Dresden 2009 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
MA: Fachverband Magnetismus
MA 19: Micro Magnetism / Computational Magnetism
MA 19.6: Vortrag
Mittwoch, 25. März 2009, 11:30–11:45, HSZ 403
Magnetic friction and “turbulence” at ferromagnetic surfaces — •Martin Magiera1, Lothar Brendel1, Dietrich E. Wolf1, and Ulrich Nowak2 — 1Department of Physics, University of Duisburg-Essen, D-47058 Duisburg, Germany — 2Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
We theoretically study the magnetic contribution to friction force by simulating a ferromagnetic Heisenberg system scanned by a magnetic tip represented by a dipole field. The spin dynamics is given by the Landau-Lifshitz-Gilbert equation including a stochastic term describing thermal fluctuations. Friction force is calculated from energy dissipation terms, where thermal and magnetic energy flow contributions have to be distinguished.
For small velocities the friction force depends linearly on the scanning velocity, as well as on the phenomenological damping constant. This so-called laminar regime is in perfect agreement with our findings from a macrospin-model. Above a certain velocity vortices may occur, which propagate in the system – which is now called turbulent. Here the friction force measured is no more viscous, and its correlation with the occurence and propatation of vortices is studied.
ACKNOWLEDGEMENT: This work was supported by the German Research Foundation (DFG) via SFB 616. Computation time was granted by the John-von-Neumann-Institute of Computing (NIC) in Jülich.