Berlin 2008 – scientific programme

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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 18.72: Poster

Tuesday, February 26, 2008, 15:15–18:30, Poster E

Current-induced domain-wall and vortex motion — •Thomas Kamionka¹, Michael Martens¹, Stellan Bohlens², Toru Matsuyama¹, Ulrich Merkt¹, and Guido Meier¹ — ¹Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiustr. 11, 20355 Hamburg, Germany — ²I. Institut für Theoretische Physik, Universität Hamburg, Jungiustr. 9, 20355 Hamburg, Germany

The interaction of spin-polarized currents with the magnetization of a ferromagnet opens new opportunities to design magnetic memory and logic devices. We investigate the harmonic excitation of a vortex in a square permalloy thin-film element with spin-polarized currents. A rotation of the vortex around its equilibrium position has been predicted [1]. The experimental challenge is to design a square with a low resonance frequency of the vortex, i.e. a weak confining potential, and to ensure the existence of the vortex state. The low resonance frequency is obtained for a small ratio t/l of thickness t and width l. We analyze the micromagnetic behavior of our permalloy squares by magnetic-force microscopy and the anisotropic magnetoresistance (AMR). Supported by micromagnetic simulations, we can determine possible magnetization patterns. A current induced excitation increases the electrical resistance because of the energy dissipation [2] and should be measurable using a LCR-Tester and scalar network analysis.

[1] B. Krüger et al., Phys. Rev. B accepted.

[2] E. Saitoh et al., Nature 432, 203 (2004).