2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/27531We make for the first time a large-scale Monte-Carlo simulation of a ferromagnetic Heisenberg model with dipolar interactions on a two dimensional square lattice with open boundaries using an efficient new technique. We find that a phase transition occurs in the model and the ordered phase is characterized by a circular arrangement of the spins.8 pages, REVTex, 1 figure(Fig.1) availale upon request 5 figures(Fig.2-6) in ps-files uuencodedCondensed Mattertext