Interaction effects in a two-dimensional array of ferromagnetic dots

The magnetostatic interaction effects in small clusters of magnetically soft ferromagnetic dots are studied by means of numerical simulation. The thickness of the particles is given by 20 divided by 40 nm, the diameters are within the range of 200 divided by 400 nm, saturation magnetization M-s = 800 divided by 1000 G, exchange constant C = 2.10(-6) erg/cm. The hysteresis loop of two interacting dots being in magnetization curling states is investigated as function of distance between particle centers. Analytical approximation is suggested for the two-paticle interaction effect. Also, limiting case of single domain cylindrical dots arranged in square lattice is considered. Hysteresis loops of such dot array depend on in-plane magnetic field direction and reveal the fourfold anisotropy. Some experimental results obtained for the submicron dot arrays are discussed.