Discontinuous orientational changes in nematics effects of electric and magnetic fields

Kini, U.D.

Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/2920

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DC Field	Value	Language
dc.contributor.author	Kini, U.D.	-
dc.date.accessioned	2007-06-18T04:43:23Z	-
dc.date.available	2007-06-18T04:43:23Z	-
dc.date.issued	1990-12	-
dc.identifier.citation	Liquid Crystals, 1990, Vol.8, p745 - 763	en
dc.identifier.issn	0267-8292	-
dc.identifier.issn	1366-5855 (online)	-
dc.identifier.uri	http://hdl.handle.net/2289/2920	-
dc.description	Restricted Access.	en
dc.description.abstract	Theoretical studies are presented on discontinuous changes produced in homogeneous deformations under the competing influences of an electric field E applied parallel to the sample planes and a magnetic field H applied at different angles in the plane containing E and n0 the initial director orientation. Orientational bistability can be affected by the tilt of n0 at the boundaries, the relative magnitudes of H and E, the tilt angle of H and even the order in which E and H are applied to the sample. In particular, the bend transition can be made continuous by applying H parallel to E in materials with positive diamagnetic susceptibility anisotropy (Xa > 0). Depending upon the tilt of H and the relative strengths of H and E it may be possible to change (continuously or otherwise) the nature of distortion in domains. Ab initio calculations show that the E induced twist transition should be continuous in samples having lateral dimensions large compared with thickness. In such a sample one can envisage the possibility of removing the discontinuity at the Freedericksz transition by tilting n0 sufficiently away from the homeotropic in a plane normal to E. A more complete theoretical analysis may be necessary to understand the discontinuous twist Freedericksz transition observed experimentally when the electrode gap is not large compared to the sample thickness. The possibility that the hysteresis width of a discontinuous Freedericksz transition might depend on domain formation above threshold cannot be ruled out. In the bend geometry non-rigid anchoring of the director at the boundaries is briefly dealt with to indicate that flexoelectricity might play a role in the initial build up of low level deformation prior to the transition when E is static. The flexoelectric contribution may become negligible in the presence of a sufficiently strong stabilizing H when the anchoring is strong enough and E is time varying. On the basis of the present results and previous work it may be concluded that variation of tilt of H may have considerable influence on the formation of the modulated phase above the bend transition.	en
dc.format.extent	1298151 bytes	-
dc.format.mimetype	application/pdf	-
dc.language.iso	en	en
dc.publisher	Taylor & Francis	en
dc.relation.uri	http://dx.doi.org/10.1080/02678299008047386	en
dc.rights	1990 Taylor & Francis	en
dc.title	Discontinuous orientational changes in nematics effects of electric and magnetic fields	en
dc.type	Article	en
Appears in Collections:	Research Papers (SCM)

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