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MA: Fachverband Magnetismus
MA 20: POSTER Ib
MA 20.5: Poster
Tuesday, March 17, 2015, 09:30–13:00, Poster A
Ultrafast Magnetostriction of Antiferromagnetic Holmium studied by Femtosecond X-ray Diffraction — •Jan-Etienne Pudell1, Alexander von Reppert1, Flavio Zamponi1, Matthias Rössle1, Daniel Schick2, and Matias Bargheer1,2 — 1Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany — 2Helmholtz-Zentrum Berlin, Wilhelm-Conrad-Röntgen Campus, BESSY II, Albert-Einstein-Str. 15, 12489 Berlin, Germany
We present time-resolved X-ray diffraction on a Holmium thin film after femtosecond laser excitation. The lattice shows rich spatio-temporal dynamics, where the contraction and expansion are driven by the excitation of electrons, magnons and phonons.
The indirect exchange interaction (RKKY) in the 80 nm Holmium film leads to an incommensurate helical antiferromagnetic (AFM) spin structure below the Néel temperature of approx. 131 K. The strong magnetostriction in Holmium results in an decrease of the lattice constant with temperature. The sub-pico to nanosecond lattice dynamics after photoexcitation are studied by ultrafast X-ray diffraction (UXRD) using a laser-driven Plasma X-ray Source (PXS). The sample is excited with 800 nm femtosecond laser pulse of different fluences starting at various temperatures below and above the Néel temperature of Holmium. The phonon driven lattice expansion takes place within 15 ps and is sound velocity limited. Below the Néel temperature, the heating of the magnetic system induces an ultrafast magnetostriction, which leads to a contraction within 25 ps.