Regensburg 2016 – scientific programme
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MA: Fachverband Magnetismus
MA 16: Magnetization and Demagnetization Dynamics I
MA 16.5: Talk
Tuesday, March 8, 2016, 10:30–10:45, H34
Imaging of Higher Order Gyromodes in Vortex Structures — •Johannes Förster1, Georg Dieterle1, Matthias Noske1, Ajay Gangwar2, Michael Vogel2, Hermann Stoll1, Markus Weigand1, Iuliia Bykowa1, Michael Bechtel1, Christian H. Back2, and Gisela Schütz1 — 1MPI für Intelligente Systeme, Stuttgart, Germany — 2Universität Regensburg, Germany
Magnetic vortex structures appear as ground states of the magnetization in suitable micron-sized ferromagnetic discs. These structures show a broad range of dynamic phenomena. Most basic is the fundamental gyromode where the vortex core gyrates around its equilibrium position with eigenfrequencies of a few hundred MHz. Resonant excitation of this mode causes the vortex core polarity to switch [1].
Besides this fundamental gyromode, higher order gyromodes were predicted in the GHz frequency range by micromagnetic simulations [2,3] and their frequencies were measured by FMR [3]. However, no imaging of such higher order gyromodes have been reported so far.
We will show movies of the first order gyromode in cylindrical Permalloy discs obtained by time-resolved scanning transmission X-ray microscopy. By resonant excitation of this mode switching of the vortex core polarity was observed. In addition, we started imaging the z-dependence of the flexure mode using sensor layers in our samples, by taking advantage of the element specificity of the XMCD effect.
[1] B. Van Waeyenberge, Nature 444, 461 (2006) [2] F. Boust and N. Vukadinovic, PRB 70, 172408 (2004) [3] J. Ding et al., Sci. Rep. 4, 4796 (2014)