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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikiforov A. A., Krylov A. S., Krylova S. N., Gorshkov V. S., Pelegov D. V.
Заглавие : Temperature Raman study of Li4Ti5O12 and ambiguity in the number of its bands
Колич.характеристики :10 с
Место публикации : J. Raman Spectrosc. - 2024. - Vol. 55, Is. 3. - P.406-415. - ISSN 03770486 (ISSN), DOI 10.1002/jrs.6641. - ISSN 10974555 (eISSN)
Примечания : Cited References: 51. - The research was funded by the Russian Science Foundation (project No 22-22-00350, https://rscf.ru/project/22-22-00350)
Аннотация: The two primary physical methods for identifying lithium titanate, a negative electrode material used commercially, are X-Ray diffraction and Raman spectroscopy. Although there are many publications on this topic, they are focused mainly on chemistry, so there are still some points that require clarification from a physical and methodological point of view. Difference of experimentally observed and theoretically predicted Raman spectra was explained through a combination of experiments and computations. The work comprises experiments and computations to explain why there are different numbers of predicted and observed Raman-active bands. Our low-temperature study and the analysis of thermal shifts during heating led us to conclude that the approach with surplus bands is advantageous and we recommend using major F2g band shifts to estimate the sample heating.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ming, Hong, Zhao, Yifei, Zhou, Yayun, Molokeev M. S., Wang, Yuanjing, Song, Enhai, Zhang, Qinyuan
Заглавие : Chemical group substitution enables highly efficient Mn4+ luminescence in heterovalent systems
Место публикации : Adv. Optical Mater. - 2023. - Vol. 11, Is. 10. - Ст.2300076. - ISSN 21951071 (eISSN), DOI 10.1002/adom.202300076
Примечания : Cited References: 36. - This work was financially supported by the National Key Research and Development Program of China (2022YFB3503800), the National Science Foundation of China (Grant Nos. 52202170 and 51972117). This work was also funded by RFBR according to the research project No. 19-52-80003
Аннотация: Defects are a double-edged sword for heterovalent metal-ion doping phosphors. Along with the luminescence tunability of phosphors bestowed by defects, their expected luminescence efficiency would also be inevitably lowered due to the presence of these quenching sites. Herein, a chemical group substitution strategy is proposed, where inorganic polyhedrons act as the smallest chemical units during the structural evolution of the doping process. Such a method can not only effectively prevent the defect generation for charge compensation in heterovalent doping systems, but also facilitate the incorporation of activators into the matrix, leading to extremely high luminescence efficiency. The concept is first confirmed energetically favorable by first-principles simulations. As a robust experimental proof, two newly reported Mn4+-incorporated hexavalent organic-inorganic hybrid oxyfluorides (TMA)2BO2F4:Mn4+ (where TMA stands for tetramethylammonium, and B = W6+ or Mo6+) present high quantum efficiency (up to 94.4%) and short lifetime (down to 2.26 ms) that are superior to the commercial red phosphor K2SiF6:Mn4+ (≈84.8%, ≈8.06 ms). Utilizing the differences in decay lifetimes and thermal quenching behaviors of (TMA)2BO2F4:Mn4+ and K2SiF6:Mn4+, a time- and temperature-resolved single-color multiplexing mode with high-safety and easy-access is developed for information security. This work offers an effective strategy to manipulate defect generation in luminescent materials.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nesterov A. I., Ramirez M. F., Ovchinnikov S. G.
Заглавие : Quench dynamics and defects formation in the Ising chain in a transverse magnetic field
Место публикации : Eur. Phys. J. B. - 2022. - Vol. 95, Is. 4. - Ст.73. - ISSN 14346028 (ISSN), DOI 10.1140/epjb/s10051-022-00331-y
Примечания : Cited References: 36. - AIN acknowledges the support by the CONACyT. The work by SGO is supported by the Russian Scientific Foundation under the grant 18-12-00022
Аннотация: We study quench dynamics and defects formation in the one-dimensional quantum Ising chain in a time-dependent transverse magnetic field, given by a semi-infinite pulse and as the pulse of the finite width. The system’s final state depends on the quench time and pulse amplitude, resulting in the emergence of topological defects, and consists of a mixture of ground and excited states. We obtain a new analytical expression, generalizing the Landau–Zener (LZ) and adiabatic-impulse (AI) approximation formulas for the asymptotic probability of remaining in the ground state. We show that our theoretical predictions are in good agreement with the results of the numerical simulations, even when the LZ and AI approximations fail.
