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Experimental results of magnetic vortex core polarity reversal. The initial core polarity was up, determined from the sense of the vortex gyration revealed by the TR-PEEM images taken with 1 mT field pulses [panel (a)]. The core polarity was reversed to down polarization after pulsing at 5 mT for 2 s for the second time [panel (b)]. The core polarity was switched back to up polarization after the fourth pulse train.
Transient domain states observed both in experiment and simulation shortly after the falling edge of a 5 mT excitation pulse (removed at time ). The experimental PEEM images (top row) agree well with the micromagnetic simulations (second row). The cross-sectional plots of along the direction (bottom row) reveal that the vortex core is replaced by a complex cross-tie domain wall consisting of a series of cores of both positive and negative polarities.
Simulated domain wall evolution in a disk. Sequence shows the detailed evolution of the central domain wall region for the first 6.6 ns. This simulation is for a -diameter disk excited by a 5 MT pulse amplitude with 200 ps fall time and other simulation parameters are the same as described in the manuscript. The movie is zoomed into a area centered along the direction, shifted up by in the direction. The red and blue represent the magnitude of the magnetic moment along + and , respectively. (Enhanced online.) [URL: http://dx.doi.org/10.1063/1.3111430.1]10.1063/1.3111430.1
Micromagnetic simulations of core reversal probability for a 500-nm-diameter, 30-nm-thick disk at using ten different random seeds. The top panel shows whether the core polarity changed (yellow/light) or stayed the same (blue/dark) on the rising and falling edges of the pulse. White indicates an undetermined (multivortex or expelled vortex) state. The lower panel summarizes the overall probability of core reversal as a function of the field pulse amplitude excluding undetermined states.
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