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Experimental setup for time-resolved magneto-optical Kerr microscopy. P1, P2: polarizer, F: band pass filter, QWP1, QWP2: quarter wave plate, HWP: half wave plate, VL: vibrating lens. Inset shows that schematic drawing of experimental sequence. The magnetization is initialized by heating with the laser diode illumination under a magnetic field before each pump irradiation.
(a) Temporal evolution of magnetization reversal induced by femtosecond photoirradiation. An external magnetic field of 170 Oe was applied antiparallel to the initial magnetization direction. The pump spot size was FWHM. The pump pulse energy was 320 pJ . The lower right image shows the spatial profile of the pump spot. (b) Temporal profiles at A: , B: , and C: , where is distance from the center of the pump spot. (c) Schematic illustration of the magnetization dynamics. Dipole-dipole interaction enhances the effective magnetic field.
Change in magnetic domain structure on femtosecond optical pulse irradiation on the domain wall without external field. A circular magnetic domain is prepared prior to photoirradiation (−10 ps). A femtosecond optical pulse with pulse energy of and the spot size of FWHM is irradiated on the domain wall (10 ps). Staggered magnetic domains appear due to dipole-dipole interaction with each domain (10 ns).
(a) Pump pulse energy dependence of temporal evolution. An external magnetic field of 170 Oe was applied antiparallel to the initial magnetization direction. The pump spot size was FWHM. The bar denote . (b) Pump pulse energy dependence of the temporal profiles near the edge in reversed area. The is the time constant of magnetization reversal.
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