Binary mixtures of magnetic fluids

We study a binary mixture of a van der Waals fluid and a ferromagnetic fluid at zero magnetic field on the basis of the mean field Ising fluid model and the van der Waals theory with quadratic mixing rules. Depending on three reduced parameters, the phase diagram shows a surface of magnetic phase transitions and lines of tricritical points, critical end points, and magnetic consolute points. First-order phase transition surfaces and critical lines are calculated numerically. For the line of tricritical points, which can occur in two different topologies, an analytic expression is derived. All higher-order lines and coexistence surfaces are visualized in three-dimensional x, T, p and xi, T, p diagrams, where xi is a mapping of delta, the conjugated field of the mole fraction x, on the unit interval.