Schematic illustrations of (a) one-side-flat disk with excised angle θ, adopted to represent the degree of asymmetry. Scanning electron microscopy (SEM) images of 800 nm Py disk for: (b) low asymmetry case with 30° excised angle; and (c) high asymmetry case with 75° excised angle, respectively.
Schematic illustrations of magnetic moments in disk with eminent asymmetry at: (a) longitudinal positive/negative saturation state, (b) remanent state in CW/CCW configuration, (c) a small right direction external field, and (d) annihilation field of CCW vortex.
Full hysteresis loop of low asymmetry Py (30° excised angle) disk array with (a) reverse loops returned at external fields of 150, 100, 0 and −100 Oe, and (b) reverse loops returned at external fields of −300, −400, −500, and −600 Oe. The insets schematically represent the vortex types in different loops at remanent state.
Full hysteresis loop of high asymmetry Py (75° excised angle) disk array with (a) reverse loops returned at external field of 0, −25, −50, −100, and −200 Oe, and (b) reverse loops returned at external field of −450, −500, −600, and −700 Oe. The insets schematically represent the vortex types in different loops at remanent state.
(a) Numerical simulated hysteresis loop for Py disk with diameter of 800 nm, thickness of 30 nm, and excised angle of 75°. The full loop is calculated with external field from +5000 to −5000 Oe and back to +5000 Oe. The −150 Oe loop is from +5000 to −150 Oe and back to +5000 Oe. For easy comparison with Fig. 3 , the hysteresis loops only show the range from +800 to −800 Oe. (b) Simulated magnetization distributions of the disk in full and reverse loops during ascending branch at external field of: (i) +125 Oe, (ii) +260 Oe, (iii) +300 Oe, (iv) +500 Oe, and (v) +575 Oe, respectively.
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