Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 19: Poster I (Bio- and Molecular Magnetism/ Magnetic Particles and Clusters/ Micro- and Nanostructured Magnetic Materials/ Magnetic Materials/ Multiferroics/ Magnetic Shape Memory Alloys/ Electron Theory of Magntism/ Spincaloric Transport/ Magnetic Coupling and Exchange Bias/ Magnetization Dynamics/ Micromagnetism and Computational Magnetics)
MA 19.93: Poster
Dienstag, 15. März 2011, 10:45–13:00, P2
Magnetization dynamics described via a thermal mechanism — •Martin Lüttich1, Jakob Walowski1, Andreas Mann1, Markus Münzenberg1, Unai Atxitia2, and Oksana Chubykalo-Fesenko2 — 1I. Physikalisches Institut, Universität Göttingen — 2Instituto de Ciencia de Materiales de Madrid
Magnetization dynamics of polycrystalline nickel films with thicknesses of 2, 5, 10, 15, 20 and 40 nm is measured using the all-optical pump-probe technique. The theoretical description of the microscopic processes in these dynamics has the challenge and complexity of the parallel treatment of photons, electrons, phonons and magnetic correlation of the system. Additionally different length and time scales are involved.
We access these processes via a thermal model derived from the Landau-Lifshitz-Bloch equation. Within this approach it is assumed that the excited state is a statistical ensemble of many spin excitations. First the electron temperature is extracted via a 2 Temperature model from reflectivity measurements, and later used to model the magnetization dynamics. Because of the strong electron-spin coupling in transition metals, we find that the magnetisation dynamics is defined by the electron temperature but is slowed down with respect to the electron temperature due to the slowing down of the longitudinal relaxation defined by the exchange interactions. We discuss the effects for thinest Ni layers below 10 nm where the demagnetization deviates from the simple scaling for fluence and thickness.