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KR: Fachgruppe Kristallographie

KR 3: Crystallography - poster session

KR 3.3: Poster

Mittwoch, 22. März 2017, 18:00–20:00, P4

Watching the Verwey transition of Magnetite by Timeresolved X-Ray diffraction — •Alexander von Reppert¹, Jan-Etienne Pudell¹, Flavio Zamponi¹, Azize Koc², Stephan Geprägs³, Jose Emilio Lorenzo⁴, Luc Ortega⁵, Matthias Reinhardt², and Matias Bargheer^1,2 — ¹Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht Str. 24-25, 14476 Potsdam, Germany — ²Helmholtz-Zentrum Berlin BESSY II, Albert-Einstein Str. 15, 12489 Berlin, Germany — ³Walther-Meißner-Institut, Bayerische Akademie d. Wissenschaften, 85748 Garching, Germany — ⁴Institut Nèel, CNRS & Univ. Grenoble Alpes, 38042 Grenoble, France — ⁵Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay, France

We present timeresolved X-Ray diffraction from a 300 nm thin Magnetite(Fe3O4) film that is driven across the Verwey transition by fs-laser excitation. The prototypical insulator to metal transition at 123 K is accompanied by a peak intensity increase and peak width decrease of structural Bragg peaks, which we attribute to the destruction of trimerons that lead to inhomogeneous lattice strain in the low T phase. Our systematic investigations of the lattice dynamics yield two timescales: An ultrafast peak width drop - probably due to electronic processes - which is subsequently enhanced by transport and equilibration of the excitations. Complementary to our lab-based Plasma X-Ray source we conducted measurements at the XPP beamline at the synchrotron BESSY II where we observe that the recovery timescale depends crucially on the proximity to the transition temperature.