Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 26: Spin Dynamics / Spin -Torque II

MA 26.10: Vortrag

Donnerstag, 28. Februar 2008, 17:00–17:15, EB 301

Femtosecond magnetization dynamics of iron films after laser excitation — •Stefan Polei, Xuan Truong Nguyen, Armin Kleibert, and Karl-Heinz Meiwes-Broer — Institut für Physik, Universität Rostock, 18051 Rostock, Germany

In 1996 Beaurepaire et al. [1] demonstrated a femtosecond demagnetization of a ferromagnetic sample after excitation with ultrashort laser pulses. The observed time scale was approx. 100 times shorter than expected from theory of magnetization dynamics. Thus, this pioneering experiment has attracted much attention by researchers worldwide. Despite its enormous potential for applications, a full microscopic understanding is still lacking. Thus, great efforts are made to get insight into the fundamental physical processes which lead to a rapid loss followed by a slower recovery of the magnetization within the first picoseconds.

In this contribution we present recent pump-probe experiments on thin iron films. Our setup relies on a Ti-Saphire-laser followed by a multipath amplifier providing pulses of 35fs with up to 2.5mJ at 800nm and a repetition rate of 1kHz. The magnetization dynamics is investigated observing the magneto-optical Kerr-rotation in the longitudinal geometry. Time-dependent hysteresis loops obtained by varying the pump-probe delay give insight into the magnetization dynamics.

[1] Beaurepaire et al., PRL 76, 4250 (1996)