The sensitivity of ferronematics to external magnetic fields

The stable colloidal suspensions of nematic liquid crystals with magnetic nanoparticles are called ferronematics. Their behaviour in magnetic field depends on an anchoring energy, volume concentrations of magnetic nanoparticles and sign of anisotropy of diamagnetic susceptibility of liquid crystal as well as on the initial orientation between director (n) of liquid crystal and magnetic moment (m) of magnetic nanoparticles. In this work we present structural changes in ferronematics based on two kinds of liquid crystals: 6CHBT (positive anisotropy of diamagnetic susceptibility) and ZLI1695 (negative anisotropy of diamagnetic susceptibility) exposed to high magnetic fields. In both cases the parallel initial orientation between director and magnetic moments is fulfilled. The density of anchoring energy between liquid crystal molecules and magnetic particles was determinated by Burylov and Raikher's theory. In the case of 6CHBT-based ferronematics the decrease while in the case of ZLI1695-based ferronematics the increase of the critical magnetic field were observed.