Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 27: Spindynamik II

MA 27.1: Vortrag

Dienstag, 8. März 2005, 15:15–15:30, TU H1012

Micromagnetic Dissipation, Dispersion and Mode Conversion in thin Permalloy platelets — •Matthias Buess^1,2, Thomas Haug¹, Michael R. Scheinfein³ und Christian H. Back¹ — ¹Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93040 Regensburg, Germany — ²Laboratorium für Festkörperphysik, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland — ³Simon Fraser University, 8888 University Drive, Burnaby BC U5A 156, Canada

Micron sized ferromagnetic permalloy disks exhibiting an in-plane ferromagnetic vortex structure are excited by a fast rise time perpendicular magnetic field pulse and their modal structure is analyzed. We find azimuthal and axial modes. By a fourier filtering technique we can separate and analyze the time dependence of individual modes. Analysis of the experimental data demonstrates that the azimuthal modes damp more quickly than the axial modes. We interpret these results as mode conversion from low-frequency azimuthal modes to the fundamental mode which is higher in frequency, i.e. mode-mode coupling in a system with a single Landau-Lifshitz-Gilbert phenomenological damping constant. We present a method to extract the decay rates for different modes from a single average precession component. These measurements are the first clear demonstration that mode-mode coupling plays a significant role in magnetization dynamics, and, the data demonstrate how mode-conversion could be construed as damping.