Ultrafast magnetization reversal dynamics investigated by time domain imaging

Spatiotemporal magnetization reversal dynamics in a Ni80Fe20 microstructure is studied using ps time scale scanning Kerr microscopy. Time domain image s reveal a striking change in the reversal associated with the reduction in switching time when a transverse bias field is applied. Magnetization osci llations subsequent to reversal are observed at two resonance frequencies, which sensitively depend on the bias field strength. The oscillation at f = 2 GHz is caused by the damped precession of M, while the lower frequency s imilar to0.8 GHz mode is interpreted in terms of domain wall oscillation. D OI: 10.1103/PhysRevLett.86.728.