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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M., Korovushkin M. M., Barabanov A. F.
Заглавие : Stability of the superconducting d-wave pairing toward the intersite Coulomb repulsion in CuO2 plane
Место публикации : J. Low Temp. Phys. - 2018. - Vol. 191, Is. 5-6. - P.408-425. - ISSN 00222291 (ISSN), DOI 10.1007/s10909-018-1882-7
Примечания : Cited References: 70. - Acknowledgements The work was supported by the program of the Presidium of the Russian Academy of Sciences No. 12 “Fundamental problems of high-temperature superconductivity”, the Russian Foundation for Basic Research (RFBR) and partly by the Government of Krasnoyarsk Region and the Krasnoyarsk Region Science and Technology Support Fund (Projects Nos. 16-42-243057 and 16-42-240435). The work of A. F. B. was funded by RFBR (Project No. 16-02-00304). The work of M. M. K. was supported by a grant of the President of the Russian Federation (Project MK-1398.2017.2).
Ключевые слова (''Своб.индексиров.''): cuprate superconductors--unconventional superconductivity--spin-charge coupling--spin polarons--intersite coulomb interaction
Аннотация: Taking into account the real crystalline structure of the CuO2 plane and the strong spin-fermion coupling, we study the influence of the intersite Coulomb repulsion between holes on the Cooper instability of the spin-polaron quasiparticles in cuprate superconductors. The analysis shows that only the superconducting d-wave pairing is implemented in the whole region of doping, whereas the solutions of the self-consistent equations for the s-wave pairing are absent. It is shown that intersite Coulomb interaction V1 between the holes located at the nearest oxygen ions does not affect the d-wave pairing, because its Fourier transform Vq vanishes in the kernel of the corresponding integral equation. The intersite Coulomb interaction V2 of quasiparticles located at the next-nearest oxygen ions does not vanish in the integral equations, however, but it is also shown that the d-wave pairing is robust toward this interaction for physically reasonable values of V2.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bludov A. N., Pashchenko V. A., Kobets M. I., Bedarev V. A., Merenkov D. N., Gnatchenko S. L., Gudim I. A.
Заглавие : Antiferromagnetic resonance in crystalline PrFe3(BO3)4
Место публикации : Low Temp. Phys. - 2018. - Vol. 44, Is. 2. - P.139-143. - ISSN 1063-777X, DOI 10.1063/1.5020909. - ISSN 1090-6517(eISSN)
Примечания : Cited References: 18
Аннотация: Experimental AFMR studies of crystalline PrFe3(BO3)4 over a wide frequency range of 10–143 GHz at a temperature of 4.2 K have been carried out. The high-frequency properties of praseodymium ferroborate are well described in terms of a model of a two-sublattice antiferromagnet with an “easy axis” anisotropy. An energy gap of 134.3 ± 0.5 GHz is determined and the magnitude of the effective magnetic anisotropy field is estimated to be 1.9 ± 0.1 kOe. An analysis indicates that the spin-orientational phase transition in this compound is a first order transition.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Mitskan V. A., Dzebisashvili D. M., Barabanov A. F.
Заглавие : Hierarchy of low-energy models of the electronic structure of cuprate HTSCs: The role of long-range spin-correlated hops
Коллективы : Russian fund for fundamental science, Government of the Krasnoyarsk region, Krasnoyarsk regional fund for scientific and technical activity [16-42-240435]; complex program SO RAN [P.2.P, 0356-2015-0405]; RFFI [16-02-00304]
Место публикации : Low Temp. Phys. - 2018. - Vol. 44, Is. 2. - P.130-138. - ISSN 1063-777X, DOI 10.1063/1.5020908. - ISSN 1090-6517(eISSN)
Примечания : Cited References: 42. - This study was conducted with financial support from the Russian fund for fundamental science, Government of the Krasnoyarsk region, Krasnoyarsk regional fund for scientific and technical activity in the framework of Project No. 16-42-240435 as well as the complex program SO RAN No. P.2.P (Project No. 0356-2015-0405). The work of A. F. Barabanov is supported by RFFI (Grant No. 16-02-00304).
