Electric-field-induced molecular reorientation of a magnetically biased ferronematic liquid-crystal film

Liang, Bau-Jy; Chen, Shu‐Hsia

doi:10.1103/physreva.39.1441

Cited by 64 publications

(34 citation statements)

References 7 publications

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“…As early as 1970, Brochard and de Gennes [2] pointed out that if the colloidal particles possess a permanent magnetic moment, then the orientation of the local moments and the nematic director would be coupled, and this would give rise to some new and interesting physical effects. These systems are known as ferronematics, and further work, both experimental and theoretical, seems to confirm the picture predicted by Brochard and de Gennes [3][4][5].…”

Section: Introductionsupporting

confidence: 63%

Fredericksz Transition Threshold in Nematic Liquid Crystals Filled with Ferroelectric Nano-Particles

Reshetnyak

Shelestiuk

Sluckin

2006

Molecular Crystals and Liquid Crystals

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A key liquid crystalline property for electro-optic applications is the Frederiks threshold electric field. There has been recent experimental interest in liquid crystal-based colloidal suspensions in which the colloidal nanoparticles both possess a permanent electric polarization and provide strong director anchoring on the particle surface. Such suspensions are sometimes known as Filled Liquid Crystals. Our calculations suggest, in qualitative agreement with experiment, that filling the nematic liquid crystal with ferroelectric nanoparticles can significantly decrease the electric Frederiks transition threshold field.

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Section: Introductionsupporting

confidence: 63%

Fredericksz Transition Threshold in Nematic Liquid Crystals Filled with Ferroelectric Nano-Particles

Reshetnyak

Shelestiuk

Sluckin

2006

Molecular Crystals and Liquid Crystals

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“…In such systems aggregated particles produce director distortions extending over macroscopic scales. These suspensions scatter light strongly, and possess unique structural, mechanical, electro-and magneto-optical properties [5,6].Recently, we have shown that even at low concentrations (c part 1%), LC colloids differ strongly from the pure host material [7,8,9,10]. These colloids consist of submicron ferroelectric particles suspended in the LC host.…”

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confidence: 99%

mentioning

confidence: 99%

Orientational Coupling Amplification in Ferroelectric Nematic Colloids

et al. 2006

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We investigated the physical properties of low concentration ferroelectric nematic colloids, using calorimetry, optical methods, infrared spectroscopy and capacitance studies. The resulting colloids normally remain homogeneous, but the nematic orientational coupling is significantly amplified. In particular cases, the nematic orientation coupling increases by 10% for particle concentrations of 0.2%. A manifestation of the increased orientational order is that the clearing temperature of a nematic colloid increases up to 40 Celsius degrees compared to the pure LC host. A theoretical model is proposed in which the ferroelectric particles induce local dipoles whose effective interaction is proportional to the square of the orientational order parameter.PACS numbers: 64.70. Md, 82.70.Dd, Colloids in which the solute is liquid crystalline (LC) are known to possess an extremely rich set of behaviors [1,2,3,4,5]. The anchoring between the LC and microcolloidal particles ( 1µm) can produce long-range orientational distortions around the particles. This results in strong inter-particle interactions -sometimes repulsive and sometimes attractive -in the mesophase. The interactions can give rise to well-ordered structures of particles in the liquid crystal matrix (both lattices and chains) [2,3]. However, in most cases a prerequisite for interesting LC colloidal behavior has been a high concentration dispersion, typically with particle volume fraction c part 30%. In such systems aggregated particles produce director distortions extending over macroscopic scales. These suspensions scatter light strongly, and possess unique structural, mechanical, electro-and magneto-optical properties [5,6].Recently, we have shown that even at low concentrations (c part 1%), LC colloids differ strongly from the pure host material [7,8,9,10]. These colloids consist of submicron ferroelectric particles suspended in the LC host. In these systems, unlike in classic LC colloids, the suspensionmatrix interaction is insufficient to disturb the LC orientation. This small concentration dramatically increases the dielectric anisotropy, significantly decreases the Freedericksz transition voltage, and significantly accelerates electric field-induced director reorientation.In this letter, we report results which show that these phenomena are general properties of liquid crystal suspensions containing ferroelectric colloidal nanoparticles. The addition of impurities normally decreases the nematic clearing temperature T N I [11]. However, our measurements show massive increases in T N I , of the order of 40 • C, for mass impurity concentrations of the order of 0.2%. These results imply an increase in the effective nematic interaction parameter. Measurements of the birefringence, dielectric anisotropy and order parameter in the suspension are consistent with this picture.We have also constructed a theoretical model. The ferroelectric particles in the suspension produce large electric fields in their neighborhood. These electric fields produce induce...

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“…The needles were specially coated to prevent colloidal aggregation, but nevertheless aggregation still occurred. In further work Liang and Chen [6,7] carried out experiments on the magneto-optical effects in magnetic LC composite. It was found that the orientation of suspension of tiny magnetic particles in LC can be notably affected by the magnetic field of the Earth.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Magneto-Optical Properties of Suspensions of Spindle Type Mono-Dispersed Hematite Nano-Particles in Liquid Crystal

Ouskova

Buluy

Blanc

et al. 2010

Molecular Crystals and Liquid Crystals

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We explored how to increase liquid crystal sensitivity to external magnetic fields. Suspensions consisting of a mixture of liquid crystal and spindle type monodispersed hematite nano-particles at concentrations lower than 1 wt% were prepared. The Fréedericksz transition threshold for the suspensions appeared to be lower than for the pure liquid crystal. It was proved that adding canted antiferromagnetic nano-particles in liquid crystals increased their sensitivity to magnetic field while no change of the basic mesogenic properties of the matrix occurred.

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Electric-field-induced molecular reorientation of a magnetically biased ferronematic liquid-crystal film

Cited by 64 publications

References 7 publications

Fredericksz Transition Threshold in Nematic Liquid Crystals Filled with Ferroelectric Nano-Particles

Fredericksz Transition Threshold in Nematic Liquid Crystals Filled with Ferroelectric Nano-Particles

Orientational Coupling Amplification in Ferroelectric Nematic Colloids

Enhanced Magneto-Optical Properties of Suspensions of Spindle Type Mono-Dispersed Hematite Nano-Particles in Liquid Crystal

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