Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 27: Magnetization / Demagnetization Dynamics I
MA 27.7: Vortrag
Mittwoch, 18. März 2015, 11:15–11:30, EB 301
Magnetostriction in Dysprosium studied by Ultrafast X-Ray diffraction — •Alexander von Reppert, Jan-Etienne Pudell, Flavio Zamponi, and Matias Bargheer — Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
We use ultrafast x-ray diffraction to study the lattice dynamics of thin film samples of dysprosium across a large temperature range with different magnetic ordering. Dysprosium has a phase transition from a paramagnetic to the antiferromagnetic phase at TNeel = 179 K and becomes ferromagnetic below TC = 86 K. A strong magnetostriction resulting from the RKKY - interaction in dysprosium leads to an anomalous increase of the interatomic distance with decreasing temperature. In our experiments, we study the behaviour of the dysprosium lattice after direct excitation of the electronic system in the dysprosium layer, as well as after an indirect excitation through electron and heat transfer from an excited adjacent yttrium layer. At temperatures below the phase transition hot electrons can not only couple to the phonon system, leading to an expansive stress but also interact with the magnetic system. Exciting the magnetic system affects the lattice potential so that we observe a contraction of the dysprosium lattice on the picosecond timescale on the order of 0.1%, which can be attributed to a partial removal of the repulsive RKKY interaction. From the fluence- and temperature-dependence we can study details of the coupling of electrons, phonons and magnetic excitation to extract relevant timescales.