Предметные рубрики: HIGH-TC SUPERCONDUCTORS
SINGLE-BAND MODELS
OXIDE SUPERCONDUCTORS
Аннотация: It is shown that for the three-band Emery p–d-model that reflects the real structure of the CuO2-plane of high-temperature superconductors in the regime of strong electron correlations, it is possible to carry out a sequence of reductions to the effective models reproducing low-energy features of elementary excitation spectrum and revealing the spin-polaron nature of the Fermi quasiparticles. The first reduction leads to the spin-fermion model in which the subsystem of spin moments, coupled by the exchange interaction and localized on copper ions, strongly interacts with oxygen holes. The second reduction deals with the transformation from the spin-fermion model to the φ–d-exchange model. An important feature of this transformation is the large energy of the φ–d-exchange coupling, which leads to the formation of spin polarons. The use of this fact allows us to carry out the third reduction, resulting in the t̃ −J̃∗−I-model. Its distinctive feature is the importance of spin-correlated hops as compared to the role of such processes in the commonly used t–J*-model derived from the Hubbard model. Based on the comparative analysis of the spectrum of Fermi excitations calculated for the obtained effective models of the CuO2-plane of high-temperature superconductors, the important role of the usually ignored long-range spin-correlated hops is determined.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Krylova S. N., Krylov A. S., Adamczyk M., Oreshonkov A. S., Shabanov A. V., Vtyurin A. N.
Заглавие : Temperature behavior of BaBi2Nb2O9 ceramics
Коллективы : Joint Russia/CIS/Baltic/Japan Symposium on Ferroelectricity, Young scientists school on the spectroscopic, Физико-технический институт им. А.Ф. Иоффе РАН, Санкт-Петербургский политехнический университет им. Петра Великого
Место публикации : Joint 14th Rus./CIS/Baltic/Japan Symp. on Ferroelectricity (RCBJSF)/ Young sci. school on the spect. studies of critical dynamics at struct. phase trans.: Abstract book/ org. comm. A. N. Vtyurin ; progr. comm. I. N. Flerov. - 2018. - P.181. - ISBN 978-5-9651-1144-2
Примечания : Cited References:
Материалы конференции
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Makarov I. A., Zotova M. V., Ovchinnikov S. G.
Заглавие : Influence of the diagonal and off-diagonal electron-phonon interactions on the formation of local polarons and their band structure in materials with strong electron correlations
Коллективы : Russian Foundation for Basic Research [16-02-00098]; Basic Research Program of the Presidium of the Russian Academy of Sciences [12]
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 126, Is. 5. - P.683-698. - ISSN 1063-7761, DOI 10.1134/S1063776118050059. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 58. - We are grateful to V.I. Zinenko and V.A. Gavrichkov for useful discussions. This work was financially supported by the Russian Foundation for Basic Research (project no. 16-02-00098) and the Basic Research Program no. 12 of the Presidium of the Russian Academy of Sciences ("Fundamental Problems of High-Temperature Superconductivity").
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
D-WAVE SUPERCONDUCTIVITY
LATTICE
Аннотация: For systems with strong electron correlations and strong electron–phonon interaction, we analyze the electron–phonon interaction in local variables. The effects of the mutual influence of electron–electron and electron–phonon interactions that determine the structure of local Hubbard polarons are described. Using a system containing copper–oxygen layers as an example, we consider the competition between the diagonal and off-diagonal interactions of electrons with the breathing mode as the polaron band structure is formed within a corrected formulation of the polaron version of the generalized tight-binding method. The band structure of Hubbard polarons is shown to depend strongly on the temperature due to the excitation of Franck–Condon resonances. For an undoped La2CuO4 compound we have described the evolution of the band structure and the spectral function from the hole dispersion in an antiferromagnetic insulator at low temperatures with the valence band maximum at point (π/2, π/2) to the spectrum with the maximum at point (π, π) typical for the paramagnetic phase. The polaron line width at the valence band top and its temperature dependence agree qualitatively with angle-resolved photoemission spectroscopy for undoped cuprates.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Jiang, Xingxing, Wang, Naizheng, Molokeev M. S., Wang, Wei, Guo, Shibin, Huang, Rongjin, Li, Laifeng, Hu, Zhanggui, Lin, Zheshuai
Заглавие : The anisotropic thermal expansion of non-linear optical crystal BaAlBO3F2 below room temperature
Место публикации : Front. Chem. - 2018. - Vol. 6. - Ст.252. - ISSN 2296-2646, DOI 10.3389/fchem.2018.00252
Примечания : Cited References: 31. - This work was supported by the National Scientific Foundations of China (Grants 11474292, 51702330, 11611530680, 91622118, and 91622124), Russian Foundation for Basic Research (Grant 17-52-53031), the Special Foundation of the Director of Technical Institute of Physics and Chemistry (TIPC) and the Youth Innovation Promotion Association, CAS (outstanding member for ZL and Grant 2017035 for XJ).
