Structural phase transition of a nematic liquid crystal doped with magnetic nanoparticles, under electric, magnetic and optical fields

Nematic liquid crystals doped with magnetic nanoparticles, called ferronematics, are among the new colloidal suspensions with critical magnetic properties. Dispersing magnetic nanoparticles in a cholesteric liquid crystal medium also leads to the creation of the other phase of anisotropic magnetic fluids known as ferrrocholesteric. In fact, the ordering behavior and some features of these new materials are drastically influenced by the presence of magnetic nanodopants. The transition field and orientational ordering depend on the volume fraction and magnetic moment of the dispersed particles as well as the external and material parameters such as magnetic anisotriopy and the cell thickness of a liquid crystal cell. The investigation of these new anisotropic nanomaterials is very important not only from the theoretical point of views but also practical application in nanotechnology. In this work we consider a ferrocholesteric cell with homeotropic anchoring conditions on the cell walls and soft anchoring modes on the ferrpparticle surfaces. Then, we study the stability of the system and transition to a feronematic state caused by exposure to a laser beam and under applied magnetic and electric fields.