Dresden 2014 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 43: Magnetization Dynamics III
MA 43.12: Vortrag
Donnerstag, 3. April 2014, 18:00–18:15, HSZ 401
A sensor layer to magnify the magnetic vortex core polarization — •Georg Dieterle1, Joachim Gräfe1, Matthias Noske1, Markus Sproll1, Ajay Gangwar1,2, Markus Weigand1, Hermann Stoll1, Georg Woltersdorf2, Christian H. Back2, and Gisela Schütz1 — 1MPI for Intelligent Systems, Stuttgart, Germany — 2Department of Physics, Regensburg University, Germany
Sophisticated techniques like synchrotron based X-ray microscopy have to be used for imaging the vortex core (which can point either up or down) in magnetic vortex structures. We show how to magnify the vortex core magnetization to a diameter in the micrometer range in order to detect its polarization with magneto-optical Kerr effect (MOKE) microscopy. This can be achieved by a GdFe multilayer with out-of-plane magnetization and very low coercivity on top of a Permalloy vortex structure. The vortex core in the Permalloy disc is switched unidirectionally by a rotating RF magnetic field burst at the gyromode frequency of the vortex structure (about 570 MHz in our samples) with an amplitude A and a duration L. The reversal of the vortex core polarization by this RF burst also causes a defined reversal of the out-of-plane magnetization of the whole GdFe layer, 500 nm in diameter, which now can be easily detected by MOKE microscopy. Therefore, the GdFe layer acts as a sensor layer to magnify the polarization of the tiny vortex core. Experimental data are reported on the amplitude A and the duration L of the rotating RF fields necessary to switch both, (i) the vortex core polarization in the Permalloy disc and (ii) the magnetization of the whole GdFe disc above the vortex structure.