Dresden 2014 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 29: Magnetization Dynamics II
MA 29.9: Vortrag
Mittwoch, 2. April 2014, 17:15–17:30, HSZ 401
Gilbert damping tensor within the breathing Fermi surface model: anisotropy and non-locality — •Danny Thonig1,2 and Jürgen Henk2 — 1Max Planck Institute of Microstructure Physics, Halle, Germany — 2Martin Luther University Halle-Wittenberg, Halle, Germany
An essential property of magnetic devices is the relaxation rate in magnetic switching which depends strongly on the damping in the magnetization dynamics. The latter enters the Landau-Lifshitz-Gilbert equation as Gilbert damping α and is commonly taken as a phenomenological parameter. Recent experiments predict, however, a complicated behavior of dissipation in low-dimensional systems, which is hardly to explain by a local scalar α. This mismatch calls for a theoretical understanding based on ab initio results.
We apply the breathing Fermi surface model [1] in the framework of a renormalized Green function tight-binding approach. Slater-Koster parameters were obtained by genetic-algorithm optimization with respect to first-principles results. Magnetic as well as structural disorder are treated by the coherent potential approximation. The results are non-local Gilbert tensors αij which depend on the electron, spin and phonon temperatures as well as on the directions of the local magnetic moments.
Our approach is applied to the bulk and to surfaces of Stoner magnets. The non-local tensorial behavior of the damping leads to significant differences with respect to the conventional local scalar treatment.
[1] V. Kamberský. Cz. Journal of Physics B, 34 (1984) 1111