Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 27: Magnetization / Demagnetization Dynamics I
MA 27.1: Vortrag
Mittwoch, 18. März 2015, 09:30–09:45, EB 301
Towards probing ultrafast magnetization dynamics with a table top XMCD setup — •Felix Willems1, C T L Smeenk2, Clemens von Korff Schmising1, Oleg Kornilov2, Marc Vrakking2, and Stefan Eisebitt1 — 1TU Berlin, 10623 Berlin — 2Max-Born-Institut, 12489 Berlin
The understanding of ultrafast demagnetization dynamics is of high interest for future applications such as ultrafast magnetic switches and magnetic data storage. Up today there is evidence that two mechanisms (spin-flips [1] and spin transport [2,3]) drive the magnetic dynamics on the femtosecond time scale. In order to isolate the two mechanisms, we need an experimental setup that provides ultrafast time resolution, a well-defined magnetic contrast and element specific sensitivity. We have set up a HHG source that generates circularly polarized x-rays in the energy range of the M-edges of transition metals (40-70 eV) using a four mirror reflection-polariser. We report on first measurements exploiting x-ray magnetic circular dichroism to measure transient magnetisation changes in tailored thin film multilayer sample systems. The advantage of our approach lies in the simultaneous quantitative probing of magnetization of different elements in the sample, enabling us to determine the timing of the dynamics in the adjacent layers with sub 40 fs accuracy. We expect to quantify transport of spin-polarized electrons between the layers vs. dynamics caused by electron-phonon spin flip processes and report on first experiments towards this goal. [1] Koopmans et al., Nat. Mat. 9, 259 (2010) [2] Battiato et al., PRL 105, 027203 (2010) [3] Pfau et al., Nat.Comm. 3, 1100 (2012)