Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.367, 2963-2970, 2001
One-dimensional structures in ferrocholesteric film with weak homeotropic anchoring on the layer boundaries
We consider one-dimensional structures of a ferrocholesteric film with weak anchoring of homeotropic type on the boundaries of the layer. We assume that the external magnetic field is oriented normal to the plane of the layer and diamagnetic anisotropy of cholesteric liquid crystal matrix is positive. We rind that two kinds of ordering can exist in the layer with weak homeotropic anchoring on its boundaries: ferronematic (FN) and ferrocholesteric (FC) states. It is shown that variation of the surface anchoring strength between the cholesteric molecules and layer boundaries can induce the FN-FC transition, and can lead to a change of the phase transition character from the first order to second order one. The critical parameters of the transition between FC and FN states are determined as a function of FC material parameters. At present study of orientational and magnetic properties of FN-FC transition the so-called segregation effect are taken into account: the concentration redistribution of the magnetic admixture under the influence of a magnetic field.