Peculiarities in the Director Reorientation and the NMR Spectra Evolution in a Nematic Liquid Crystals under the Effect of Crossed Electric and Magnetic Fields

The illustrative description of the field-induced peculiarities of the director reorientation in the microsized nematic volumes under the effect of crossed magnetic B and electric E fields have been proposed. The most interesting feature of such configuration is that the nematic phase becomes unstable after applying the strong E. The theoretical analysis of the reorientational dynamics of the director field provides an evidence for the appearance of the spatially periodic patterns in response to applied large E directed at an angle a to B. The feature of this approach is that the periodic distortions arise spontaneously from a homogeneously aligned nematic sample that ultimately induces a faster response than in the uniform mode. The nonuniform rotational modes involve additional internal elastic distortions of the conservative nematic system and, as a result, these deformations decrease of the viscous contribution Uvis to the total energy U of the nematic phase. In turn, that decreasing of Uvis leads to decrease of the effective rotational viscosity coefficient g eff (a). That is, a lower value of g eff (a), which is less than one in the bulk nematic phase, gives the less relaxation time t on (a) g eff (a), when a is bigger than the threshold value a th. The results obtained by Deuterium NMR spectroscopy confirm theoretically obtained dependencies of t on (a) on alpha.