Berlin 2012 – scientific programme
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MA: Fachverband Magnetismus
MA 34: Magnetization / Demagnetization Dynamics III
MA 34.9: Talk
Wednesday, March 28, 2012, 17:15–17:30, H 1012
Accessing the timescale of indirect exchange interaction in GdTb alloy by time-resolved x-ray spectroscopy — •Andrea Eschenlohr1, Alexey Melnikov2, Jens Wieczorek3, Nicolas Bergeard3, Christian Stamm1, Torsten Kachel1, Rolf Mitzner1, Karsten Holldack1, Marko Wietstruk4, Kristian Döbrich4, Martin Weinelt4,5, and Uwe Bovensiepen3 — 1Helmholtz Zentrum Berlin für Materialien und Energie GmbH — 2Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin — 3Universität Duisburg-Essen — 4Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin — 5Freie Universität Berlin
Time-resolved x-ray magnetic circular dichroism measurements on pure Gd and Tb show two-step demagnetization upon laser excitation [1], with different time constants for the second, slower process. In particular, this time constants depend on the strength of spin-lattice coupling, leading to a faster demagnetization in Tb, due to strong direct spin-lattice coupling, than in Gd. Here we investigate GdTb alloy, where the Gd 4f magnetic moments are coupled to the Tb 4f moments via indirect exchange interaction, resulting in an enhanced coupling of the Gd moments to the lattice. Indeed, we find that the Gd magnetic moments in GdTb alloy demagnetize faster than pure Gd. Looking at the element-specific magnetization dynamics on the femtosecond to picosecond timescale, we access the timescale of indirect exchange interaction between Gd and Tb magnetic moments in the alloy.
[1] M. Wietstruk et al., Phys. Rev. Lett. 106, 127401 (2011)