Effect of an external magnetic field on the gas-liquid transition in the Ising spin fluid

The theoretical phase diagrams of a magnetic (Ising) lattice fluid in an external magnetic field are presented. It is shown that, depending on the strength of the nonmagnetic interaction between particles, various effects of the external field on the Ising fluid take place. In particular, at moderate values of the nonmagnetic attraction the field effect on the gas-liquid critical temperature is nonmonotonic. A justification of such behavior is given. If short-range correlations are taken into account (within a cluster approach), the Curie temperature also depends on the nonmagnetic interaction strength.