Phase Diagram of the mixed spin-2 and spin-5/2 Ising system with two   different single-ion anisotropies
  In this paper we present a study of the effects of two different single-ion anisotropies in the phase diagram and in the compensation temperature of the mixed spin-2 and spin-5/2 Ising ferrimagnetic system. We employed the mean-field theory based on the Bogoliubov inequality for the Gibbs free energy. Also we found the Landau expansion of the free energy in the order parameter to describe the phase diagrams. In the plane critical temperature versus single-ion anisotropie the phase diagram displays tricritical behavior. The critical and compensation temperatures increase when the single-ion anisotropies increase. 
J. S. da Cruz Filho, M. Godoy and A. S. de Arruda
cond-mat.stat-mech