Weak coupling effects and re-entrant transitions in ferronematic liquid crystals

Zakhlevnykh, A. N.; Petrov, D. A.

doi:10.1016/j.molliq.2014.06.028

Cited by 28 publications

(31 citation statements)

References 41 publications

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“…The present paper is an extension to several studies of LC suspensions doped with dipole (ferromagnetic) particles [39,41–44]. Here we discuss the similarity and difference in the orientational behavior of dipole (ferromagnetic) and quadrupole (diamagnetic) particles in LC suspensions.…”

Section: Resultsmentioning

confidence: 76%

“…When the diamagnetism of the LC matrix ( F 2 ) begins to predominate, at h ≈ h r + , the next transition from the homeotropic phase to the non-uniform state (the angular phase) occurs. A similar diagram was described in [39] for ferronematic liquid crystals. In the case of strong coupling (σ > σ m ), the initial planar phase undergoes a Fréedericksz transition to the non-uniform angular phase with increasing field.…”

Section: Resultsmentioning

confidence: 89%

“…In the magnetized ferronematics (in which the magnetic moments of the ferroparticles are aligned in one direction) with planar coupling of impurity particles to the LC matrix, the magnetic field induces non-threshold Fréedericksz transition for suspensions based on NLC with negative [42] or positive [39] anisotropy of the diamagnetic susceptibility. As we have shown above, in LC suspensions of CNTs this transition has threshold behavior.…”

Section: Resultsmentioning

confidence: 99%

“…For compensated ferronematics the Fréedericksz transition can be only a second-order transition, while for the CNT suspension this transition can be of first or of second order, depending on the segregation parameter. The other feature is that the transition fields for compensated ferronematics depend on the segregation parameter, while for magnetized ferronematics and for LC suspensions of CNTs there is no such dependence [39,42–43]. …”

Section: Resultsmentioning

confidence: 99%

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Magnetic field induced orientational transitions in liquid crystals doped with carbon nanotubes

Petrov¹,

Skokov²,

Zakhlevnykh³

2017

Beilstein J. Nanotechnol.

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We propose a continuum theory of orientational phase transitions induced by an external magnetic field in a suspension of carbon nanotubes in a nematic liquid crystal. It is shown that in a magnetic field a non-uniform and two different uniform phases are possible in the suspension. The uniform phases of the suspension differ by the type of orientational coupling of nanotubes with the liquid crystal matrix (the planar type when the nanotubes are oriented along the matrix director, and the homeotropic type when the nanotubes are perpendicular to the director). The possibility of a redistribution of the nanotube concentration (segregation effect) is shown. The fields of orientational transitions between uniform and non-uniform phases of the suspension are found analytically. It is shown that, when the nanotubes are weakly coupled to the matrix, the magnetic field induces reentrant transitions (uniform planar phase–non-uniform phase–uniform homeotropic phase–non-uniform phase). These transitions can be of first or of second order depending on the carbon nanotubes segregation intensity.

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Magnetic field induced orientational transitions in liquid crystals doped with carbon nanotubes

Petrov¹,

Skokov²,

Zakhlevnykh³

2017

Beilstein J. Nanotechnol.

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“…Для данной геометрии задачи (рис. 2) в работе [15] получено следующее уравнение для порогового поля перехода Фредерикса h c в ФН…”

Section: оценка энергии сцепления магнитных частиц с жидкокристалличеunclassified

Влияние Слабого Сцепления На Магнитный Переход Фредерикса В Ферронематическом Жидком Кристалле

Попов¹,

Гилев²,

Захлевных³

2018

Физика Твердого Тела

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Экспериментально исследован магнитный переход Фредерикса в ферронематике-разбавленной суспензии магнитных наночастиц в нематическом жидком кристалле MBBA. Точка перехода определялась путем диэлектрических измерений емкости в ячейках различной толщины для образцов с различной объемной долей феррочастиц. Изучен эффект слабого сцепления между магнитной и жидкокристаллической подсистемами. Показано, что малые концентрации квазисферических магнитных частиц понижают порог магнитного перехода Фредерикса по сравнению с чистым жидким кристаллом. Проведено теоретическое обоснование полученных результатов. Построена фазовая диаграмма суспензии и предложен способ определения энергии сцепления магнитных частиц с жидкокристаллической матрицей.

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Ferronematic Co(II) Complex: An Active Filler for Magnetically Actuated Soft Materials

Damoc,

Tiron,

Tugui

et al. 2023

Small

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Ferronematics that are generally based on nematic liquid crystals (LCs) doped with magnetic nanoparticles, synergistically taking advantage of the anisotropic and flow characteristics of the nematic host and the magnetic susceptibility of the dopant, have powerful applications as magnetically actuated soft materials. In this work, a Co(II) complex, which alone presents both characteristics, is built with a salen‐type ligand 3,5‐dichlorosubstituted at the aromatic nuclei and has a tetramethyldisiloxane spacer, which makes it one of the few metallomesogens containing this structural motif. Paramagnetic crystals, through heat treatment above 110 °C, change into magnetic nematic LCs. Applying a perpendicular magnetic field of 50 mT, the nematic droplets align two by two through dipole–dipole interactions. By incorporating it into a silicone matrix consisting mainly of polydimethylsiloxane, a 3D printable ink is formulated and crosslinked under various shapes. In this environment, the cobalt complex is stabilized in an LC state at room temperature and, due to its anisotropy, facilitates the mechanical response to magnetic stimuli. The resulting objects can be easily manipulated on fluid or rough surfaces using external magnetic fields, behave like magnets by themselves, and show reversible locomotion.

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Weak coupling effects and re-entrant transitions in ferronematic liquid crystals

Cited by 28 publications

References 41 publications

Magnetic field induced orientational transitions in liquid crystals doped with carbon nanotubes

Magnetic field induced orientational transitions in liquid crystals doped with carbon nanotubes

Влияние Слабого Сцепления На Магнитный Переход Фредерикса В Ферронематическом Жидком Кристалле

Ferronematic Co(II) Complex: An Active Filler for Magnetically Actuated Soft Materials

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