| Summary: | 碩士 === 國立彰化師範大學 === 物理學系 === 95 === In this study, we investigate the influence of geometrical asymmetry on magnetic reversal processes and magnetization transition of submicron struc-tured magnetic thin film. The circular magnetic dots are introducing a flat edge correlated with cut off a varying percentage of the round edge. The magnetic dots are fabricated as square array combining with electron beam lithography, electron gun evaporation and lift-off technique.
The magnetic properties are characterized by focused magneto-optical Kerr effect measurement in longitudinal geometry and micromagnetic numerical simulation. The hysteresis loops and magnetization configurations are obviously affected by shape asymmetry.
The magnetic switching behaviors can be control by introducing different size flat edges. The vortex nucleation fields shift backward the external field correlated to excised angel increasing. In addition, the vortex annihilation fields shift forward the applied field corresponding with excised angles increasing. In large excised angle case, it is found that the magnetic reversal mechanism is similar to a magnetic ellipse element.
In addition, in the small excised angle case, we have observed that the asymmetrical magnetic dots not only maintain the advantage of flux-closure magnetization, small stray field, but also can be used to control the vortex chirality.
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