Berlin 2012 – scientific programme
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MA: Fachverband Magnetismus
MA 34: Magnetization / Demagnetization Dynamics III
MA 34.2: Talk
Wednesday, March 28, 2012, 15:15–15:30, H 1012
Switching the magnetic vortex core by combined gyromode and spin wave excitation. — •Markus Sproll1, Matthias Kammerer1, Markus Weigand1, Matthias Noske1, Ajay Gangwar2, Georg Woltersdorf2, Hermann Stoll1, and Gisela Schütz1 — 1MPI for Intelligent Systems, Stuttgart — 2Department of Physics, Regensburg University
The vortex core (VC) in micron sized Permalloy platelets can be switched by exciting (i) the sub-GHz vortex gyromode [1] or (ii) multi-GHz azimuthal spin wave modes [2]. We have combined these two excitation schemes at significantly different frequencies and it was found that the switching threshold (i.e., the amplitude of the GHz rotating in-plane magnetic field) needed for spin wave mediated VC reversal is reduced by up to 30 % depending on the amplitude of an additional linear in-plane ac magnetic field at the sub-GHz gyromode eigenfrequency. Experiments have been performed by time-resolved measurements at the MAXYMUS (STXM) endstation at BESSY. Movies have been taken, starting with the excitation of the VC by a gyrotropic vortex gyration before a CW or CCW rotating spin wave mode was excited simultaneously with the gyromode. Finally only the VC gyration is excited again showing in case of polarity switching by the spin wave a reversed sense of rotation. All these experimental findings are in good agreement with micromagnetic simulations. A physical explanation for the reduced switching thresholds will be discussed as well as spintronic applications. [1] B. Van Waeyenberge et al., Nature 444, 461(2006) [2] M. Kammerer et al., Nature Communications 2, 279(2011)