Orientational transitions in the magnetocompensated ferronematics with the homeotropic coupling of particles with matrix
DOI:
https://doi.org/10.17072/1994-3598-2017-1-31-40Abstract
In the framework of the continuum theory the orientational transitions induced by an external magnetic field in the ferronematic i.e. suspension of submicron particles of ferromagnetic material on the basis of a nematic liquid crystal were studied. The ferronematic was assumed to be compensated i.e., having equal fractions of ferroparticles with oppositely directed magnetic moments. In the absence of magnetic field that suspension is not magnetized and it is a liquid-crystalline analog of an antiferromagnetic. We took into account the following contributions of the free energy to the bulk density: the potential of elastic deformation of the director field, the interactions of diamagnetic matrix and magnetic moments of ferroparticles with the magnetic field, as well as contribution of the entropy of mixing of the ideal solution of suspension particles. Soft homeotropic coupling of ferroparticles with the molecules of the liquid crystal and soft planar coupling of the director with boundaries of the compensated ferronematic layer were considered. It was shown that in considered geometry the applying magnetic field leads to a redistribution of the magnetic impurity in the layer of ferronematic without appearance of orientational structure distortions. The initial antiferromagnetic ordering of the magnetic particles is replaced by a ferrimagnetic one with increasing of the fraction of particles oriented in the magnetic field direction. With increasing of magnetic field the uniform ferrimagnetic state becomes unstable and Freedericksz transition appears. The subsequent increasing of the magnetic field leads to transition to the uniform angular phase, in which the director and magnetization are oriented in the direction of the magnetic field and distortions of orientational structure have been disappeared. Expressions for the threshold transition fields between orientational phases of ferronematic as functions of material parameters were found analytically.Received 16.01.2017; accepted 10.05.2017References
de Gennes P. G. Physics of liquid crystals. Мoscow: Mir, 1977. 400 с.
Stewart I. W. The Static and Dynamic Continuum Theory of Liquid Crystals: A Mathematical Introduction. London: Taylor & Francis, 2004. 360 p.
Brochard F., Gennes de P. G. Theory of magnetic suspensions in liquid crystals. Journal de Physique, 1970, vol. 31, pp. 691–708.
Burylov S. V., Raikher Yu. L. Macroscopic properties of ferronematics caused by orientational interactions on the particle surfaces. II. Behavior of real ferronematics in external fields. Molecular Crystals and Liquid Crystals, 1995, vol. 258, pp. 123–141.
Kopčanský P., Tomašovičová N., Koneracká M., Závišová V., Timko M., Džarová A., Šprincová A., Éber N., Fodor-Csorba K., Tóth-Katona T., Vajda A., Jadzyn J. Structural changes in the 6CHBT liquid crystal doped with spherical, rodlike, and chainlike magnetic particles. Physical Review E, 2008, vol. 78, 011702.
Buluy O., Ouskova E., Reznikov Yu., Glushchenko A., West J., Reshetnyak V. Magnetically induced alignment of FNS. Journal of Magnetism and Magnetic Materials, 2002, vol. 252, pp. 159–161.
Zadorozhnii V. I., Reshetnyak V. Yu., Kleshchonok A. V., Sluckin T. J., Thomas K. S. Inverse Frederiks effect and bistability in ferronematic cells. Molecular Crystals and Liquid Crystals, 2007, vol. 475, pp. 221–231.
Zadorozhnii V. I., Sluckin T. J., Reshetnyak V. Yu., Thomas K. S. The Frederiks effect and related phenomena in ferronematic materials. SIAM Journal of Applied Mathematics, 2008, vol. 68, pp, 1688–1716.
Makarov D. V., Zakhlevnykh A. N. Tricritical phenomena at the Freedericksz transition in ferronematic liquid crystals. Physical Review E, 2010, vol. 81, 051710.
Podoliak N., Buchnev O., Buluy O., D'Alessandro G., Kaczmarek M., Reznikov Y., Sluckin T. J. Macroscopic optical effects in low concentration ferronematics. Soft Matter, 2011, vol. 7, pp. 4742–4749.
Mertelj A., Lisjak D., Drofenik M., Čopič M. Ferromagnetism in suspensions of magnetic platelets in liquid crystal. Nature, 2013, vol. 504, pp. 237–241.
Zakhlevnykh A. N., Petrov D. A. Weak coupling effects and re-entrant transitions in ferronematic liquid crystals. Journal of Molecular Liquids, 2014, vol. 198, pp. 223–233.
