Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 33: Spindynamics / Switching III
MA 33.3: Vortrag
Freitag, 30. März 2007, 11:30–11:45, H23
Ultrafast demagnetization dynamics in Fe, Co, and Ni films observed by THz emission spectroscopy — •Jan Nötzold, Tobias Kampfrath, Christian Frischkorn, and Martin Wolf — Freie Universität Berlin, Arnimalle 14, 14195 Berlin
The excitation of ferromagnetic thin films with ultrashort laser pulses results in an ultrafast drop of the magnetization, which is accompanied by the emission of electromagnetic radiation in the THz frequency range [1]. In our work, we excite 10nm thick ferromagnetic films of Fe, Co, and Ni with intense laser pulses (∼ 1 mJ cm−2 fluence, 20fs duration, 800nm center wavelength) and measure the subsequently emitted radiation in the frequency window from 0.5 to 40 THz. The electric field is directly detected in the time domain via free-space electro-optic sampling. We discuss the origin of the emitted THz pulse and its relationship to the magnetization dynamics of the sample. No frequency components are found above 10 THz, which indicates that the laser induced demagnetization takes place on time scales larger than ∼ 100 fs.
[1] E. Beaurepaire, G. M. Turner, S. M. Harrel, C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, Appl. Phys. Lett. 84, 3465 (2004)