Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 18: Poster I : Bio Magn. (1-2); Mag.Imgaging (3-9); Magn. Semiconductors (10-16); Half Metals & Oxides (17-20); Coupl.Phenomena (21-27); Magn. Mat. (28-41); Micro & Nanostr. Magn. Materials (42-61); Micro Magn. (62-64); Surface Magnetism (65-70); Transport Phenomena (71-85)

MA 18.46: Poster

Dienstag, 26. Februar 2008, 15:15–18:30, Poster E

Preparation of anti-vortex configurations in Permalloy micromagnets — •Christian Dietrich, Christian Back, and Josef Zweck — Institut für Experimentelle und Angewandte Physik der Universität Regensburg, Germany

Permalloy magnets with lateral dimensions in the micron range or below show several (quasi)-stable magnetic configurations depending on thickness, precise shape and size. The static and dynamic properties of single-domain and vortex configurations are numerously published. On the way to do current-induced anti-vortex excitations we investigate how to experimentally prepare a preferably single anti-vortex. In general anti-vortex configurations in patterned magnetic films are characterised by a local energy minimum and only for specific shapes or dimensions these configurations reach an absolute energy minimum. The energy landscapes were studied by micromagnetic simulations. Rectangles with a particular aspect ratio and thickness show an anti-vortex configuration as most stable state in remanence. Micromagnetic simulations were also used to optimize the shape of the micromagnets to enhance the probability for the creation of an anti-vortex in remanent state for a given direction of the saturating magnetic field. To verify the simulations we investigated Permalloy rectangles with a constant width of 1 micron and different thicknesses and lengths by Lorentz transmission electron microscopy using the Fresnel mode, which allows a fast and simultaneous evaluation of many rectangles. Different magnetic configurations can be observed, with their frequency related to the energy distribution.