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Вид документа : Статья из журнала
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Автор(ы) : Pankin P. S., Maksimov D. N., Timofeev I. V.
Заглавие : Bound state in the continuum in an anisotropic photonic crystal supported by a full-wave phase plate
Место публикации : J. Opt. Soc. Am. B. - 2022. - Vol. 39, Is. 4. - P.968-972. - ISSN 07403224 (ISSN), DOI 10.1364/JOSAB.451034
Примечания : Cited References: 34. - Council on Grants of the President of the Russian Federation (MK-4012.2021.1.2). The authors are grateful to V.A. Stepanenko (Siberian Federal University) for helpful discussions. P. S. Pankin is grateful for the support of the President of the Russian Federation
Аннотация: We consider bound states in the continuum (BICs) in a 1D multilayered system of an anisotropic defect layer embedded into an anisotropic photonic crystal. We analytically demonstrate that an anisotropic defect layer embedded into anisotropic photonic crystal supports accidental BICs. These BICs can be transformed to high-Q resonances by variation of one of the system's parameters. At the same time, the BICs are remarkably robust in the sense that a true BIC can be recovered by further tuning any of the system's other parameters, leading to tunability of the resonance position.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Orlov V. A., Ivanov A. A., Orlova I. N., Patrin G. S.
Заглавие : Thermally activated drift of magnetic vortices in a random field of defects
Коллективы : Российская академия наук, Физико-технический институт им. Е.К. Завойского ФИЦ Казанского научного центра РАН, Казанский (Приволжский) федеральный университет, Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : VIII Euro-Asian symposium "Trends in magnetism" (EASTMAG-2022): Book of abstracts/ program com. S. G. Ovchinnikov [et al.]. - 2022. - Vol. 1, Sect.: Domain walls, vortices and skyrmions. - Ст.D.O3. - P.368-369. - ISBN 978-5-94469-051-7
Примечания : The study has been carried out within the framework of the state task of the Ministry of Science and Higher Education of the Russian Federation (topic No.FSRZ-2020-0011)
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Прищепа, Оксана Олеговна, Сутормин, Виталий Сергеевич, Крахалев, Михаил Николаевич, Иваненко, Александр Анатольевич, Шефер, Александр Давыдович, Зырянов, Виктор Яковлевич
Заглавие : Азимутальный поворот периодической структуры линейных дефектов в слое холестерика с планарно-коническими граничными условиями
Место публикации : Жидк. крист. и их практич. использ. - 2022. - Т. 22, № 3. - С. 111-115. - ISSN 1991-3966 (ISSN), DOI 10.18083/LCAppl.2022.3.111; Liq. Cryst. Appl. - ISSN 2499-9644 (eISSN)
Примечания : Библиогр.: 7
Аннотация: Исследован процесс формирования периодической структуры линейных дефектов в слое холестерика с планарно-коническими граничными условиями, происходящий под действием электрического поля при релаксации из гомеотропного состояния. Показано, что, прикладывая напряжение в диапазоне 0 ≤ U ≤ 1,8 В, можно получить периодические структуры, ориентированные под различными азимутальными углами в пределах 90°, зависящими от величины поля.Electrically induced azimuthal rotation of periodic structure of linear defects formed within cholesteric layer under planar-conical boundary conditions during relaxation from homeotropic state has been studied. It has been shown that when applying a voltage in the range 0 ≤ U ≤ 1,8 V, the periodic structures oriented at different azimuthal angles (within 90°) depending on the field values can be formed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krakhalev M. N.