Предметные рубрики: LASER
GENERATION
PSEUDOPOTENTIALS
COEFFICIENTS
YAG
Ключевые слова (''Своб.индексиров.''): babf--anisotropic thermal expansion--phonon stimulation--nlo optical--property--low temperature
Аннотация: Thermal expansion is a crucial factor for the performance of laser devices, since the induced thermal stress by laser irradiation would strongly affect the optical beam quality. For BaAlBO3F2 (BABF), a good non-linear optical (NLO) crystal, due to the highly anisotropic thermal expansion its practical applications are strongly affected by the “tearing” stress with the presence of local overheating area around the laser spot. Recently, the strategy to place the optical crystals in low-temperature environment to alleviate the influence of the thermal effect has been proposed. In order to understand the prospect of BABF for this application, in this work, we investigated its thermal expansion behavior below room temperature. The variable-temperature XRD showed that the ratio of thermal expansion coefficient between along c- and along a(b)- axis is high as 4.5:1 in BABF. The Raman spectrum combined with first-principles phonon analysis revealed that this high thermal expansion anisotropy mainly ascribe to progressive stimulation of the respective vibration phonon modes related with the thermal expansion along a(b)- and c-axis. The good NLO performance in BABF can be kept below room temperature. The work presented in this paper provides an in-depth sight into the thermal expansion behavior in BABF, which, we believe, would has significant implication to the manipulation in atomic scale on the thermal expansion of the materials adopted in strong-field optical facility.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gokhfeld D. M.
Заглавие : Magnetization of polycrystalline high-Tc superconductors
Место публикации : High-temperature superconductors: occurrence, synthesis and applications. - New York: Nova Science Publishers, 2018. - P.181-194. - ISBN 9781536133424. - ISBN 9781536133417
Примечания : Cited References: 29
Ключевые слова (''Своб.индексиров.''): critical current--magnetization--pinning force--scaling--surface
Аннотация: Magnetization loops of polycrystalline high-Tc superconductors always are semireversible; they have some asymmetry relative to field axis. These magnetization loops are described successfully by the extended critical state model, which accounts the equilibrium magnetization of the grain surface. The model is applied to determine the intragranular critical current density, the depth of the equilibrium surface region and the grain size from magnetic measurements. The dependence of the critical current density on the magnetic field, the pinning force scaling, the full penetration field and the irreversibility field are discussed.Асимметричные петли намагниченности высокотемпературных сверхпроводников успешно описываются расширенной моделью критического состояния. Внутригранульная плотность критического тока, глубина приповерхностного слоя с равновесной намагниченностью и размер гранул могут быть получены из магнитных измерений.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Smirnova, Ekaterina S., Alekseeva, Olga A., Dudka, Alexander P., Artemov V. V., Zubavichus, Yan V., Gudim I. A., Bezmaternykh L. N., Frolov, Kirill V., Lyubutin, Igor S.
