Lattice Models for Magnetic Fluids: Correlations Between Order Parameters

Magnetic fluids are colloidal suspensions of ferromagnetic particles covered with a surfactant layer, dispersed in a host liquid. The existence of cooperative phenomena in such magnetic colloidal systems, makes the determining of their physical properties a difficult task. In the framework of statistical mechanics, taking into consideration interparticle interactions, the study of equilibrium properties and phase transitions of magnetic fluids can be best done. In this paper we analyze some basic aspects about the real possibility of describing the critical properties of these systems in the language of spin-1 lattice-gas model and we also propose the use of a higher spin (3/2) model.