FERRIMAGNETIC PHASES IN THE BLUME-EMERY-GRIFFITHS MODEL - IMPLICATIONS FOR THE ANTIFERROMAGNETIC POTTS-MODEL

The cluster-variation method is used to study the phase diagram of the Blume-Emery-Griffiths model on a simple cubic lattice. The main atten tion is paid to the ferrimagnetic phases occurring in a certain range of coupling parameters. A new topology, including three ferrimagnetic phases, is obtained in the vicinity of the line in parameter space whe re the model reduces to the antiferromagnetic three-state Potts model. The results imply the existence of three phase transitions in the ant iferromagnetic Potts model.