Phase Behaviour of Nematics in the Presence of Electric and Magnetic Fields

Abstract

We employ mean field theory to study the phase behaviour of nematics in the presence of arbitrary electric and magnetic fields. A rotationally invariant pseudopotential is used. If the molecules have cylindrical symmetry, the most general situation is equivalent to perpendicular electric and magnetic fields. The numerical calculations are carried out within the Maier-Saupe model, but it is demonstrated how the formalism can be extended to a generalized van der Waals theory in which pressure dependence can also be studied. We consider the cases where the electric and magnetic susceptibility anisotropies are both positive, negative and of opposite sign. Relationships between the responses in these situations are found and predictions are made regarding the field dependence of the order parameters and the transition temperatures.