Заглавие : Oblique light incidence method to study topological defects in nematic layers with conical boundary conditions
Место публикации : Sci. Rep. - 2021. - Vol. 11, Is. 1. - Ст.17433. - ISSN 2045-2322, DOI 10.1038/s41598-021-96784-9
Примечания : Cited References: 54
Предметные рубрики: CHOLESTERIC FINGERS
DISCLINATIONS
SURFACE
WALLS
ORDER
Аннотация: A polarization microscopy method to investigate the orientational structures and boojums formed in the chiral and achiral nematic layers under conical (tilted) boundary conditions has been developed. Oblique light incidence on nematic layer is used, due to which the phase difference between the ordinary and extraordinary waves depends on the director’s azimuthal angle. The phase difference gets maximal when the director azimuthal angle of achiral nematic φ(x,y)=0 and an azimuthal angle at the center of the chiral nematic layer φ0(x,y)=0 independently of the total twist angle φTOTAL. It has been found that the m=+1 boojums with the phase ξ=±90° and ξ=(−90°+φTOTAL/2) are formed in achiral and chiral nematics, respectively, at the director tilt angle θd/2≅40° at the interface. In addition, the defectless structure of chiral nematic with the periodically variable azimuthal director angle on the substrates has been studied.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Prishchepa O. O., Krakhalev M. N., Rudyak V. Yu., Sutormin V. S., Zyryanov V. Ya.
Заглавие : Periodic structures of linear defects in cholesteric layer with conical-planar anchoring under electric field
Коллективы : "Polarity and Chirality in Soft Matter", International Conference on Ferroelectric Liquid Crystal
Место публикации : 18th International conference on ferroelectric liquid crystals: book of abstracts. - 2021. - Ст.O25
Примечания : Cited References: 4. - This work was supported by the Russian Science Foundation (No. 18-72-10036)
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Parshin A. M., Barannik A. V., Zyryanov V. Ya., Shabanov V. F.
Заглавие : Light interference in a hybrid-aligned nematic layer with nonordered surface disclination lines
Место публикации : J. Opt. Soc. Am. B. - 2020. - Vol. 37, Is. 7. - P.2053-2057. - ISSN 0740-3224, DOI 10.1364/JOSAB.395976. - ISSN 1520-8540(eISSN)
Примечания : Cited References: 19
Предметные рубрики: LIQUID-CRYSTAL
SCATTERING
DEFECTS
DOMAINS
Аннотация: The propagation of a laser beam through a hybrid-aligned nematic layer with a surface disclination line has been investigated. A model of the light interference has been developed to consider the scattering by the structural inhomogeneities. The analytical expression that includes the factor characterizing an exponential decrease in the light scattering has been obtained. The dependence of the intensity of light transmitted through the layer on the magnetic field has been measured. The dependence has been accompanied by the interference oscillations. The theoretical expression is consistent with the experiment, which confirms the correctness of the model concepts.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Паршин, Александр Михайлович, Баранник, Алексей Владимирович
Заглавие : Оптическое пропускание доменной структуры нематика на поверхности полимера в магнитном поле
Место публикации : Жидк. кристаллы и их практич. использ. - 2020. - Т. 20, Вып. 2. - С. 62-68. - ISSN 1991-3966, DOI 10.18083/LCAppl.2020.2.62; Liq. Cryst. Appl.
