Tricritical phenomena at the Fréedericksz transition in ferronematic liquid crystals

Abstract

Within the continuum theory we study the magnetic segregation effects in ferronematics, i.e., suspensions of monodomain magnetic particles in nematic liquid crystals. Orientational and concentrational distributions in a ferronematic layer are obtained as functions of a magnetic field strength for different values of material parameters. Tricritical behavior of the Fréedericksz transition in ferronematics induced by magnetic field is revealed. It is found out that this transition can be either first- or second-order transition depending on the segregation degree. We derive the analytical expression for the tricritical segregation parameter, determining the phase-transition character change. The dependence of birefringence on the external magnetic field and the segregation parameter is studied.

Macroscopic optical effects in low concentration ferronematics

“…The coupling between the ferroparticle and the liquid crystal molecule orientations then transfers the magnetic orientational effect onto the underlying liquid crystal matrix. Ferronematics have attracted considerable interest [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] over the years because, in principle, they should exhibit higher magnetic susceptibilities than undoped liquid crystals, resulting in evident device applications.…”

Effects of surface anchoring on the electric Frederiks transition in ferronematic systems

“…In addition, to solve the differential equation (8), we use the finite difference method together with the relaxation method and Maxwell construction which are described in the following sections. To our knowledge, several physical approximations have been applied to solve the total 6 free energy in previous works [9,10,24,11,27,29,30]. The electric field in the free energy potential (7) and in the governing Eq.…”

Orientational bistability in ferronematic liquid crystals with negative diamagnetic anisotropy

“…[31,33] for the estimation of non-dimensional parameters (in CGS units) 7 10 | |  a  , 7 1 10  K dyne, 5 10  f , 2 4 10 10     w dyne cm 1 , 2 10 s M Gs, 6 10  d cm, 5 .…”