Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 19: Spin-Dynamics/Switching I
MA 19.1: Vortrag
Mittwoch, 28. März 2007, 15:15–15:30, H23
Observation of partial decoherence of quantized spin waves in nanoscaled magnetic ring structures — •Helmut Schultheiss1, Patrizio Candeloro1, Sebastian Schäfer1, Hans Nembach2, Britta Leven1, Andrei Slavin3, and Burkard Hillebrands1 — 1Fachbereich Physik and Forschungsschwerpunkt MINAS, TU Kaiserslautern, Germany — 2NIST, Boulder, Colorado, USA — 3Oakland University, Rochester, Michigan, USA
Nanoscale magnetic ring structures have recently attracted large attention due to their richness in magnetization structures. Not many investigations have been devoted to the spin waves in such elements and a full picture of the spin dynamics has not been emerged so far. Here we report on micro-focus Brillouin light scattering spectroscopy studies of the quantization mechanisms and in particular of the coherence of spin waves in 15 nm thick NiFe rings with varying diameters (from 1 to 3 µm). The magnetic excitations for both the vortex and the onion state were investigated. For the onion state several interesting effects were identified. First, in the pole regions spin wave wells are created due to the inhomogeneous internal field. Second, in the regions in between, modes with constant frequencies are observed only for the smallest structures, which are quantized in radial and azimuthal directions due to spatial coherence and confinement in the ring structure. For larger rings a continuous frequency variation with position is observed and is well reproduced by spin-wave calculations and micro-magnetic simulations. This work is supported by the DPG within the SPP1133 and the Japanese government within the NEDO project 2004IT093.