Примечания : Библиогр.: 20
Предметные рубрики: LIGHT-SCATTERING
DEFECTS
Аннотация: Исследовано распространение лазерного луча через слой гибридно-упорядоченного нематика с поверхностной линией дисклинации, состоящий из доменов с радиальной конфигурацией нематического директора на пленке поликарбоната. Ориентационная структура в объеме домена трансформируется в планарную одноосную, задаваемую линией дисклинации, либо в гомеотропную под действием магнитного поля. Получена зависимость интенсивности света, прошедшего через слой, от магнитного поля, прикладываемого перпендикулярно поверхности полимера. Оптическое пропускание сопровождалось интерференционными минимумами и максимумами. Представлена модель интерференции света, основанная на двулучепреломлении, учитывающая рассеяние на ориентационно-структурных неоднородностях доменного ансамбля. Из рассмотрения свободной энергии жидкого кристалла и эффектов двулучепреломления выведено аналитическое выражение, устанавливающее зависимость между интенсивностью света и напряженностью магнитного поля, совпадающее с экспериментом.The propagation of a laser beam through a layer of a hybrid ordered nematic on a polycarbonate film is studied. The nematic has a surface disclination line consisting of domains with a radial configuration of the nematic director. The orientational structure in the domain volume can be transformed into a planar uniaxial structure defined by a disclination line or into a homeotropic one under the influence of a magnetic field. The dependence of the light intensity transmitted through the layer on the magnetic field applied perpendicular to the polymer surface is obtained. Optical transmission was accompanied by interference minima and maxima. Light interference model based on birefringence which takes into account scattering by the orientation-structural inhomogeneities of the domain ensemble is presented. Considering the analysis of the liquid crystal free energy and the birefringence effects, an analytical expression is derived. It establishes the relationship between the light intensity and the magnetic field strength, which coincides with the experiment.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krakhalev M. N., Prishchepa O. O., Sutormin V. S., Bikbaev R. G., Timofeev I. V., Zyryanov V. Ya.
Заглавие : Electrically induced transformations of defects in cholesteric layer with tangential-conical boundary conditions
Место публикации : Sci. Rep. - 2020. - Vol. 10, Is. 1. - Ст.4907. - ISSN 20452322 (ISSN), DOI 10.1038/s41598-020-61713-9
Примечания : Cited References: 45. - The authors are grateful for the financial support by the Russian Science Foundation (Grant No. 18-72-10036)
Аннотация: Electric-field-induced changes of the orientational structures of cholesteric liquid crystal layer with the tangential-conical boundary conditions have been investigated. The samples with the ratio of the cholesteric layer thickness d to the helix pitch p equalled to 0.57 have been considered. The perpendicularly applied electric field causes a decrease of the azimuthal director angle at the substrate with the conical surface anchoring. In the cells with d = 22 μm, the defect loops having the under-twisted and over-twisted areas are formed. At the defect loop the pair of point peculiarities is observed where the 180° jump of azimuthal angle of the director occurs. Under the action of electric field the loops shrink and disappear. In the cells with d = 13 μm, the over-twisted and under-twisted defect lines are formed. Applied voltage results in the shortening of lines or/and their transformation into a defect of the third type. The director field distribution near defect lines of three types has been investigated by the polarising microscopy techniques. It has been revealed that the length ratio between the over-twisted and third-type defect lines can be controlled by the electric field.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krakhalev M. N., Shabanov V. F., Zyryanov V. Ya.
Заглавие : Point defects in nematic liquid crystal materials with conical anchoring at the interface
Место публикации : Sib. J. Sci. Technol. - 2020. - Vol. 21, Is. 3. - P.433-440. - ISSN 2587-6066, DOI 10.31772/2587-6066-2020-21-3-433-440; \b Сибирский журнал науки и технологий
Примечания : Cited References: 25
Аннотация: The topological point defects in nematic liquid crystal materials have been studied. The method of oblique light incidence has been proposed to determine an azimuthal director angle of an achiral nematic as well as a chiral nematic (cholesteric). The idea of the method is based on the dependence of the optical phase difference between ordinary and extraordinary light beams on the azimuthal director angle at the layer center at oblique incidence of light on a structure in which the polar director angle of a nematic liquid crystal is not equal to 0° or 90° (conical boundary conditions). It has been shown that the phase difference reaches a maximum at a zero azimuthal angle at the center of the layer regardless of the total twist angle of the director. The developed method has been used to analyze topological defects formed in the nematic and cholesteric layers under conical boundary conditions at the interface. The director field distributions of nematic and cholesteric near the surface point defects (boojums) with topological charges m = +1 and m = –1 have been drawn based on the experimental data. The proposed method of oblique light incidence can be used to analyze a wide class of the achiral and chiral liquid crystal media of various types: smectics, nematics, and cholesterics with tilted or hybrid boundary conditions.