Ordering effects of the dipolar interaction in lattices of small magnetic particles

The hysteresis curves of systems composed of small interacting magnetic particles, regularly placed on a two-dimensional lattice, are obtained with Monte Carlo simulations, for magnetic fields on the plane of the monolayer. The remanence as a function of temperature, in interacting systems, presents a peak that separates two different magnetic states. At low temperatures, small values of remanence are a consequence of antiferromagnetic order due to the dipolar interaction. At higher values of temperature the increase of the component normal to the lattice plane is responsible for the small values of remanence. The value of the temperature corresponding to the maximum value of remanence depends on lattice spacing and size. (C) 2004 Elsevier B.V. All rights reserved.