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MA: Fachverband Magnetismus

MA 52: Poster II

MA 52.34: Poster

Thursday, March 15, 2018, 15:00–18:00, Poster C

Energy flow in the rare earth Dysprosium revealed by Ultrafast X-Ray diffraction — •Alexander von Reppert¹, Jan-Etienne Pudell¹, Azize Koc², Karine Dumesnil³, Matthias Reinhardt², Flavio Zamponi¹, and Matias Bargheer^1,2 — ¹Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany — ²Helmholtz-Zentrum Berlin, Berlin, Germany — ³Institut Jean Lamour (UMR CNRS 7198), Université Lorraine, Nancy, France

We present ultrafast x-ray diffraction (UXRD) measurements on nanolayered Dysprosium systems, that serves as a model for the class of heavy rare earth materials (Ho, Gd, Tb, ..), which exhibit large magnetostriction. We excite the material by femtosecond light pulses, which instantaneously heat up the electron gas. The coupling of the deposited energy to spin degrees of freedom and to phonons yields the lattice strain. The measured strain is a result of two stress components acting on the atoms: The stresses due to phonons and spins are proportional to the energies in the phonon and spin systems via effective Grüneisen constants which have opposite signs in these rare earths. By a careful analytic decomposition of the signals we can monitor the heat flow among spins and phonons and observe a long lasting non-equilibrium between the spin and phonon excitations that persists for many nanoseconds.