ГИсследованы топологические точечные дефекты в нематических жидкокристаллических материалах. Предложен метод наклонного падения света, позволяющий определять азимутальный угол директора ахирального нематика, а также закрученного нематика (холестерика). Суть метода состоит в том, что при наклонном падении света на структуру с отличным от 0° и 90° полярным углом директора нематического жидкого кристалла (конические граничные условия) оптическая разность фаз, возникающая между обыкновенным и необыкновенным лучами, определяется величиной азимутального угла директора в центре слоя. Показано, что максимальное значение разности фаз достигается при нулевом азимутальном угле в центре слоя независимо от полного угла закрутки директора. Разработанный метод был использован для анализа топологических дефектов, формирующихся в слоях нематика и холестерика с коническими граничными условиями на межфазной границе. На основании полученных экспериментальных данных были построены распределения поля директора нематика и холестерика вблизи поверхностных точечных дефектов (буджумов) с топологическими зарядами m = +1 и m = –1. Полученные результаты интересны для исследований структурированных материалов, анализа оптическими методами дефектов структур, а предложенный метод наклонного падения света может использоваться для анализа широкого класса ахиральных и хиральных жидкокристаллических сред различного типа: смектиков, нематиков и холестериков с наклонными или гибридными граничными условиями.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov V. A., Patrin G. S., Orlova I. N.
Заглавие : Interaction of a Magnetic Vortex with Magnetic Anisotropy Nonuniformity
Место публикации : J. Exp. Theor. Phys. - 2020. - Vol. 131, Is. 4. - P.589-599. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776120090071
Примечания : Cited References: 51. - This study was supported by the Russian Foundation for Basic Research (project no. 18-02-00161)
Аннотация: The problem of propagation of a magnetic inhomogeneity in the form of a magnetic vortex near a defect simulated by a crystallite with uniaxial anisotropy has been solved theoretically. The defect (crystallite) is implanted into a homogeneous 2D ferromagnetic matrix. Apart from the anisotropy energy, the term responsible for the existence of a centrosymmetric potential is included into the total energy. For calculations, we have used the method of collective variables (Thiele equation). We have considered the variants of bidirectional and unidirectional anisotropy of the crystallite. Analysis of the equations of motion for different directions of the anisotropy axis of the implanted defect has revealed the variety in the behavior of the vortex core as a quasiparticle. The vortex core can be trapped by the defect with equilibrium position of the vortex at rest directly on the crystallite or during its motion at a certain distance from it. It is shown that for a small damping parameter and in the case when the defect anisotropy axis lies in the plane of the magnet, the vortex moves so as if its core experiences the action of the repulsive axially symmetric potential.
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14.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Pugachevskii M.A., Chibisov A.N., Fedorov A. S.
Заглавие : Theoretical and experimental studies of structural defects in CeO2 nanoparticles
Коллективы : Asian School-Conference on Physics and Technology of Nanostructured Materials, Азиатская школа-конференция по физике и технологии наноструктурированных материалов
Место публикации : The Fifth Asian School-Conference on Physics and Technology of Nanostructured Materials: Proceedings. - VLadivostok: Dalnauka Publishing, 2020. - Ст.I.30.06o. - P.45. - ISBN 978-5-8044-1698-1
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krakhalev M. N., Rudyak, Vladimir Yu., Prishchepa O. O., Gardymova, Anna P., Emelyanenko, Alexander V., Liu, Jui-Hsiang, Zyryanov V. Ya.
Заглавие : Orientational structures in cholesteric droplets with homeotropic surface anchoring
Коллективы : Russian Foundation for Basic Research Project [19-53-52011 MNT_a, RFMEFI62117X0011]
Место публикации : Soft Matter. - 2019. - Vol. 15, Is. 28. - P.5554-5561. - ISSN 1744-683X, DOI 10.1039/c9sm00384c. - ISSN 1744-6848(eISSN)
Примечания : Cited References: 67. - This work was supported by the Russian Foundation for Basic Research Project No. 19-53-52011 MNT_a. The research is carried out using the equipment of the shared research facilities of HPC computing resources at Lomonosov Moscow State University supported by the project RFMEFI62117X0011.
