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MA: Magnetismus

MA 27: Spin-Dynamics, Magnetization Reversal II

MA 27.2: Vortrag

Donnerstag, 30. März 2006, 10:30–10:45, HSZ 403

Ultraslow femtosecond relaxation observed for high excitation power — •Markus Münzenberg, Marija Djordjevic, and Gerrit Eilers — IV. Phys. Inst., University of Göttingen

All-optical pump probe experiments give a unique insight into high nonequilibrium femtosecond timescale. A micromagnetic model using the OOMMF simulation code (NIST) is developed, to explain the significant increase of the relaxation times observed for high pump fluences larger 30 mJ/cm². After the restoration of the local spin magnetization, small random few nanometer sized domains are formed with an average net magnetization of zero. If the magnetization below the disturbed region remains unaffected by the pump pulse, the energy is dissipated by the emission of spin waves an decreases the restoration time of the magnetization. The effect is analogous to the increased non local Gilbert damping by the emission of spin waves that was found in earlier investigation of our group in the spot geometry. The investigation and understanding of these effects is of strong importance for the application of thermally-assisted writing in the new generation of hard disc heads.