QUASI-STATIC REMAGNETIZATION PROCESSES IN 2-DIMENSIONAL SYSTEMS WITH RANDOM ON-SITE ANISOTROPY AND DIPOLAR INTERACTION - NUMERICAL SIMULATIONS

We have developed a method that enables a fast and exact evaluation of the long-range interaction field by simulating the lattice dipolar sy stems with periodic boundary conditions. The method is based on the co mbination of the fast-Fourier-transformation technique and the modifie d Ewald method for the lattice sum calculation. We have used our algor ithm for simulations of the quasistatic remagnetization processes in t wo-dimensional hexagonal lattices of dipoles with the uniaxial on-site anisotropy (anisotropic Heisenberg model with the long-range dipolar interaction), which can be considered as a plausible model of a thin p olycrystalline magnetic film with the intergrain exchange and with eac h crystallite having its own single-grain anisotropy. During the remag netization process we observe typical ripplelike magnetization structu res well known from the experimental observations. The parameters of t hese structures as functions of the exchange and anisotropy strength a re studied.