| Summary: | 碩士 === 國立彰化師範大學 === 物理學系 === 96 === The magnetization configurations on the large area of nanometer-sized permalloy(Ni80Fe20) dots array and their reversal processes have been studied through magnetic force microscopy, alternate gradient magnetometer, magnetoresistance measurements, and micro-magnetism simulations, respectively. A standard electron beam lithography in combination with a lift-off process was used for patterning 30nm thick of millions of permalloy dots array with diameters of 250, 500, 750nm and the aspect ratio S/D of spacing to diameter ranging from 0.2 to 1.8, in which the highest density is up to 3Gb/in2 . The hysteresis loops through a nucleation and annihilation of vortex were observed all over the studied dots array by using an alternate gradient magnetometer. The results were further confirmed utilizing magnetic force microscopy in the presence of external magnetic field. The vortex nucleation and annihilation fields increase with decreasing diameter and increasing spacing. For smaller S/D dots array the vortex has a sharp displacement, whereas the larger S/D dots array reveals an extra slow vortex displacement before returning back to remanence from saturation. These facts are believed to be associated with the interdot interaction in the dots array. The unusual behavior was confirmed in the corresponding micro-magnetism simulations.
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