Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 35: Spin-Dynamics / Spin-Torque IV
MA 35.1: Vortrag
Donnerstag, 26. März 2009, 15:15–15:30, HSZ 04
Ultrafast Demagnetization of Lanthanide-Doped Permalloy Thin Films Studied with Time-Resolved Magneto-Optics — •Ilie Radu1,2, Matthias Kiessling1, Georg Woltersdorf1, Alexey Melnikov3, Uwe Bovensiepen3, Jan-Ulrich Thiele4, and Christian Back1 — 1Regensburg University, Regensburg, Germany — 2BESSY GmbH, Berlin, Germany — 3Free University Berlin, Berlin, Germany — 4Hitachi Global Storage, San Jose, CA, USA
The fs laser-induced magnetization dynamics of Permalloy thin films doped with Ho and Gd impurities is investigated by time-resolved magneto-optical Kerr effect. Varying the Ho concentration from 0% to 8% we observe a gradual change of the demagnetization time constant from approximately 60 fs to about 150 fs. In contrast, concentrations of Gd up to 15% do not affect the time scale of the demagnetization process. These results are at variance with recent theoretical work [1], that proposes a laser-induced demagnetization mechanism based on impurity- or phonon-assisted spin-flip scattering. We propose a demagnetization mechanism which relies on the strong magnetic inertia of the rare-earth dopant within the framework of the so-called slow relaxing impurity model [2,3].
[1] B. Koopmans et al., PRL 95, 267207 (2005); [2] J.H. van Vleck and R. Orbach, PRL 11, 65 (1963); [3] G. Woltersdorf et al., arXiv:0802.3206v2