How to Enhance Sensitivity of Liquid Crystals to External Magnetic Field?

P. Kopčanskýa, N. Tomašovičová a, V. Gdovinová a, M. Timko a, N. Éber b, T. Tóth-Katona b, J. Jadzyn c, J. Honkonen d and X. Chaud e aInstitute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Kosice, Slovakia bInstitute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 49, Hungary cInstitute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60179 Poznan, Poland dDepartment of Physical Sciences, University of Helsinki, Gustav Hällstromin katu 2, Helsinki, Finland eHigh Magnetic Field Laboratory, CNRS, 25 Avenue des Martyrs, Grenoble, France

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Liquid crystals, due to their large dielectric anisotropy, respond very sensitively to application of an external electric field, whereas they are only weakly sensitive to the magnetic field. A possible way of improving that sensitivity is doping liquid crystals with magnetic nanoparticles. As a result, stable colloidal suspensions of liquid crystals with relatively low concentrations of magnetic nanoparticles (called ferronematics, ferrocholesterics, ferrosmectics, etc.) can be produced. We illustrate some examples of the influence of the magnetic field, as well as of a superposition of magnetic and electric fields on the structural transitions (e.g. on the Fréedericksz transition) in ferronematics based on the calamitic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT). It is shown that the samples respond to the applied magnetic field of low strength. The effects of the magnetic particles and magnetic field on the nematic to isotropic phase transition temperature are discussed as well.

DOI: 10.12693/APhysPolA.127.157 PACS numbers: 75.50.Mm, 61.30.Gd, 61.30.Hn