The molecular-field description of the isotropic-nematic phase transition in liquid crystals is investigated. It is found that the effects of fluctuations may be observable, and the first corrections due to fluctuations to the light scattering and magnetic birefringence in the isotropic phase are determined. The effects of applied fields on the phase transition are investigated. It is found that if the molecules prefer to line up transverse to an applied field there is a critical field above which the phase transition is second order.

• Received 7 July 1970

DOI:https://doi.org/10.1103/PhysRevLett.25.500