Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 9: Micromagnetism/Computational Magnetics

MA 9.1: Vortrag

Montag, 25. Februar 2008, 16:45–17:00, H 1012

Magnetic Contribution to Friction — •Martin P. Magiera and Dietrich E. Wolf — Department of Physics, University of Duisburg-Essen, 47048 Duisburg, Germany

We theoretically study the magnetic contribution to friction force by simulating an atomic anisotropic ferromagnetic Heisenberg system moving relative to a nanometer scaled extra spin. Interaction in between them is described by dipole interaction (cut off to avoid finite size effects). For integration of the dynamic system we use the Landau Lifshitz Gilbert equation. Langevin dynamics provide an insight into thermal effects. Friction force is calculated by derivation of energy dissipation terms and distinction of thermal and magnetic energy flow contributions.

We find a linear velocity dependence of the friction force, analogous to mechanical models like the Tomlinson model. Its slope is proportional to the phenomenological damping parameter in the Landau Lifshitz Gilbert equation, in agreement with the fluctuation dissipation theorem. Finally we find a nonzero friction and slope in the paramagnetic phase, as well as a rather complex friction force vs. velocity behavior at higher velocities. Hence we interpret the dissipation mechanism as an excitation of spin waves with a finite spectrum.