Structural changes in the 6CHBT liquid crystal doped with spherical, rodlike, and chainlike magnetic particles (original) (raw)
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Increasing the magnetic sensitivity of liquid crystals by rod-like magnetic nanoparticles
Magnetic Fréedericksz transition was studied in ferronematics based on the nematic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT). 6CHBT was doped with rod-like magnetic particles of different size and volume concentration. The volume concentrations of magnetic particles in the prepared ferronematics were φ1=10 −4 and φ2=10 −3 . Structural changes were observed by capacitance measurements, which evidenced of a significant influence of the concentration, shape anisotropy and/or the size of the magnetic particles on the magnetic response of these ferronematics.
The Structural Transitions in Liquid Crystals Doped with Fine Magnetic Particles
2001
The stable ferronematics and ferrosmectics (combination of liquid crystals with fine magnetic particles) were prepared for 8CB liquid crystal and magnetic particles 11 nm in diameter. The structural transitions, i.e. magnetic Fredericksz transition, were indicated by means of dielectric and conductivity measurements. The experimental results, i.e. the proof of initial condition n0 ⊥ m0 ( n0 is the director of LC molecules and m0 is the magnetic moment of particles) and the increase of the threshold field of Fredericksz transition vs volume conduction of magnetic particles, are in qualitative agreement with the Burylov and Raikher theory of thermotropic ferronematics.
Liquid crystals doped with magnetic nanoparticles
2009
The paper presents an overview of the observations of structural transitions in ferronematics based on thermotropic nematics 4-cyano-4'octylbiphenyl (8CB) and 4-trans-4’-n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT). The determination of the surface density of anchoring energy of nematic molecules on magnetic particles surfaces by the observations of the structural transitions in external fields is demonstrated on the example of the 8CB-based ferronematic. The ferronematic droplets were observed in solutions of nematogenic 6CHBT dissolved in phenyl isothiocyanate and doped with fine magnetic particles. The phase diagram of the transitions from the isotropic phase to the nematic phase via droplets was found. The magneto-dielectric measurements of various structural transitions in this new system enabled to estimate the type of anchoring of nematic molecules on magnetic particles surfaces in droplets.
Phase Transitions in Liquid Crystal Doped with Magnetic Particles of Different Shapes
International Journal of Thermophysics, 2011
In this study, observations of structural transitions in ferronematics based on the thermotropic nematic 4-trans-4 -n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT) are described. Droplets of the nematic phase in the isotropic phase were observed in solutions of nematogenic 6CHBT dissolved in phenyl isocyanate and 6CHBT dissolved in phenyl isocyanate and doped with magnetic particles of different shapes (nanorods and chain-like particles). Magneto-dielectric measurements of structural transitions in these new systems enable to estimate of the type of anchoring of the nematic molecules on the magnetic particles surface.
International Journal of Thermophysics
We have studied the influence of electric and magnetic fields on the orientational structure of ferronematics based on a thermotropic nematic 4-trans-4'-n-hexylcyclohexyl-isothiocyanato-benzene (6CHBT). The 6CHBT liquid crystal has been dissolved in phenyl isothiocyanate and doped with rod-like or chain-like magnetic particles. In such a mixture, the phase transition from an isotropic to a nematic phase is via a droplet state, i.e., coexistence of nematic and isotropic phases. The obtained results showed that a combination of the electric and magnetic fields can change the character of a phase transition from the isotropic to the nematic phase via the droplet state in such systems. Moreover, magneto-dielectric measurements of structural transitions showed the magnetic field induced a shift of the phase transition temperature from the isotropic to the droplet state.
Effect of Magnetic Particles on Structural Changes and Magneto-Optical Behavior of Liquid Crystal
Acta Physica Polonica A, 2020
Structural changes in the nematic liquid crystal 6CHBT doped with a low concentration (1×10 −4 , 5×10 −4) of magnetic nanorods induced by weak magnetic field in the increasing/decreasing mode, as well as in pulsed regime are investigated using surface acoustic waves and magneto-optical effect. The responses of both surface acoustic waves attenuation and optical transmission of the linearly polarized laser beam (532 nm) passing through the sample were investigated. The role of the concentration of magnetic nanorods on structural changes and corresponding magneto-optical behavior concerning the system stability and switching time under applied field was determined. The obtained results of both methods confirmed an effective orientational coupling between particles' magnetic moments and liquid crystal molecules and showed the effectivity of measurements relying on suspension stability and switching processes.
SAW Investigation of Structural Changes in Liquid Crystals Doped with Magnetic Particles
Acta Acustica united with Acustica, 2018
The surface acoustic waves(SAW) were used to study the effect of magnetic particles on liquid crystals (6CHBT) structural changes in electric and weak magnetic fields using measurements of the attenuation of SAWpropagating along ferronematic liquid crystals. The magnetic nanoparticles in lowv olume concentration (Φ = 1 • 10 −4 , 1 • 10 −5 ,5•10 −5)were added to the liquid crystal during its isotropic phase. In contrast to undoped 6CHTB the distinctive SAWattenuation responses induced by both electric and weak magnetic fields in studied ferronematic liquid crystals have been observed suggesting both structural changes and the orientational coupling between both electric and magnetic moments of magnetic particles and the director of the liquid crystal.
The influence of goethite nanorods on structural transitions in liquid crystal 6CHBT
Journal of Magnetism and Magnetic Materials, 2018
This work is devoted to the study of composite system of liquid crystal 4-(trans-4-n-hexylcyclohexyl)-isothiocyanato-benzene (6CHBT) doped with lathlike goethite magnetic nanoparticles with the concentration of 0.01 vol%. The structural transitions in ferronematic samples were observed by dielectric measurements in a capacitor made of ITO-coated glass electrodes as well as by polarizing optical microscopy. Due to the presence of magnetic particles a decrease of the magnetic Fréedericksz transition was observed. The response of ferronematics to very low magnetic fields is also presented which opens the door towards application possibilities such as low magnetic fields sensors.
The study of structural transitions in liquid crystal droplets doped with magnetic particles
physica status solidi (b), 2006
The magnetically active ferronematic droplets were prepared in solutions of nematic liquid crystal 6CHBT with fine magnetic particles, dissolved in phenyl isocyanate. The phase diagram of the transitions between isotropic, droplet and nematic phases in prepared sample was found. The structural transitions in 6CHBT-based ferronematic and in 6CHBT ferronematic droplets, exposed to external fields, were investigated. The possibility to use the observations of structural transitions for the determination of the type of anchoring of nematic molecules on magnetic particles surfaces was demonstrated. 92 P. Kopčanský et al.: The study of structural transitions in liquid crystal droplets