Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 38: Magnetization Dynamics IV
MA 38.2: Vortrag
Mittwoch, 16. März 2011, 15:00–15:15, HSZ 403
Controlled Vortex Core Reversal by Excitation of Spin Wave Modes — •Matthias Kammerer1, Markus Weigand1, Michael Curcic1, Matthias Noske1, Markus Sproll1, Hermann Stoll1, Bartel Van Waeyenberge2, Georg Woltersdorf3, Christian H. Back1, and Gisela Schütz3 — 1MPI für Metallforschung, Stuttgart — 2Ghen University, Belgium — 3Universität Regensburg
It is well known, that magnetic vortex core reversal can be achieved by excitation of the (sub-GHz) vortex gyromode [1,2]. Surprisingly our experiments and micromagnetic simulations show an unidirectional vortex core switching by excitation of magneto static spin waves at frequencies more than an order of magnitude higher. These results were obtained with time-resolved magnetic imaging at the scanning X-ray microscope MAXYMUS at BESSY II, Berlin. Circular Permalloy platelets have been excited with in-plane rotating magnetic field bursts at GHz frequencies. Imaging could be performed with 30 ps time resolution. Vortex state structures possess spin wave eigenmodes arising from the magneto-static interaction. The interaction between these modes and the gyrotropic mode breaks the cylindrical symmetry of the micromagnetic objects, leading to a frequency splitting of the spin wave modes with opposite rotation senses. We could demonstrate [3] that the unidirectional vortex core reversal process is not limited to the gyrotropic mode but is a general mechanism when azimuthal modes (with m = +/- 1) are excited. [1] B. Van Waeyenberg et al., Nature 444, 461 (2006) [2] M. Curcic et al., PRL 101, 197204 (2008) [3] M. Kammerer et al., http://arxiv.org/abs/1008.4719