Заглавие : Crystal structure, phase transition and structural deformations in iron borate (Y0.95Bi0.05)Fe3(BO3)4 in the temperature range 90–500 K
Коллективы : Russian Foundation for Basic Research [17-02-00766]; Federal Agency of Scientific Organizations [007-GZ/Ch3363/26]
Место публикации : Acta Crystallogr. B. - 2018. - Vol. 74. - P.226-238. - ISSN 2052-5206, DOI 10.1107/S2052520618002962
Примечания : Cited References:27. - The following funding is acknowledged: Russian Foundation for Basic Research (award No. 17-02-00766) and Federal Agency of Scientific Organizations (Agreement No 007-GZ/Ch3363/26).
Предметные рубрики: HIGH-PRESSURES
GDFE3(BO3)4
SPECTROSCOPY
IFEFFIT
Ключевые слова (''Своб.индексиров.''): rare-earth iron borates--crystal structure--structural phase transition--structural deformations
Аннотация: An accurate X-ray diffraction study of (Y0.95Bi0.05)Fe3(BO3)4 single crystals in the temperature range 90–500 K was performed on a laboratory diffractometer and used synchrotron radiation. It was established that the crystal undergoes a diffuse structural phase transition in the temperature range 350–380 K. The complexity of localization of such a transition over temperature was overcome by means of special analysis of systematic extinction reflections by symmetry. The transition temperature can be considered to be Tstr ≃ 370 K. The crystal has a trigonal structure in the space group P3121 at temperatures of 90–370 K, and it has a trigonal structure in the space group R32 at 375–500 K. There is one type of chain formed by the FeO6 octahedra along the c axis in the R32 phase. When going into the P3121 phase, two types of nonequivalent chains arise, in which Fe atoms are separated from the Y atoms by a different distance. Upon lowering the temperature from 500 to 90 K, a distortion of the Y(Bi)O6, FeO6, B(2,3)O3 coordination polyhedra is observed. The distances between atoms in helical Fe chains and Fe—O—Fe angles change non-uniformly. A sharp jump in the equivalent isotropic displacement parameters of O1 and O2 atoms within the Fe—Fe chains and fluctuations of the equivalent isotropic displacement parameters of B2 and B3 atoms were observed in the region of structural transition as well as noticeable elongation of O1, O2, B2, B3, Fe1, Fe2 atomic displacement ellipsoids. It was established that the helices of electron density formed by Fe, O1 and O2 atoms may be structural elements determining chirality, optical activity and multiferroicity of rare-earth iron borates. Compression and stretching of these helices account for the symmetry change and for the manifestation of a number of properties, whose geometry is controlled by an indirect exchange interaction between iron cations that compete with the thermal motion of atoms in the structure. Structural analysis detected these changes as variations of a number of structural characteristics in the c unit-cell direction, that is, the direction of the helices. Structural results for the local surrounding of the atoms in (Y0.95Bi0.05)Fe3(BO3)4 were confirmed by EXAFS and Mössbauer spectroscopies.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Shneyder E. I., Makarov I. A., Zotova M. V.
Заглавие : Temperature dependent band structure of La2CuO4
Коллективы : Federal Research Center KSC SB RAS, Kirensky Institute of Physics, Research Institute of Agriculture and Ecology of the Arctic, Siberian Federal Univercity
Место публикации : International school/workshop on actual problems of condensed matter physics: Program. Book of abstracts/ ed. S. G. Ovchinnikov. - Norilsk, 2018. - P.25. - ISBN 978-5-904603-08-3
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10.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Muzalevskiy K. V., Ruzicka Z., Zahvatov M. G., Savin I. V., Karavaysky A. Yu.
Заглавие : First use of the Meteor-M No. 2/MTVZA-GYa radiometer for remote sensing of soil moisture and temperature in the Arctic region
Коллективы : Progress in Electromagnetics Research Symposium - Spring 2017 , Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-45-242162]; Program of Presidium of the Russian Academy of Sciences; [SB RAS II.12.1]
Место публикации : Progress in Electromagnetics Research Symposium - Spring: IEEE, 2017. - С. 1426-1429. - ISBN 978-1-5090-6269-0, DOI 10.1109/PIERS.2017.8261971
Примечания : Cited References: 7. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project 16-45-242162, the Program of Presidium of the Russian Academy of Sciences "Arctic" and Program of SB RAS II.12.1.
