Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 26: Spin Dynamics / Spin -Torque II
MA 26.14: Vortrag
Donnerstag, 28. Februar 2008, 18:00–18:15, EB 301
Laser-Induced Magnetization Dynamics of Holmium-Doped Permalloy Thin Films — •Ilie Radu1,4, Matthias Kießling1, Georg Woltersdorf1, Alexey Melnikov2, Uwe Bowensiepen2, Jan Thiele3, Martin Wolf2, and Christian Back1 — 1Institut für Experimentelle Physik, Universität Regensburg — 2Fachbereich Physik, Freie Universität Berlin — 3Hitachi GST, San Jose Research Center, USA — 4BESSY GmbH, Berlin
The magnetization response of holmium-doped permalloy thin films after femtosecond laser excitation is studied by time-resolved magneto-optical Kerr effect (TR-MOKE). The investigated system consists of 10 nm Permalloy (Py) films doped with Holmium (Ho) at concentrations ranging from 1% to 8%. Consequently, the magnetization damping parameter changes from 0.008 (pure Py) to 0.2, as deduced from ferromagnetic resonance measurements. Thus, we can investigate the contribution of the impurity-assisted spin-flip scattering to the photo-induced demagnetization process. From the TR-MOKE data we observe: (i) a drop in the transient MOKE signal that evolves within the first hundreds of femtoseconds after optical excitation (ii) a gradual shift to longer pump-probe delays of the minimum position of the transient MOKE signal as the Ho impurity content increases. The results will be discussed along the lines of a recent theoretical model [1] which propose a laser-induced demagnetization mechanism determined by impurity- or/and phonon-mediated spin-flip scattering processes.
[1] B. Koopmans et al., PRL 95, 267207 (2005)