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MA: Fachverband Magnetismus
MA 34: Magnetization / Demagnetization Dynamics III
MA 34.5: Vortrag
Mittwoch, 28. März 2012, 16:00–16:15, H 1012
Electron- and phonon-mediated ultrafast magnetization dynamics of Gd — •M. Sultan1,2,3, A. Melnikov2,4, U. Atxitia5, O. C. Fesenko5, and U. Bovensiepen1 — 1Fakult. Phys., Uni. Duisburg-Essen — 2Fach. Phys., Freie Uni. Berlin — 3National Cent. Phys., Islamabad — 4Phys. Chem., FHI, Berlin — 5Inst. Cienc. Mater., Madrid
Disentangling different microscopic contributions in ultrafast magnetization dynamics is a challenging task. As a potential system to resolve this, Gd exhibits a two step demagnetization with characteristic time scales of 0.75 ps and 40 ps related to the non-equilibrium and a quasi-equilibrium regimes, respectively [1]. Here we report on the temperature dependent ultrafast magnetization dynamics of Gd(0001), which was investigated by employing the fs time-resolved magneto-optical Kerr effect and modelling by the Landau-Lifshitz-Bloch equation. The demagnetization time determined from the experiment increases with temperature from 0.8 ps at 50 K to 1.5 ps at 280 K. A successful theoretical description of this observation was achieved by considering that the localized 4f spin system is affected by two contributions: coupling to the 5d fraction through (a) electronic scattering processes and (b) spin-flip scattering mediated by phonons. We conclude that at temperatures below the Debye temperature a hot electron-mediated process describes the experimentally found demagnetization times well. At higher temperatures phonon-mediated processes have to be included in addition to explain the two times longer demagnetization time.
[1] Wietstruk et al., PRL 106, 127401 (2011)