Аннотация: In this paper, the results of radiothermal remote sensing of moisture and temperature of thawed soil on a test site in the Taymyr Peninsula using full-polarimetric observations of brightness temperature at the frequency of 10.7 GHz are presented. The brightness temperature data were obtained from MTVZA-GYa radiometer on a board of Meteor-M No. 2 satellite with footprint area near the Norilsk city and Khatanga, the Russia Federation. The MTVZA-GYa data covered the period from January 1 to December 31, 2015. The method to retrieve the soil moisture and temperature was based on solving an inverse problem by minimizing the norm of the residuals between the observed and predicted values of the brightness temperature. The calculation of the brightness temperature was performed using a semi-empirical model of radio-thermal emission the parameters of which have been pre-calibrated at the test sites in the area of Norilsk and Khatanga, as well as using a soil dielectric model with high in organic matter. The dielectric model was especially designed based on laboratory measurements of the complex permittivity of the organic-rich soil samples, which were collected at the test site near Norilsk city. As a result, the values of the root-mean-square error between the retrieved and measured soil temperatures and soil moisture were not exceed 6.5o 0.06cm3/cm3, respectively for both test sites. These results indicate the perspectives of using the full-polarimetric observations of MTVZA-GYa radiometer on a board of Meteor-M No. 2 satellite in the X-band for the purpose of measuring the soil temperature and soil moisture in the Arctic region.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Tarasov I. A., Rautskii M. V., Yakovlev I. A., Volochaev M. N.
Заглавие : Effect of epitaxial alignment on electron transport from quasi-two-dimensional iron silicide α-FeSi2 nanocrystals into p-Si(001)
Коллективы : International Symposium on Nanostructures - Physics and Technology , Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-42-243060, 16-42-243035]; Russian Foundation for Basic Research, Government of the Republic of Khakassia [17-42-190308]
Место публикации : Semiconductors. - 2018. - Vol. 52: 25th International Symposium on Nanostructures - Physics and Technology (Jun 26-30, 2017, Saint Petersburg, Russia), Is. 5. - P.654-659. - ISSN 1063-7826, DOI 10.1134/S1063782618050330. - ISSN 1090-6479(eISSN)
Примечания : Cited References:31. - The work was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research projects no. 16-42-243060 and 16-42-243035 and Russian Foundation for Basic Research, Government of the Republic of Khakassia, research project no. 17-42-190308. We also thank L.A. Solovyov for his assistance in XRD analysis.
Предметные рубрики: BETA-FESI2 THIN-FILMS
LOW-TEMPERATURE
GROWTH
FESI2
SI(100)
SI(111)
Аннотация: Self-assembled growth of α-FeSi2 nanocrystal ensembles on gold-activated and gold-free Si(001) surface by molecular beam epitaxy is reported. The microstructure and basic orientation relationship (OR) between the silicide nanocrystals and silicon substrate were analysed. The study reveals that utilisation of the gold as catalyst regulates the preferable OR of the nanocrystals with silicon and their habitus. It is shown that electron transport from α-FeSi2 phase into p-Si(001) can be tuned by the formation of (001)-or (111)-textured α-FeSi2 nanocrystals ensembles. A current-voltage characteristic of the structures with different preferable epitaxial alignment (α-FeSi2(001)/Si(100) and α-FeSi2(111)/Si(100)) shows good linearity at room temperature. However, it becomes non-linear at different temperatures for different ORs due to different Schottky barrier height governed by a particular epitaxial alignment of the α-FeSi2/p-Si interfaces.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zheng Y., Zhang H., Zhang H., Xia Z., Liu Y., Molokeev M. S., Lei B.
