Hysteresis curve of magnetic nanocrystals monolayers: Influence of the structure

We calculate the magnetization curve at vanishing temperature of a monolayer of spherical single domain magnetic nanocrystals in terms of the structure of the monolayer. The magnetization curve of a square lattice of particles is compared to those of disordered monolayers. The particles on the disordered monolayers are either distributed isotropically on the surface or organized in chains, which are either linear and or totally flexible. A strong effect of the structure is found only in the case of linear chains and when the magnetization is measured along the chains direction. In the experimental part a monolayer of cobalt nanoparticles organized in a chainlike structure is elaborated by applying a magnetic field during the evaporation of a ferrofluid on a substrate. The change of the magnetization curve due to the chainlike structure is compared to that of the model. (C) 2003 American Institute of Physics.