Предметные рубрики: LIQUID-CRYSTAL DROPLETS
TOPOLOGICAL DEFECTS
NEMATIC DROPLETS
Аннотация: The dependency of orientational structures in cholesteric droplets with homeotropic surface anchoring on the helicity parameter has been studied by experiment and simulations. We have observed a sequence of structures, in which the director configurations and topological defects were identified by comparison of polarized microscopy pictures with simulated textures. A toron-like and low-symmetry intermediate layer-like structures have been revealed and studied in detail. The ranges of stability of the observed structures have been summarized in a general diagram and explained by the helicity parameter dependence of the free energy terms.
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16.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Rudyak V. Yu., Krakhalev M. N., Gardymova A. P., Prishchepa O. O., Emelyanenko A. V., Zyryanov V. Ya.
Заглавие : Structures, topological defects and optical patterns of cholesteric droplets with homeotropic anchoring
Коллективы : European Conference on Liquid Crystals
Место публикации : 15th Eur. Conf. Liq. Cryst. (ECLC): conf. progr. - 2019. - Ст.PB-31
Примечания : Cited References: 4
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17.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Krakhalev M. N., Rudyak V. Yu., Gardymova A. P., Prishchepa O. O., Emelyanenko A. V., Zyryanov V. Ya.
Заглавие : Structures, topological defects and optical patterns of cholesteric droplets with homeotropic anchoring
Коллективы : International Liquid Crystal Conference
Место публикации : Abstracts of 27th International Liquid Crystal Conference (ILCC 2018). - 2018. - Ст.1-Е-6
Примечания : Cited References: 5
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pyatnov M. V., Vetrov S. Ya., Timofeev I. V.
Заглавие : Localized optical modes in a defect-containing liquid-crystal structure adjacent to the metal
Место публикации : J. Opt. Soc. Am. B: Optical Society of America, 2017. - Vol. 34, Is. 9. - P.2011-2017. - ISSN 07403224 (ISSN), DOI 10.1364/JOSAB.34.002011
Примечания : Cited References: 44. - Russian Foundation for Basic Research (RFBR), Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund (17-42-240464).
Ключевые слова (''Своб.индексиров.''): cholesteric liquid crystals--crystal defects--defects--liquid crystals--liquids--metals--optical kerr effect--polarization--diffraction reflections--external fields--field localization--maximum field intensity--metallic layers--polarization dependence--spectral properties--transmittance spectra--crystal structure
Аннотация: The possibility of the existence of localized optical modes with maximum field intensity at the interface between the metal and cholesteric liquid crystal is theoretically grounded. The system comprises a defect-containing cholesteric liquid crystal and a metal layer. It is established that the localization occurs at almost any defect thickness rather than only at the half-wave thickness, at which the loss of the polarization dependence of diffraction reflection and the absence of field localization are observed for the structure without the metallic layer. It is demonstrated that the spectral properties can be controlled by external fields affecting the liquid crystal. At large thicknesses of the cholesteric liquid crystal between the defect and the metallic layer, the spectrum contains the pronounced peaks corresponding to the edge modes. The results obtained open new opportunities for controlling the transmittance spectrum, polarization, and localization of light in optoelectronic elements based on the investigated system. © 2017 Optical Society of America.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Parshin A. M., Zyryanov V. Ya., Shabanov V. F.
Заглавие : Alignment of liquid crystals by polymers with residual amounts of solvents
Коллективы : Russian Foundation for Basic Research [15-02-06924, 16-53-00073]
Место публикации : Sci. Rep. - 2017. - Vol. 7. - Ст.3042. - ISSN 2045-2322, DOI 10.1038/s41598-017-03243-5
Примечания : Cited References:21. - This work was supported by the Russian Foundation for Basic Research (project No. 15-02-06924 and No. 16-53-00073).
