Figure 4. Time-resolved all-optical magnetic switching as observed by femtosecond single-shot imaging.
Time-dependence of the normalized magnetization projection on the [001] axis MZ with respect to the saturation magnetization. The data points were calculated as the ratio of the magneto-optical signal (the average image contrast) in the switched area to the magneto-optical signal in the case when the magnetization is aligned along the [001] axis. The red solid line was fitted using the exponential increase (1−exp[−Δt/τ]) with the characteristic time τ=19.5±1.6 ps. The top panel shows the images of domains obtained at different time-delays after subtraction of the reference image obtained at negative Δt. The inset shows the schematics of the magnetization trajectory during the switching. The magnetization is switched between M(L)+ and M(L)−states with the help of the laser pulse polarized along the [100] axis. The pump fluence was 150 mJ cm-2 and the central wavelength of the pump was 1250 nm. The size of the images is 240×210 μm2.