X-ray imaging of nonlinear resonant gyrotropic magnetic vortex core motion in circular permalloy disks

Abstract

We report experimental evidence of nonlinear gyrotropic vortex core motion. Using soft x-ray transmission microscopy we observed the time-averaged dynamic response of a magnetic vortex core in a 2 μm diameter, 100 nm thick permalloy (Ni 80Fe 20) disk as a function of the amplitude and frequency of an applied RF magnetic field. At lower amplitude fields a single resonance was observed, but two distinct resonances, above and below the low amplitude resonance frequency, were observed when higher amplitude fields were applied. The results are discussed in the context of a nonlinear vortex energy potential. © 2012 American Institute of Physics.