The phases of a magnetic fluid in an external field are considered. As model systems we take an ideal (hard core) gas with Ising interaction and a van der Waals gas with additional Heisenberg interaction. In mean field approximation various phases and critical points are identified. For appropriate values of the ratio of the magnetic to the non-magnetic interactions there exist multicritical points like tricritical points and critical end points. For the ideal Ising fluid we calculate the line of wing critical points analytically and prove classical tricritical behaviour. In the van der Waals case wing critical points and the gas-liquid critical point may coexist. The corresponding phase diagrams in (p, t, h) -space are shown.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.