Заглавие : Co-substitution in Ca1−xYxAl12−xMgxO19 phosphors: local structure evolution, photoluminescence tuning and application for plant growth LEDs
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 15. - P.4217-4224. - ISSN 20507534 (ISSN), DOI 10.1039/c8tc00165k
Примечания : Cited References: 47. - The present work was supported by the National Natural Science Foundation of China (Grant No. 21671070), the Project for Construction of High-level University in Guangdong Province, and the Teamwork Projects funded by the Guangdong Natural Science Foundation (Grant No. S2013030012842), and the Guangzhou Science & Technology Projects (No. 201704030086, 201605030005), and the reported study was funded by the RFBR according to the research project 17-52-53031. Special Funds for the Cultivation of Guangdong College Students’ Scientific and Technological Innovation (‘‘Climbing Program’’ Special Funds) were granted for Dr Yinjian Zheng.
Ключевые слова (''Своб.индексиров.''): co substitution--crystal structure transformation--high temperature solid-state reaction--lighting systems--local structure--luminescence measurements--structural refinement--tunable luminescences
Аннотация: Herein, Mn4+-activated Ca1-xYxAl12-xMgxO19 (x = 0-0.50) solid solutions were prepared using a conventional high-temperature solid-state reaction. Crystal structure transformation via chemical co-substitution of Y3+/Mg2+ for Ca2+/Al3+ was investigated in detail. The optical properties of Ca1-xYxAl12-xMgxO19 (x = 0-0.50) have been reported for the first time using a combination of techniques including structural refinement and luminescence measurements. Co-doping of Mg and Y cations within the CaAl12O19 host in a controlled manner resulted in the as-prepared samples with red/far-red ratio-tunable luminescence properties. The emission bands well-matched with the absorption band of phytochrome. Interestingly, enhanced Mn4+ luminescence can be obtained upon the addition of Mg2+ and Y3+. Unexpectedly, the quantum yields exhibit a slight change when x is in the range from 0.05 to 0.40; this indicates that these solid solutions have significant potential as lighting systems for plant growth.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Deng J., Zhang H., Zhang X., Molokeev M. S., Qiu J., Liu Y., Lei B., Ma L., Wang X.
Заглавие : Enhanced luminescence performance of CaO:Ce3+,Li+,F- phosphor and its phosphor-in-glass based high-power warm LED properties
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 15. - P.4077-4086. - ISSN 20507534 (ISSN), DOI 10.1039/c8tc00813b
Примечания : Cited References: 44. - The present study was supported by the National Natural Science Foundation of China (Grant No. 21671070), the Project for Construction of High-level University in Guangdong Province, the Teamwork Projects funded by the Guangdong Natural Science Foundation (Grant No. S2013030012842), the Guangzhou Science & Technology Project (No. 201704030086) and the Open Project Fund from Key Laboratory of Advanced of Materials of Yunnan Province (No. 2018KF01).
Ключевые слова (''Своб.индексиров.''): correlated color temperature--critical concentration--doping concentration--enhanced luminescence--high color rendering index--high power white led--high temperature solid-state reaction--thermal and chemical stabilities
Аннотация: To obtain white light-emitted diodes (wLEDs) with a low correlated color temperature (CCT) and a high color rendering index (CRI), red-emission is indispensable in their emission spectra. Herein, CaO:Ce3+,Li+,F- yellow phosphors with more red spectral component have been prepared via a high temperature solid-state reaction. As compared to the F- undoped samples, CaO:Ce3+,Li+,F- phosphor have lower critical doping concentration of Ce3+ and show stronger luminescence. At the critical concentration, a quantum efficiency of 66.4% and enhanced thermal and chemical stability were obtained in CaO:Ce3+,Li+,F-. Furthermore, a CaO:Ce3+,Li+,F--based phosphor-in-glass (PiG) using the red-emitting glass system with the composition of SiO2-Na2CO3-Al2O3-CaO:Eu3+ as the host material was constructed and used for high-power white LED applications. Such PiG samples with different phosphor doping concentrations can satisfy various light color demands and display higher reliability than the CaO:Ce3+,Li+,F- phosphor. An optimal PiG-based wLED exhibits color coordinates of (0.3769, 0.3386), a CCT of 3774 K, a CRI of 82.5 and a LE of 73.1 when the mass ratio of phosphor to glass matrix was 7:50 in PiG. Moreover, such PiG-based wLED also showed acceptable color stability under different drive currents. All the above results demonstrate that CaO:Ce3+,Li+,F- can be expected to be a potential alternative yellow phosphor for blue light excited PiG based warm wLEDs, particularly for high-power devices.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Balaev D. A.
