Dresden 2006 – scientific programme
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MA: Magnetismus
MA 33: Spin-Dynamics, Magnetization Reversal III
MA 33.10: Talk
Thursday, March 30, 2006, 17:30–17:45, HSZ 403
Magnetization dynamics in all optical pump-probe experiments — •Marija Djordjevic1, J. Walowski1, A. Parge1, M. Münzenberg1, and J.S. Moodera2 — 1IV. Physikalisches Institut, Universität Göttingen — 2Francis Bitter Magnet Laboratory, MIT; Cambridge, USA
The study of magnetization dynamics on the femtosecond timescale is an important task for the implementation of future spintronics. In all optical pump-probe experiments the Ti:Sapphire laser pulses amplified with a regenerative amplifier (RegA 9000, 1 µ J pulse energy) are used to demagnetize a 50 nm Ni film and to follow the magnetization relaxation with 80 fs time resolution. Magnetization precession is triggered with a laser induced change in the anisotropy field. The demagnetization rate is controlled with the pump laser fluence. Different precession modes are observed in the range from 1.5 GHz up to 13 GHz. In the time-resolved spectrum an incoherent magnon background, a coherent homogeneous precession mode and a standing spin wave mode are observed. All those contributions are strongly dependent on the amplitude and the orientation of the external field as well as on the pump laser fluence. The corresponding Gilbert damping parameter is found to be dependent on the precession mode, taking values from α=0.05 for very low up to α=0.25 for highly damped modes. The parameter changes with the variation of the field angle, the field strength and the height of the excitation amplitudes. This indicates mode dependent energy dissipation and mode conversion mechanisms.