Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)
MA 15.35: Poster
Dienstag, 27. März 2007, 15:00–19:00, Poster A
Current-induced magnetic vortex dynamics: micromagnetic simulations and time-resolved x-ray microscopy — •A. Drews1, M. Bolte1, B. Krüger2, G. Meier1, U. Merkt1, B. Van Waeyenberge3, A. Puzic4, K. W. Chou4, and H. Stoll4 — 1Institut für Angewandte Physik, 20355 Hamburg. — 2I. Institut für Theoretische Physik, 20355 Hamburg — 3Department of Subatomic and Radiation Physics, Ghent University, 9000 Gent, Belgium — 4Max-Planck-Institut für Metallforschung, 70569 Stuttgart
We investigated the current-driven vortex and antivortex dynamics in permalloy rectangles by time-resolved x-ray microscopy and micromagnetic simulations. Experimentally, the vortex rotation was excited by electric ac currents passing directly through the samples. The dynamics was observed by time-resolved x-ray microscopy at beamline 11.0.2. at the Advanced Light Source in Berkeley. From the direction of gyration of the vortices, we determine the polarization of the vortices and the phase of the rotation. We show that in the present experiments only the spin torque and not the Oersted field causes the vortex rotation. We also observe the current-induced rotation of an antivortex at higher frequencies. Micromagnetic simulations were performed for the samples’ geometries with OOMMF, extended by the spin-torque term of Zhang and Li. From the simulations we deduce the eigenfrequencies of the vortex motion. We find that two vortices and one antivortex are excited to rotation in a 2x3 µ m2 permalloy rectangle, in agreement with the experiments. Simulations with higher current densities yield a flipping of the polarization of both vortices and antivortex.