Statistical thermodynamics of ferronematic

In this paper we investigate theoretically the equilibrium phase transitions in ferronematics taking into account the steric and magnetic interactions of colloid particles. The systems of two kinds are considered: in the first one the particles magnetic moment can be parallel or antiparallel to the director of nematics and in the second one it can only be parallel. Phase diagrams of separation of a system on the regions with high and low concentration of the particles in the external magnetic field are constructed. The external magnentic field is shown to stimulate this separation. It has been found that magnetic interaction of particles decreases the critical field of Fredericks effect and increases the deformation amplitude of structure of the system in this phenomenon. The existence of domain structures in thin gaps filled by ferronematics of the second kind is predicted.