title: Competition between local disordering and global ordering fields in nematic liquid crystals.
abstract: We study the influence of external electric or magnetic field B on orientational ordering of nematic liquid crystals or of other rod-like objects (e.g. nanotubes immersed in a liquid) in the presence of random anisotropy field type of disorder. The Lebwohl-Lasher lattice type of semi-microscopic approach is used at zero temperature. Therefore, results are valid well below the transition into the isotropic phase. We calculate the correlation function of systems as a function of B, concentration p of impurities imposing random anisotropy field disorder, the disorder strength W and system dimensionality (2D and 3D systems). In order to probe memory effects we calculate correlation length ξ for random and homogeneous initial configurations. We determine the crossover fields B(c)(p) separating roughly the ordered and disordered regime. Memory effects are apparent only in the latter case, i.e. for B < B(c).PACS numbers: 47.51.+a, 47.54.-r, 07.05.Tp, 61.30.-v.
authors.affiliation: Regional Development Agency Mura Ltd, Lendavska 5a, 9000 Murska Sobota, Slovenia, Laboratory of Physics of Complex Systems, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška 160, 2000 Maribor, Slovenia. Matej.Cvetko@rra-mura.si
authors.forename: Matej
authors.initials: M
authors.lastname: Cvetko
authors.forename: Milan
authors.initials: M
authors.lastname: Ambrozic
authors.forename: Samo
authors.initials: S
authors.lastname: Kralj