Crystallization of magnetic dipolar monolayers: a density functional approach

Abstract

We employ density functional theory to study in detail the crystallization ofsuper-paramagnetic particles in two dimensions under the influence of an external magneticfield that lies perpendicular to the confining plane. The field induces non-fluctuatingmagnetic dipoles on the particles, resulting in an interparticle interaction that scales as theinverse cube of the distance separating them. In line with previous findings for long-rangeinteractions in three spatial dimensions, we find that explicit inclusion of liquid-statestructural information on the triplet correlations is crucial to yield theoreticalpredictions that agree quantitatively with experiment. A non-perturbative treatment issuperior to the oft-employed functional Taylor expansions, truncated at second orthird order. We go beyond the usual Gaussian parametrization of the densitysite-orbitals by performing free minimizations with respect to both the shapeand the normalization of the profiles, allowing for finite defect concentrations.