Magneto-Optical Response of Twisted Ferronematic Cells

We construct a theoretical model for a thermotropic ferronematic (magnetic liquid crystal colloid) in an asymmetric twisted nematic cell, subject to in-plane magnetic fields. At low colloidal concentrations, the nematic director [ncirc] is unchanged by strong fields, the magnetic director [mcirc] principally responds to its coupling to [ncirc], and the suspension density peaks sharply where [mcirc] and H are co-aligned. At higher concentrations feedback between [mcirc] and [ncirc] aligns [ncirc] over a significant part of the cell, and the suspension divides into a region where [ncirc] is parallel to H , and a region where it is not. We also make calculations of the optical properties of this cell.