Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 32: Postersession II: Spinstruct./Phase Trans. (1-10); Spinelectronics (11-15); Thin Films (16 - 36); Particles/Clusters (37-45); Multiferroics (46-54); Spindynamics/Spin Torque (55 - 76); Post Deadlines (77-79)

MA 32.58: Poster

Freitag, 29. Februar 2008, 11:15–14:00, Poster E

Femtosecond laser Kerr microscopy — •Jie Li, Min-Sang Lee, Wei He, Björn Redeker, and Thomas Eimüller — Junior Research Group Magnetic Microscopy, Ruhr-University Bochum, D-44780 Bochum, Germany

We present a new femtosecond laser Kerr microscope which has both scanning and full-field imaging capabilities. This instrument combines a lateral resolution in the sub-micrometer regime with a temporal resolution of better than 100 fs. The magnetic sample is thermally pumped by the fundamental beam and probed by the frequency-doubled beam via the magneto-optical Kerr effect (MOKE) in polar or longitudinal geometry. Double lock-in technique using a photo-elastic modulator (50 kHz) and an optical chopper (80 Hz) leads to very high sensitivity. In the scanning mode a three-axis piezo stage with a sub-nanometer resolution and 400 µm scan range in all directions is used. Full-field Kerr microscopy is possible by destroying the lateral coherence of the laser light with a rotating disc and detecting the image with a CCD camera. A cryostat allows measurements in the temperature range from 3.5 to 450 K. Instrument controlling software, developed on Visual Studio .Net, enables multi-dimensional scans, e.g., the MOKE signal can be recorded for arbitrary combination of six parameters (sample position, magnetic field, pump-probe delay time, and temperature). First time-resolved studies on Fe/Gd, Co/Ni and Co/Pt multilayer systems will be presented.

Financial support by the DFG via project SFB491-N1 is gratefully acknowledged.