Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 27: Magnetization / Demagnetization Dynamics I
MA 27.8: Vortrag
Mittwoch, 18. März 2015, 11:30–11:45, EB 301
Time-resolved X-ray diffraction on dysprosium thin films — •Azize Koc1, Matthias Reinhardt1, Peter Gaal1,2, Wolfram Leitenberger3, and Matias Bargheer1,3 — 1Helmholtz Zentrum Berlin, BESSY II, Germany — 2Institute for Nanostructure and Solid State Physics, University of Hamburg, Germany — 3Institute of Physics and Astronomy, University of Potsdam, Germany
Dysprosium is a rare earth metal with a ferromagnetic (FM) phase below 86K and an antiferromagnetic (AFM) phase with a helical spin structure below 178 K [1].An important property of the antiferromagnetic phase is the negative thermal expansion coefficient due to magnetostrictive forces [2]. To investigate the structural changes and the interactions between electronic, phononic and magnonic degrees of freedom we use time-resolved X-ray diffraction at the XPP-KMC3 beamline at BESSY II.We feed energy into the conduction band electron system by excitation with 250 fs laser pulses at a central wavelength of 1030 nm.The structural response of the Dy thin film is measured with 100 ps time-resolution at temperatures from 100 K to 300 K and at various fluences. Above the AFM phase transition a fast lattice expansion according to the excitation of the phonon occurs (thermal expansion).Below the AFM phase transition a lattice contraction due to the rapid loss of the RKKY interaction is detected.We observe that the phonon system approaches equilibrium by heat conduction faster than 100 ns required to reestablish the antiferromagnetic order of the magnon system. [1] F.J. Darnell,Phys. Rev.,130,5 (1963) [2] M. Doerr, M. Rotter and A.Lindbaum, Adv. in Phy.,54:1, 1-66 (2005)