Theoretical model for layer reorientation in smectic A* liquid crystals subject to an oblique magnetic field

Abstract

Recently, Carlsson and Osipov reported on observations of the rotation of smectic layers under certain experimental conditions, and a dynamic theory describing such rotations was presented [Carlsson, T., and Osipov, M. A., 1999, Phys. Rev. E, 60, 5619]. In the present work, the rotational motion of the smectic layers of a SmA* liquid crystal, over which an oblique magnetic field has been applied, is studied theoretically by the aid of this theory. The role of the interaction between the smectic layers and the substrates is discussed and it is shown that if this interaction is small enough, the smectic layers orient themselves in such a way that the layer normal is almost parallel to the magnetic field. The relevant material parameters governing the dynamical response of the induced tilt and the layer normal are identified, and the time dependence of the response of these two dynamical variables is calculated. From this calculation, expressions for the response times of the system are given and a numerical value of the rotational viscosity of the smectic layers is estimated.