Dresden 2006 – wissenschaftliches Programm

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MA: Magnetismus

MA 33: Spin-Dynamics, Magnetization Reversal III

MA 33.12: Vortrag

Donnerstag, 30. März 2006, 18:00–18:15, HSZ 403

Ultrafast demagnetization dynamics of ferromagnetic materials — •Tobias Roth, Dorothea Hoffmann, and Martin Aeschlimann — Fachbereich Physik, TU Kaiserslautern, Erwin-Schrödinger Str.46, 67663 Kaiserslautern

The response of the magnetization to an ultrashort femtosecond laser pulse has been investigated by different techniques in the last decade but it still remains a highly controversial topic with respect to the involved microscopic processes. Up to now most of the investigations were based on ultrathin samples like Ni or CoPt3 with a low Curie temperature. The availability of very intense laser pulses delivered from a multipass amplifier system of 1 kHz repetition rate provides the experimental precondition to do time resolved measurements on Co, the material with the highest Curie point among the 3d transition metals. We apply the longitudinal MOKE in a bi-chromatic pump-probe technique to obtain a time resolved response of the magnetic system. By choosing a different wavelength for the pump and probe the well known No-dqbleachingNo-dq, an optical effect - caused by a change in the occupation number in a highly non equilibrium state - can be suppressed; therefore we have access to the pure magnetization. Our results exhibit a distinct demagnetization effect of around 50 % which is reached 750 fs after the pump pulse has impinged on the sample.