ࡱ> 6855@0Jbjbj22."XXJ LLLL,x:" $6R%===%:=B= ;; L^;$P0;P(P;P;: l%%$DINVERSE FREDERIKS EFFECT IN FERONEMATIC CELLS N. P. Podoliak, V. I. Zadorozhnii, V. Yu. Reshetnyak Physics Faculty, Kyiv National Taras Shevchenko University, Prospekt Glushkova 2, Building 1, Kyiv, Ukraine,  HYPERLINK "mailto:NinaPodol@gmail.com" NinaPodol@gmail.com,  HYPERLINK "mailto:viza@mail.univ.kiev.ua" viza@mail.univ.kiev.ua,  HYPERLINK "mailto:VReshetnyak@univ.kiev.ua" VReshetnyak@univ.kiev.ua ABSTRACT Ferronematic (FN) is a colloid of magnetic monodomain particles in a nematic liquid crystal host. An essential feature of FN is the macroscopic collective behavior - a long-range uniform orientational distortion of the FN matrix above some critical concentration of the solid phase. Therefore magnetic susceptibility of the FN system is considerably enhanced compared to the pure liquid crystal. As a result, even in the very low external magnetic field (< 10 Oe) the magneto-orientational response increases appreciably. We examine the ferronematic cell with homogeneous planar anchoring in the presence of an external magnetic field perpendicular to the cell planes. If the strength of the ferroparticle-to-director coupling is weak enough, the inverse Frederiks effect can be observed [1,2]. With increase in the magnetic field strength, the nematic reorientation first increases, reaches a maximum and then decreases, disappearing at some critical field. At high fields the nematic director remains undistorted. We present the explanation of this effect, based on the continuum theory of FN. We also present and discuss the results of Monte Carlo simulations of a ferronematic cell. The simulation of the LC host is based on the Gruhn-Hess lattice spin model [3]. Ferroparticles are modeled as spherocylinders interacting with clusters of LC molecules through the pair potential. The results of simulation agree with the continuum theory and demonstrate the inverse Federics effect. We thank Professor T. J. Sluckin for useful discussions. This work was done partially under U. S. Army International Technology Center-Atlantic Grant W911NF-08-1-0037. [1] S.V. Burylov, V.I. Zadorozhnii, I.P. Pinkevich, V.Yu. Reshetnyak and T.J. Sluckin, JMMM 252, 153 (2002). [2] V.I. Zadorozhnii, A.N. Vasilev, V.Yu. Reshetnyak, K.S. Thomas and T.J. Sluckin, Europhys. Lett. 73, 408 (2006). [3] T. Gruhn and S. Hess, Z. Naturforsch. 51a, 1 (1996).  ,-.OQbc    = ݸuiSA"h1?CJOJQJ^JaJmH sH +jh1?CJOJQJU^JaJmH sH h1?CJaJmH sH  hidh ?0JCJaJmH sH +jhidh ?CJUaJmH sH jh ?CJUaJmH sH h ?CJaJmH sH h ?h ?CJaJmH sH h:Lh1?mH sH h1?h1?mH sH h1?h ?mH sH h&6mH sH h ?mH sH hmH sH .c +,$$w$v:$$$$$$$$$$a$gdW$h^h`a$gdW$a$gd1?$a$gd4$7$8$H$`a$gd ?$7$8$H$`a$gd7 $`a$gd7 $`a$gdJ6 $`a$gd$a$gd1?$a$gd ?J= > ? 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