Crystallization of magnetic dipolar monolayers: a density functional approach

TL;DR

This paper uses density functional theory to analyze the crystallization process of super-paramagnetic particles in two dimensions under a magnetic field, emphasizing the importance of triplet correlations and non-perturbative methods for accurate predictions.

Contribution

It introduces a non-perturbative density functional approach that includes triplet correlations and allows for finite defect concentrations, improving agreement with experimental data.

Findings

Explicit triplet correlations are crucial for accurate predictions.

Non-perturbative methods outperform truncated Taylor expansions.

Allowing for finite defect concentrations enhances model realism.

Abstract

We employ density functional theory to study in detail the crystallization of super-paramagnetic particles in two dimensions under the influence of an external magnetic field that lies perpendicular to the confining plane. The field induces non-fluctuating magnetic dipoles on the particles, resulting into an interparticle interaction that scales as the inverse cube of the distance separating them. In line with previous findings for long-range interactions in three spatial dimensions, we find that explicit inclusion of liquid-state structural information on the {\it triplet} correlations is crucial to yield theoretical predictions that agree quantitatively with experiment. A non-perturbative treatment is superior to the oft-employed functional Taylor expansions, truncated at second or third order. We go beyond the usual Gaussian parametrization of the density site-orbitals by performing free minimizations with respect to both the shape and the normalization of the profiles, allowing for finite defect concentrations.