Regensburg 2010 – scientific programme
Parts | Days | Selection | Search | Downloads | Help
MA: Fachverband Magnetismus
MA 33: Poster II
MA 33.78: Poster
Friday, March 26, 2010, 11:00–14:00, Poster B1
Ultrafast Demagnetization in Heisenberg Ferromagnets — •Marko Wietstruk1, Torsten Kachel1, Niko Pontius1, Christian Stamm1, Hermann A. Dürr1, Wolfgang Eberhardt1, Cornelius Gahl2, Martin Weinelt2,3, Alexey Melnikov3, and Uwe Bovensiepen4 — 1Helmholtz-Zentrum Berlin, BESSYII — 2Max-Born-Institut Berlin — 3Freie Universität Berlin, FB Physik — 4Universität Duisburg-Essen, FB Physik
Gd and Tb are typical Heisenberg ferromagnets, consisting of RKKY-coupled localized 4f moments and polarized 5d valence electrons. In our time-resolved x-ray magnetic circular dichroism (TR-XMCD) experiment we excite the valence electrons with a 50 fs laser pulse and probe the 4f moment using 100 fs x-ray pulses from the BESSY II femtoslicing source.
In Gd we found two distinct demagnetization processes. The first, occurring on a 1 ps timescale, coincides with the relaxation of hot electrons via electron-phonon scattering. This supports the theory of demagnetization via Elliott-Yafet type spin-flip scattering [1]. As the process persists much longer than the laser pulse, a demagnetization by coherent laser excitation is unlikely [2]. The second process with a time constant of 40 ps in Gd is attributed to spin-lattice relaxation [3]. In Tb we found a much faster time constant of <5 ps, as expected from theory [3].
[1] B. Koopmans et al., PRL 95, 267207 (2005)
[2] G.P. Zhang & W. Hübner, PRL 85, 3025 (2000)
[3] W. Hübner & K.H. Bennemann, PRB, 53, 3422 (1996)