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MA: Magnetismus

MA 6: Hauptvortr
äge Stoll / Fiebig

MA 6.1: Hauptvortrag

Freitag, 4. März 2005, 14:00–14:30, TU H1028

Sub-ns Time-Resolved Magnetic Transmission X-Ray Microscopy — •Hermann Stoll — Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart

Fast magnetization dynamics of ferromagnetic elements on short length scales is currently attracting substantial scientific interests for both technological and fundamental reasons [1]. Experiments with a time resolution of 70-100 ps combined with a lateral resolution of 20-40 nm were performed by implementing stroboscopic ‘pump-and-probe’ techniques into a full-field soft X-ray microscope (XM-1, beamline 6.1.2, ALS, Berkeley) [2] and a scanning transmission X-ray microscope (STXM, beamline 11.0.2, ALS). The scanning microscope equipped with a fast avalanche photo diode (APD) detector allowed us to speed up time-dependent measurements on micron-sized patterns by about a factor of 10. Spin precession [2] and gyrotropic vortex motion in micron-sized ferromagnetic patterns were studied. Complementary to the time-domain ‘pump-and-probe’ measurements we developed a frequency-domain ‘spatially-resolved ferromagnetic resonance (SR-FMR)’ technique in order to excite specific eigenmodes of ferromagnetic patterns. A novel effect has been found: the sense of the gyrotropic vortex motion in micron-sized Permalloy patterns may be changed by adjusting the excitation power in a SR-FMR experiment. This allows a deliberate and reproducible switching of the vortex core chirality (handedness).
[1] I. Tudosa et al., Nature 428 (2004) 831
[2] H. Stoll et al., Appl. Phys. Lett. 84 (2004) 3328