Magnetic properties in monolayers of a model polydisperse ferrofluid -: art. no. 041105

The influence of polydispersity on the equilibrium properties of monolayers of three-dimensional dipolar spheres with short-range repulsive interactions is studied by means of Monte Carlo simulations and a high field approximation perturbation theory. The particle distribution in the simulations is realized in the semigrand ensemble by tuning appropriately the underlying particle distribution density. The magnetization curves are calculated as functions of density and temperature, and the obtained results are compared with the data determined in a monodisperse equivalent of the system. In-plane and out-of-plane initial magnetic susceptibilities are determined using external fields applied parallel or normal to the monolayer plane. Susceptibility data for the true two- and three-dimensional counterparts of the system are also calculated for comparison. Our findings for the magnetic properties can partly be explained by the structural characteristics obtained from the simulations.