Anisotropic magnetic coupling of permalloy micron dots forming a square lattice

Static magnetic and spin wave properties of square lattices of permalloy micron dots with thicknesses of 500 and 1000 Angstrom and with varying dot separations have been investigated. A magnetic fourfold anisotropy was found for the lattice with dot diameters of 1 mu m and a dot separation of 0.1 mu m. The anisotropy is attributed to an anisotropic dipole-dipole interaction between magnetically unsaturated parts of the dots. The anisotropy strength (order of 10(5) erg/cm(3)) decreases with increasing in-plane applied magnetic field. (C) 1997 American Institute of Physics.