Заглавие : Temperature behavior of the magnetoresistance hysteresis in a granular high-temperature superconductor: Magnetic flux compression in the intergrain medium
Место публикации : Physica C. - 2018. - Vol. 550. - P.19-26. - ISSN 09214534 (ISSN), DOI 10.1016/j.physc.2018.04.005
Примечания : Cited References: 56. - The work was supported by the Russian Science Foundation (Grant No. 17-72-10050 ).
Ключевые слова (''Своб.индексиров.''): barium compounds--copper compounds--grain boundaries--hysteresis--magnetic flux--magnetic moments--magnetization--magnetoresistance--yttrium barium copper oxides
Аннотация: Granular high-temperature superconductors (HTSs) are characterized by the hysteretic behavior of magnetoresistance. This phenomenon is attributed to the effective field in the intergrain medium of a granular HTS. At the grain boundaries, which are, in fact, weak Josephson couplings, the dissipation is observed. The effective field in the intergrain medium is a superposition of the external field and the field induced by magnetic moments of HTS grains. Meanwhile, analysis of the field width of the R(H) magnetoresistance hysteresis ΔH = Hdec − Hinc at Hdec = const, where Hinc and Hdec are increasing and decreasing branches of the R(H) hysteretic dependence, shows that the effective field in the intergrain medium exceeds by far both the external field and the field induced by magnetic moments of HTS grains. This situation suggests the magnetic flux compression in the intergrain medium because of the small length of grain boundaries, which amounts to ∼1 nm, i.e., is comparable with the coherence length and corresponds to Josephson tunneling in HTS materials. In this work, using the previously developed approach, we examine experimental data on the magnetoresistance and magnetization hysteresis in the granular YBa2Cu3O7 HTS compound in the range from 77 K to the critical temperature. According to the results obtained, the degree of magnetic flux compression determined by the parameter α in the expression for the effective field Beff(H) = H − 4π M(H) α in the intergrain medium remains constant over the investigated temperature range. All the features of the observed evolution of the R(H) hysteretic dependences are explained well within the proposed approach when the expression for Beff(H) contains the experimental M(H) magnetization data and the parameter α of about 20–25. The latter is indicative of the dominant effect of magnetic flux compression in the intergrain medium on the transport properties of granular HTS materials.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Аверьянов, Евгений Михайлович
Заглавие : Температурные зависимости показателей преломления одноосных каламитных жидких кристаллов с высоким двупреломлением
Место публикации : Жидк. кристаллы и их практич. использ. - 2018. - Т. 18, № 2. - С. 53-63. - ISSN 1991-3966, DOI 10.18083/LCAppl.2018.2.53; Liq. Cryst. Appl.