Предметные рубрики: DISCLINATIONS
INTERFACE
DEFECTS
Аннотация: The homogeneous nematic layers in liquid crystal cells with treated surfaces are affected by orientational transitions in the electric, magnetic, or temperature fields. The liquid crystal structures formed on solid or liquid surfaces find limited application in identifying the liquid-crystal states by the textures observed in polarized light. The use of surfaces prepared from polymer solutions makes it possible to significantly broaden the range of application of the liquid crystal structures. We investigate the structures with the continuous transformation of the nematic director orientation from radial to planar, which were formed by the polycarbonate surface in the presence of different residual solvents. The structures contained the disclination lines that aligned either by a plate rubbed to provide the homogeneous planar orientation in the LC layer or by a magnetic field applied along the polycarbonate film during the structure formation. The orientational transitions caused by surface treatment, temperature, and electric or magnetic fields in these structures are observed. The comparison of temperature critical distance as well as electric and magnetic coherence lengths with equilibrium length calculated from the expression for the free energy of the nematic is performed. The electro-optical characteristics of the nematic structures are obtained.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Visotin M. A., Kholtobina A. S., Kuzubov A. A., Mikhaleva N. S., Hsu H. S.
Заглавие : Investigation of intrinsic defect magnetic properties in wurtzite ZnO materials
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2017. - Vol. 440. - P.5-9. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2016.12.130
Примечания : Cited References: 34. - We acknowledge the Siberian Supercomputer Center (SSCC) of SB RAS, Novosibirsk; the Institute of Computational Modeling of SB RAS, Krasnoyarsk; the Joint Supercomputer Center of RAS, Moscow and the ICC of Novosibirsk State University for providing the computing resources. This work was supported by the president of Russia Scientific School program NSh 7559.2016.2 and by the government contract of the Ministry of Education and Science of the Russian Federation to Siberian Federal University (Grant No. 16.1500.2014/K) and RFBR 16–32-60003 mol_a_dk.
Ключевые слова (''Своб.индексиров.''): zno--diluted magnetic semiconductors--defects--thin films--dft calculations--magnetic circular dichroism
Аннотация: Theoretical and experimental investigations of the ferromagnetism induced by intrinsic defects inside wurtzite zinc oxide structures are performed using magnetic field-dependent circular dichroism (MCD-H), direct magnetization measurement (M-H) by superconducting quantum interference device (SQUID) as well as by generalized gradient density functional theory (GGA-DFT). To investigate localized magnetic moments of bulk material intrinsic defects - vacancies, interstitial atoms and Frenkel defects, various-size periodic supercells are calculated. It is shown that oxygen interstitial atoms (Oi) or zinc vacancies (Znv) generate magnetic moments of 1,98 и 1,26 µB respectively, however, the magnitudes are significantly reduced when the distance between defects increases. At the same time, the magnetic moments of oxygen Frenkel defects are large (~1.5–1.8 µB) and do not depend on the distance between the defects. It is shown that the origin of the induced ferromagnetism in bulk ZnO is the extra spin density on the oxygen atoms nearest to the defect. Also dependence of the magnetization of ZnO (101̅0)and(0001) thin films on the positions of Oi and Znv in subsurface layers were investigated and it is shown that the magnetic moments of both defects are significantly different from the values inside bulk material. In order to check theoretical results regarding the defect induced ferromagnetism in ZnO, two thin films doped by carbon (C) and having Zn interstitials and oxygen vacancies were prepared and annealed in vacuum and air, respectively. According to the MCD-H and M-H measurements, the film, which was annealed in air, exhibits a ferromagnetic behavior, while the other does not. One can assume annealing of ZnO in vacuum should create oxygen vacancies or Zn interstitial atoms. At that annealing of the second C:ZnO film in air leads to essential magnetization, probably by annihilation of oxygen vacancies, formation of interstitial oxygen atoms or zinc vacancies. Thus, our experimental results confirm our theoretical conclusions that ZnO magnetization origin are Oi or Znv defects.
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