Regensburg 2013 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Magnetization Dynamics I of 3

MA 33.7: Talk

Thursday, March 14, 2013, 11:00–11:15, H22

Ultrafast spin dynamics in epitaxial Co/Cu(001) analyzed by femtosecond time-resolved linear and non-linear magneto optics — •Jens Wieczorek, Nicolas Bergeard, Alexander Tarasevitch, and Uwe Bovensiepen — Universität Duisburg-Essen, Fakultät für Physik, 47057 Germany

In order to investigate the microscopic processes in laser-induced demagnetisation, we performed pump probe measurements at Co/Cu(001)films at thicknesses 5 ML<d<30 ML. We used simultaneously time resolved magneto-optical Kerr effect(MOKE)and magneto induced second harmonic generation (MSHG) in a transversal geometry. The transient nonlinear MSHG signal is essentially independent on thickness, whereas the linear MOKE signal shows an increasing pump induced demagnetisation Δ M and an increase in the demagnetization time for larger d. Since MSHG is generated at the films interfaces and MOKE probes the film as a whole we conclude from the observed thickness dependence that different mechanisms contribute to the laser- induced change of the magnetization. At smallest d transport contributions might represent the dominant channel[1,2], while for larger d also slower, local processes like angular momentum transfer to phonons[3] become relevant.

We acknowledge support by the DFG through SFB616. [1] M. Battiato et al., PRL 105, 027203 (2010) [2] A. Melnikov et al., PRL 107, 076601 (2011) [3] Koopmans et al., Nat Mat 9, 259 (2010)