Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 8: Spindynamik I

MA 8.9: Vortrag

Freitag, 4. März 2005, 17:15–17:30, TU H1028

Excitations with negative dispersion in a spin vortex — •Matthias Buess^1,2, Tuomas P. J. Knowles², Rainer Höllinger¹, Thomas Haug¹, Uwe Krey¹, Dieter Weiss¹, Danilo Pescia², Michael R. Scheinfein³, and 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

Thin-circular lithographically defined magnetic elements with a spin vortex configuration are excited with a short perpendicular magnetic field pulse. The excited modes are imaged using time resolved magneto-optic Kerr microscopy and Fourier transformation. We extract the excitation spectrum from platelets ranging from 1 to 6 micron diameter and 15 nm thickness. Two types of modes are observed: radially symmetric modes with circular nodes and symmetry breaking modes with diametric nodes. The frequency of the modes with circular nodes increases with the number of nodes. In contrast, the frequency of the modes with diametric nodes decreases with the number of nodes. This behaviour is explained accurately by an analytical model. The model reproduces this phenomenon by considering the magnet-ostatic energy associated with the excited modes as suggested by Fletcher and Kittel more than 40 years ago ( P. C. Fletscher and C. Kittel, Phys. Rev. 120, 2004 (1960) ).