Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Magnetization / Demagnetization Dynamics I

MA 15.6: Vortrag

Dienstag, 27. März 2012, 11:00–11:15, H 1012

The influence of electron-phonon-scattering on the ultrafast demagnetization of ferromagnetic metals — •Sven Essert¹ and Hans Christian Schneider² — ¹Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany — ²Technische Universität Kaiserslautern, 67653 Kaiserslautern, Germany

The demagnetization of ferromagnetic metals after the irradiation with a femtosecond light pulse is believed to be decisively influenced by an Elliott-Yafet type process, i.e., by spin-flip scattering in a band structure which is spin-mixed due to spin-orbit coupling. There have been different proposals for the underlying scattering mechanism, e.g., electron-phonon-, electron-electron- or electron-impurity-scattering.

We numerically investigate the contribution of electron-phonon-scattering to the Elliott-Yafet demagnetization scenario in a fixed band structure by calculating the carrier-dynamics using ab-initio data. With realistic parameters for the laser excitation, we find a magnetization change which is far smaller than the one observed in experiment.

We also show via an energy argument, that the simple picture of scattering in a fixed band structure is insufficient to describe the experimentally observed strong demagnetization. This result is not limited to electron-phonon-scattering but is also valid for most other scattering mechanisms. We conclude that a realistic model that tries to explain the demagnetization in terms of an Elliott-Yafet process should include a dynamical change of the magnetic order beyond a redistribution of carriers in a fixed band structure.

[1] S. Essert and H.C. Schneider, arXiv:1108.4454 (2011)