Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 26: Micromagnetism / Computational Magnetics

MA 26.1: Vortrag

Mittwoch, 28. März 2012, 10:45–11:00, H 0112

Multiscale simulation of micromagnetic singularities — •Christian Andreas^1,2, Attila Kákay¹, Ming Yan¹, and Riccardo Hertel^1,2 — ¹Peter Grünberg Institut, Electronic Properties, Forschungszentrum Jülich GmbH — ²IPCMS, CNRS UMR 7504, Strasbourg, France

Several fundamental processes like bubble domain reversal and vortex core switching include the formation of Bloch points (BP) [1,2,3]. Such micromagnetic singularities pose limits to the validity of micromagnetic simulations and are usually treated within the realm of micromagnetism by using mesh refinement and extrapolations to zero-mesh size. The problem is the singularity of the exchange energy density for BPs. A more realistic description is obtained by employing a multiscale model, which removes this singularity. We present a multiscale approach combining our micromagnetic code TetraMag with a Heisenberg model. This allows us to treat the exchange energy around BPs atomistically, by taking into account 10⁶ atoms. The multiscale code exploits the computational power of Graphical Processing Units, thereby allowing us to extend the dynamic calculation to several nanoseconds on the micrometer length scale. The results elucidate to which extent BPs can be treated reliably with standard micromagnetic simulations. It is shown that the intrinsic overestimation of the BP energy of the continuum approximation is generally not counterbalanced by discretization effects which systematically underestimate it. [1] Hertel, R. et al., Phys. Rev. Lett. 98, 117201 (2007) [2] Thiaville, A. et al., Phys. Rev. B 67, 094410 (2003) [3] Döring, W. J. Appl. Phys. 39, 1006 (1968)