Monte Carlo simulations of interacting magnetic nanoparticles

Motivated by recent advances in synthesis techniques of nanometer size magnetic particles, we have performed Monte Carlo simulations of the magnetic properties of such assemblies of particles. The particles are assumed to be point dipoles, which interact magnetostatically and have uniaxial anisotropy. Spatial distributions of the particles are either generated numerically or are taken from experimental data sets. The properties, such as the remnant magnetization, are studied as a function of temperature for a wide range of parameters. The role of magnetostatic interaction is found to be important in many cases where it has typically been neglected. For example, we find that for a thin film of iron particles with 3.5 nm average diameter and only 13% area coverage, the magnetostatic interactions raise the blocking temperature by 20%, and the particles do not have Stoner-Wolfarth character.