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MA: Magnetismus

MA 18: Spin-Dynamics, Magnetization Reversal I

MA 18.1: Talk

Tuesday, March 28, 2006, 10:15–10:30, HSZ 403

Modal Spectrum of Permalloy Disks with and without Vortex — •Frank Hoffmann, Korbinian Perzlmaier, Georg Woltersdorf, Ingo Neudecker, and Christian Back — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg

The mode spectrum of micron-sized ferromagnetic permalloy disks, exhibiting a vortex ground state, was investigated. In equilibrium the magnetization is in the plane of the sample, except for a small region in the center, where it is aligned perpendicular.
Time resolved scanning Kerr microscopy was used to measure the temporal evolution of the magnetization after application of a fast rise time in-plane field pulse. Spatially resolved amplitude and phase spectra reveal the mode structure, that consists of modes with circular nodes and modes with diametric nodes.
It is shown, that the lowest order azimuthal mode, a mode with only one diametric node, splits into a doublet as the disk diameter decreases. Ivanov and Zaspel [1] have shown theoretically, that this splitting is due to interaction with the gyrotropic motion of the vortex core. By removing the vortex core the splitting of the modes vanishes. This behaviour was found both in micromagnetic simulations and experiments.
PRL 94, 027205 (2005)