Static polar Kerr hysteresis loops measured by slowly scanning magnetic field with and without pumping pulses, respectively. The amplitude of loops is normalized by the maximum Kerr rotation angle at saturation magnetization with no pumping. The chain line loop is obtained under a pump fluence of and at −5 ps pump-probe delay time.
(a) Dynamic Kerr hysteresis loops measured by the polar Kerr spectroscopy with a laser-synchronized SAMF for pump-on and pump-off pulses, respectively. Letters “a–d” denote magnetization states whose fs-laser-induced magnetization dynamics is measured in Fig. 3. (b) Normalized Kerr signal at and corresponding SAMF sampled synchronously vs delayed time between the SAMF and laser pulses. The curve of vs is just the chain line loop at −5 ps under a pump fluence of .
External field dependence of the ultrafast dynamics (solid lines) of fs-laser-assisted MO writing across measured by the polar Kerr spectroscopic setup with a laser-synchronized SAMF under the pump fluence of . Fittings are shown by the open circles. All Kerr signals are normalized by the saturation Kerr rotation angle without pumping.
Magnetization reversal rate vs the external field. The best linear fitting is shown by dashed line.
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