We observe the dynamics of a single magnetic vortex in the presence of a random array of pinning sites. At low excitation amplitudes, the vortex core gyrates about its equilibrium position with a frequency that is characteristic of a single pinning site. At high amplitudes, the frequency of gyration is determined by the magnetostatic energy of the entire vortex, which is confined in a micron-scale disk. We observe a sharp transition between these two amplitude regimes that is due to depinning of the vortex core from a local defect. The distribution of pinning sites is determined by mapping fluctuations in the frequency as the vortex core is displaced by a static in-plane magnetic field.
@article{arxiv.cond-mat/0607095,
title = {Dynamics of Pinned Magnetic Vortices},
author = {R. L. Compton and P. A. Crowell},
journal= {arXiv preprint arXiv:cond-mat/0607095},
year = {2009}
}