Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Magnetization / Demagnetization Dynamics I
MA 15.9: Vortrag
Dienstag, 27. März 2012, 12:00–12:15, H 1012
Ab-initio calculation of the demagnetization time in Ni after fs laser pulse excitation — •Christian Illg1, Bernd Meyer2, and Manfred Fähnle1 — 1Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart — 2Interdisziplinäres Zentrum für Molekulare Materialien und Computer-Chemie-Centrum, Universität Erlangen-Nürnberg
It is believed that an ultimate time limit for the macroscopic manipulation of the magnetization is achieved by exposing a ferromagnetic film to an intense sub-100 fs pulse of laser light [1]. The result of this exposure is a demagnetization within few 100 fs for Ni, e.g., and a subsequent remagnetization on a longer time scale. Since the first experiments by Beaurepaire et al. in 1996 [2] a lot of research activities have been done but the underlying mechanisms are still not clarified.
We calculate the demagnetization time T1 within the Elliott-Yafet theory which we have generalized for ferromagnets [3]. In order to calculate electron-phonon scattering rates, we use realistic electronic states which we calculate with the ab-initio spin-density-functional theory, and realistic phonon states obtained from a force-constant approach with force constants from ab-initio calculations. We present first results for the demagnetization time T1 within the generalized Elliott-Yafet theory for Ni.
M. Fähnle, C. Illg, J. Phys.: Condens. Matter 23, 493201 (2011)
E. Beaurepaire et al., Phys. Rev. Lett. 76, 4250 (1996)
D. Steiauf, C. Illg, M. Fähnle, J. Magn. Magn. Mater. 322, L5 (2010)