Abstract
Magnetostatic interactions in different polycrystalline permalloy dot patterns for dots with diameter 900nm and thickness 30nm are investigated through magnetic force microscopy imaging, magneto-optic Kerr effect measurements, and micromagnetic simulations. Magnetization reversal occurs through vortex nucleation∕annihilation. Vortex nucleation and annihilation fields for different interacting arrays were observed to vary with pattern type and with the applied field direction and were shown to follow the prediction of a simple point-dipole model. The vortex chirality was established by imaging vortices in a small applied field. The vortex chirality distribution was determined for different arrays and a well-defined ordering phenomenon of the vortex chirality was observed in two-dot and zigzag-dot chain patterns as well as in a honeycomb array of dots. Micromagnetic simulations well account for the type of vortex chirality ordering observed and attribute it to magnetostatic interactions that induce correlated C-state magnetization configurations among nearest neighbor dots prior to vortex nucleation.
Published Version
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