Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 30: Spin-Dynamics / Spin-Torque III
MA 30.8: Vortrag
Donnerstag, 26. März 2009, 12:00–12:15, HSZ 04
Tailoring the Gilbert damping coefficient in Permalloy thin films by Ho doping — •Jakob Walowski1, Benjamin Lenk1, Andreas Mann1, Henning Ulrichs1, Stephen Krzyk2, Mathias Kläui2, and Markus Münzenberg1 — 1Physikalisches Institut, Universität Göttingen, Germany — 2Fachbereich Physik, Universität Konstanz, Gemany
The implementation of spintronics requires well-funded knowledge of the speed limits regarding magnetic switching. We use all-optical pump-probe experiments to explore the dynamics of 20 nm permalloy thin films triggered by strong Ti:Sa laser pulses (30 mJ/cm2, 60 fs) on two timescales after demagnetization. The fast demagnetization after excitation within the first 100−250 fs and the subsequent spin relaxation on a timescale up to 1 ns. It is generally described by the Landau-Lifshitz-Gilbert equation, from which the Gilbert damping parameter α can be extracted. Doping ferromagnetic materials with impurities in low concentrations can influence the intrinsic damping parameter (α(Py)=0.008), as has been shown using transition metal (Pd) and rare earth impurities (Dy) in concentrations up to 2% in our group. Here we extend of our study, using the rare earth Ho as an impurity dopant. It shows a stronger increase of α, for the same percentage of dopant than Dy. According to the model by Koopmans, the demagnetization time should be inversely proportional to α which doen not necessarily have to agree for the Ho doped samples, because of different dissipation channels in the rare earth impurities. Support by the DFG within the priority program SPP 1133 is gratefully acknowledged.