Ultrafast magnetization reversal dynamics in a ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ microstructure (10 μm by 2 μm in size and 15 nm thick) is studied using time-resolved scanning Kerr microscopy. The temporal evolution of the magnetization reversal reveals a dramatic reduction in switching time, when a steady transverse biasing field accompanies the pulsed longitudinal switching field applied to the sample. According to the analysis of time-domain images, it is concluded that the abrupt change of the switching time is due to a change in the magnetization reversal mode: the nucleation dominant reversal process is replaced by quasicoherent domain wall motion in the presence of an additional transverse biasing field. The experimental data are compared to results from micromagnetic modeling, based on the Landau-Liftshitz-Gilbert equation. The observed distinct magnetization reversal behaviors dependent on applied field conditions are well reproduced in the simulations.

• Received 12 April 2001

DOI:https://doi.org/10.1103/PhysRevB.64.144418