Eur. Phys. J. B 8, 113-123 (1999)
https://doi.org/10.1007/s100510050673

Magnetic fluids in an external field

¹ Institute for Semiconductor Physics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria
² Institute for Theoretical Physics, University of Linz, Altenbergerstrasse 69, 4040 Linz, Austria

Received: 20 March 1998
Published online: 15 March 1999

Abstract

Within mean field approximation we investigate the phase diagrams of magnetic fluids in presence of a magnetic field. In a finite field the magnetic phase transition is absent, but instead a line of first order liquid-liquid transitions ending in a critical point occurs for a magnetic interaction, which is sufficiently strong. Varying the magnetic field these critical points extend from the tricritical point at H=0 to a critical endpoint. For a fluid with Ising spins we calculate the critical lines and several tricritical exponents analytically. For Heisenberg fluids we obtain the phase diagrams from a numerical solution of the mean field equations of state.