Zakhlevnykh A. N., Petrov D. A. Orientational bistability in ferronematic liquid crystals with negative diamagnetic anisotropy. Journal of Magnetism and Magnetic Materials, 2015, vol. 393, pp. 517–525.
Garbovskiy Yu. A., Glushchenko A. V. Liquid crystalline colloids of nanoparticles: preparation, properties, and applications. Solid State Physics, 2011, vol. 62, pp. 1–74.
Podoliak N, Buchnev O, Bavykin D. V., Kulak A. N., Kaczmarek M., Sluckin T. J. Magnetite nanorod thermotropic liquid crystal colloids: Synthesis, optics and theory. Journal of Colloid and Interface Science. 2012, vol. 386, pp. 158–166.
Tomašovičová N., Timko M., Mitróová Z., Koneracká M., Rajňak M., Éber N., Tóth-Katona T., Chaud X., Jadzyn J., Kopčanský P. Capacitance changes in ferronematic liquid crystals induced by low magnetic fields. Physical Review E, 2013, vol. 87, 014501.
Gdovinová V., Tomašovičová N., Éber N., Tóth-Katona T., Závišová V., Timko M., Kopčanský P. Influence of the anisometry of magnetic particles on the isotropic–nematic phase transition. Liquid Crystals, 2014, vol. 41, pp. 1773–1777.
Petrov D. A., Zakhlevnykh A. N. Freedericksz transition in compensated ferronematic liquid crystals. Molecular Crystals and Liquid Crystals. 2012, vol. 557, pp. 60–72.
Zakhlevnykh A. N., Petrov D. A. Influence of the segregation effect on the magnetic and optical properties of a compensated ferronematic liquid crystal. Technical Physics, 2012, vol. 57, pp. 1208–1218.
Zakhlevnykh A. N., Petrov D. A. Magnetic field induced orientational transitions in soft compensated ferronematics. Phase Transitions, 2014, vol. 87, pp. 1–18.
Zakhlevnykh A. N., Petrov D. A. Orientational bistability and magneto-optical response in compensated ferronematic liquid crystals. Journal of Magnetism and Magnetic Materials, 2016, vol. 401, pp. 188–195.
Zakhlevnykh A. N., Petrov D. A. Orientational Transitions in Antiferromagnetic Liquid Crystals. Physics of the Solid State, 2016, vol. 58, pp. 1906–1915.
Rapini A., Papoular M. Distorsion d'une lamelle nématique sous champ magnétique conditions d'ancrage aux parois. Journal de Physique Collo-que, 1969, vol. 30, pp. 54–56.
Blinov L. M., Chigrinov V. G. Electrooptic Effects in Liquid Crystal Materials. New-York: Springer-Verlag, 1994. 464 p.
Zakhlevnykh A. N. Threshold magnetic fields and Freedericksz transition in a ferronematic. Journal of Magnetism and Magnetic Materials. 2004, vol. 269, pp. 238–244.
Downloads
Published
How to Cite
Issue
Section
License
Автор предоставляет Издателю журнала (Пермский государственный национальный исследовательский университет) право на использование его статьи в составе журнала, а также на включение текста аннотации, полного текста статьи и информации об авторах в систему «Российский индекс научного цитирования» (РИНЦ).
Автор даёт своё согласие на обработку персональных данных.
Право использования журнала в целом в соответствии с п. 7 ст. 1260 ГК РФ принадлежит Издателю журнала и действует бессрочно на территории Российской Федерации и за её пределами.
Авторское вознаграждение за предоставление автором Издателю указанных выше прав не выплачивается.
Автор включённой в журнал статьи сохраняет исключительное право на неё независимо от права Издателя на использование журнала в целом.
Направление автором статьи в журнал означает его согласие на использование статьи Издателем на указанных выше условиях, на включение статьи в систему РИНЦ, и свидетельствует, что он осведомлён об условиях её использования. В качестве такого согласия рассматривается также направляемая в редакцию справка об авторе, в том числе по электронной почте.
Редакция размещает полный текст статьи на сайте Пермского государственного национального исследовательского университета: http://www.psu.ru и в системе OJS на сайте http://press.psu.ru
Плата за публикацию рукописей не взимается. Гонорар за публикации не выплачивается. Авторский экземпляр высылается автору по указанному им адресу.
