Magnetization reversal and vortex chirality correlation in ferromagnetic dot arrays

An overview of our research on vortex states in arrays of cobalt and permalloy dots is presented. At first a description of single-domain and vortex states is given together with a discussion of the dependence of magnetization reversal process on dot size and thickness. We then focus our attention on the vortex nucleation/annihilation process in arrays of closely spaced, interacting dots. Several phenomena are describet, including 1) a fourfold anisoptropy in a square array of circular Co dots, 2) formation of chains of vortices with identical chirality in a square array of Co dots, 3) formation of vortices with alternating chiralities in two-dot chains and in zig-zag chains as well as in a honeycomb array of permalloy dots. We show that a detailed investigation of the internal micromagnetic configurations of the dots by MFM imaging and micromagnetic simulations is necessary to understand these phenomena.