Orientational transitions in antiferromagnetic liquid crystals

The orientational phases in an antiferromagnetic liquid crystal (ferronematic) based on the nematic liquid crystal with the negative anisotropy of diamagnetic susceptibility are studied in the framework of the continuum theory. The ferronematic was assumed to be compensated; i.e., in zero field, imp...

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Bibliographic Details
Published in:Physics of the solid state 2016-09, Vol.58 (9), p.1906-1915
Main Authors: Zakhlevnykh, A. N., Petrov, D. A.
Format: Article
Language:English
Subjects:
Anchoring
Anisotropy
Antiferromagnetism
Bifurcations
Bistability
Crystal structure
Crystals
Diamagnetism
Ferrimagnetism
Freedericksz transitions
Impurities
Liquid Crystals
Magnetic fields
Magnetic moments
Magnetic permeability
Magnetic properties
Magnetism
Mathematical analysis
Nematic crystals
Parameters
Phase transitions
Physics
Physics and Astronomy
Saturation
Solid State Physics
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Summary:The orientational phases in an antiferromagnetic liquid crystal (ferronematic) based on the nematic liquid crystal with the negative anisotropy of diamagnetic susceptibility are studied in the framework of the continuum theory. The ferronematic was assumed to be compensated; i.e., in zero field, impurity ferroparticles with the magnetic moments directed parallel and antiparallel to the director are equiprobably distributed in it. It is established that under the action of a magnetic field the ferronematic undergoes orientational transitions compensated (antiferromagnetic) phase–non-uniform phase–saturation (ferrimagnetic) phase. The analytical expressions for threshold fields of the transitions as functions of material parameters are obtained. It is shown that with increasing magnetic impurity segregation parameter, the threshold fields of the transitions significantly decrease. The bifurcation diagram of the ferronematic orientational phases is built in terms of the energy of anchoring of magnetic particles with the liquid-crystal matrix and magnetic field. It is established that the Freedericksz transition is the second-order phase transition, while the transition to the saturation state can be second- or first-order. In the latter case, the suspension exhibits orientational bistability. The orientational and magnetooptical properties of the ferronematic in different applied magnetic fields are studied.
ISSN:1063-7834
1090-6460
DOI:10.1134/S1063783416090341