot can be resonantly excited by a spin- polarized AC current at the eigenfrequency determined by the con. ning potential. We studied the magnetic properties of the dot in its dynamical state with a vortex core on resonance as well as off resonance. Magnetoresistance measurements under the AC current revealed that the annihilation field of the vortex core is reduced in the resonance state compared to the off- resonance state. This may be due to the additional energy accompanying the resonant motion. (c) 2006 Elsevier B. V. All rights reserved.