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

Ouskova, E.; Buluy, O.; Blanc, Christophe; Dietsch, Hervé; Mertelj, Alenka

doi:10.1080/15421401003796108

Cited by 27 publications

(17 citation statements)

References 18 publications

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“…[25][26][27][28][29] A small low eld magneto-optic response was observed in a more concentrated suspension, where in most cases the suspensions showed aggregation. [27][28][29] This magneto-optic response is at least two orders of magnitude weaker than the one we observed in the transverse eld.…”

Section: Comparison With Paramagnetic Suspensionsmentioning

confidence: 94%

Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal

et al. 2014

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We have studied the response of ferromagnetic liquid crystals to external magnetic and electric fields, and compared it to the usual response of nematic liquid crystals (NLCs). We have observed effects, which are not present in a pure NLC and are a consequence of the coupling between the nematic director and the magnetization. The electro-optic effect, which is in the ferromagnetic phase the same as in the pure NLC, is accompanied by a converse magnetoelectric effect. The magneto-optic effect differs completely from the one observed in the pure NLC, where it is a quadratic effect and it only appears when a magnetic field larger than a critical field is applied perpendicular to the director. In the ferromagnetic NLC in addition to the response to the perpendicular field, there is also a qualitatively different response to the parallel field. Contrary to the pure NLC no critical field needs to be exceeded for the system to respond to a perpendicular field, but a critical field needs to be exceeded to observe a response to the field parallel to the director and antiparallel to the magnetization. The critical field is in this case two orders of magnitude smaller than the critical field of the magnetic Frederiks transition in the pure NLC. The experimental observations are well described by a simple macroscopic theory.

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Section: Comparison With Paramagnetic Suspensionsmentioning

confidence: 94%

Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal

et al. 2014

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“…For example, ferroelectric nanoparticles have been shown to decrease the Fréedericksz threshold and increase the birefringence of nematics [2,3]. Similarly, ferromagnetic nanoparticles have been used to increase the sensitivity of the host liquid crystals to an applied magnetic field [4,5].…”

Section: Introductionmentioning

confidence: 99%

Gold nanoparticle liquid crystal composites as a tunable nonlinear medium

2014

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We investigate the nonlinearity of a liquid crystal cell doped with gold nanoparticles by considering their selective absorption. Such nonlinearities are promising for optical processing applications and optical limiters. Systems displaying thermal nonlinearities are particularly attractive as the maximum nonlinearity may occur in the absence of an applied field and additionally this nonlinearity can be controlled by the reorientation of the liquid crystal. We show that there exists a theoretical optimum concentration of absorbers, which maximizes the nonlinearity. Further we show that the nonlinearity of the system can be tuned by the reorientation of the liquid crystal host, with the nonlinearity decreasing from 9×10 −5 cm 2 W −1 to zero by the application of a magnetic field of the order of 0.01 Tesla. This allows a fine control of the diffraction efficiency and, in principle, many other nonlinear effects.

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“…We found only few brief mentions about the aggregation and sedimentation of the nanoparticles in LCs in the literature [19][20][21][22]. At the same time, these processes in thermotropic LC matrixes are very strong.…”

Section: Particles Interaction and The Problem Of Colloid Stabilitymentioning

confidence: 99%

“…This explains a tendency of a strong aggregation of the nanotubes in LCs. Herewith the anisotropy of LC matrix leads to formation of aggregates elongated to various degrees and predominantly oriented along the director of an LC [20,22], Figure 12.1a.…”

Section: Particles Interaction and The Problem Of Colloid Stabilitymentioning

confidence: 99%

Ferroelectric Colloids in Liquid Crystals

Reznikov

2012

Liquid Crystals Beyond Displays

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INTRODUCTIONFor many years the science of liquid crystals mostly served the needs of liquid crystal display (LCD) industry; vast majority of funds and human resources were directed to development of numerous LCD modes in nematic liquid crystals (LCs). It was the needs of LCD industry that initiated rapid development of surface LC science, deep studies of correlation between the molecular structures and macroscopic properties of nematic LCs. Studies of more complicated LCs phases and composite LC materials to a large extent have also been initiated by numerous attempts to propose competitive alternative to the traditional nematic LCDs (e.g. PDLCs, bistable LCDs, ferroelectric LCDs). By the beginning of the last decade, the LCD industry has reached such a high level that its further progress has become determined mainly by development of the technology of non-LC components (for example, by fabrication of gigantic highquality glass substrates for the last generation LCDs). This initiated some kind of rebooting of the scientific and mercantile interests of the LC scientific community. There are many sectors of hi-tech industry where LCs have great potentials, such as biotech, telecommunication, and optical processing. The new applications require new materials, sometimes with rather exotic properties, and new technologies. For example, LC materials for telecommunications usually require LCs with strong birefringence but low refractive index, adaptive LC optics needs materials with huge birefringence and low viscosity. Many promising applications of LC for terahertz region are suppressed by a strong absorption of LCs in this region; biotech needs replacement of thermotropic LCs to water-based lyotropic LCs. Tiny and precise patterning of LC alignment over the boundary surfaces becomes crucial for developing new optical elements. All of these new industry needs changed the priority points of LCs science; a number of LCD-related publications steadily decrease in expense of publications on application of LCs in photonics, optical processing, biosensors, and magneto-optics.One of the directions of the development of the modern LCs science is design and study of numerous LC composite materials. Long-distance orientation interaction in mesophase leads to extremely strong influence of a dispersed material on the mesogenic properties of the LC and vice versa; the LC matrix can effectively arrange the positional and translational ordering of the inclusions in the matrix. Therefore, combination of the orientational ordering and relative translation freedom in LCs with properties of the dispersed materials allows scientists to give unique properties to the composite, which are not inherent to its components. In order to obtain synergetic properties, part of the dispersion material in a LC matrix should not be high. Apparently, Brochard and de Gennes [1] first suggested that doping of a nematic LC with elongated submicron ferromagnetic particles in very low volume fraction (f n 10 À3 ) should result in drastic increase of the LC ...

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

Cited by 27 publications

References 18 publications

Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal

Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal

Gold nanoparticle liquid crystal composites as a tunable nonlinear medium

Ferroelectric Colloids in Liquid Crystals

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