Примечания : Библиогр.: 29
Предметные рубрики: PHASE-TRANSITION
ORIENTATIONAL ORDER
ISOTROPIC LIQUID
MOLECULES
Ключевые слова (''Своб.индексиров.''): жидкие кристаллы--температурные зависимости показателей преломления--liquid crystals--temperature dependences of the refractive indices
Аннотация: Температурные зависимости показателей преломления nj(t) и величин n(t) = (n|| + 2n⊥)/3, n(t) =ε-1/2, ε= (ε|| + 2ε⊥)/3, εj = nj2 для световых волн с поляризацией вдоль (j = ||) и нормально директору (j = ⊥) в одноосных каламитных жидких кристаллах (ЖК) исследованы в рамках микроскопического подхода с учетом анизотропии тензора локального поля fj(t) =1 + Lj(t)[εj(t)–1] и тензора Лорентца Lj(t). Показано, что известные отрицательные производные n(t)' = dn(t)/dt, n' и точка to минимума на зависимости n⊥(t) в каламитных ЖК отвечают малым и средним значениям двупреломления Δn = n|| – n⊥. Для ЖК с высокими величинами Δn и компонентами L⊥, превышающими пороговое значение L⊥e(nj), предсказаны два новых эффекта: положительные значения n', и наличие точки te максимума на зависимости n||(t). Для ряда нематиков с высокими значениями Δn определены компоненты Lj(t), подтверждено наличие предсказанных эффектов и условий их проявления, получены значения te и прослежена их связь с величиной Δn. Выяснены особенности перехода от ЖК с точкой to к ЖК с точкой te по мере роста Δn.The temperature dependences of the refractive indices nj(t) and the values n(t) = (n|| + 2n⊥)/3, n(t) =ε-1/2, ε= (ε|| + 2ε⊥)/3, εj = nj2 for the light waves polarized along (j = ||) and across (j = ⊥) the director in uniaxial calamitic liquid crystals (LCs) were studied within the microscopic approach with taking into account the anisotropy of the local-field tensor fj(t) =1 + Lj(t)[εj(t)–1] and the Lorentz tensor Lj(t). The known negative derivatives n(t)' = dn(t)/dt, n' and the point to of minimum at the dependence n⊥(t) for calamite LCs were shown to correspond to small and medium values of the birefringence Δn = n|| – n⊥. For LCs with high values of δn and components L⊥ exceeding the threshold value L⊥e two new effects were predicted: positive derivatives n', and the presence of the point te of maximum at the dependence n||(t). For a number of nematics with high values of Δn the components Lj(t) were determined, the presence of the predicted effects and the conditions for their manifestation were confirmed, the values te were obtained and their connection with the magnitude Δn were established. The features of the transition from LCs with point to to LCs with point c under gradual increase in Δn were cleared up.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M.
Заглавие : Effect of gap anisotropy on the spin resonance peak in the superconducting state of iron-based materials
Коллективы : Presidium of RAS Program for the Fundamental Studies [12]; Foundation for the advancement of theoretical physics and mathematics "BASIS"; Gosbudget Program [0356-2017-0030]
Место публикации : Phys. Rev. B. - 2018. - Vol. 98, Is. 10. - Ст.104510. - ISSN 2469-9950, DOI 10.1103/PhysRevB.98.104510. - ISSN 2469-9969(eISSN)
Примечания : Cited References:90. - I would like to thank I. Eremin, S.A. Kuzmichev, and T.E. Kuzmicheva for useful discussions. This work was supported in part by Presidium of RAS Program for the Fundamental Studies No. 12, Gosbudget Program No. 0356-2017-0030, and Foundation for the advancement of theoretical physics and mathematics "BASIS".
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTIVITY
FE-BASED SUPERCONDUCTORS
Аннотация: Spin resonance in the superconducting state of Fe-based materials within the multiorbital model with unequal anisotropic gaps on different Fermi surface sheets is studied. On the basis of the model gap function and the one calculated within the spin fluctuation theory of pairing, I show that the resonance peak shifts to higher frequencies with increasing the zero-amplitude gap magnitude. On the contrary, with increasing the gap anisotropy, it shifts to lower frequencies and loses some intensity.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Музалевский, Константин Викторович, Михайлов, Михаил Иванович
Заглавие : Измерение влажности и температуры почвы на основе интерференционного приёма линейно-поляризованных сигналов ГЛОНАСС и GPS
Место публикации : Совр. пробл. дистан. зондир. Земли из космоса. - 2018. - Т. 15, № 4. - С. 155-165. - ISSN 20707401 (ISSN), DOI 10.21046/2070-7401-2018-15-4-155-165
Примечания : Библиогр.: 18. - Исследование выполнено при финансовой поддержке Российского фонда фундаментальных исследований (проекты No 18-05-00405, 0356-2018-0060), а также Программы II.12.1. «базовых» фундаментальных исследований СО РАН.
Ключевые слова (''Своб.индексиров.''): глобальные навигационные спутниковые системы--глонасс--gps--рефлектометрия--влажность почвы--температура почвы--сельскохозяйственные почвы--арктические тундровые почвы--global navigation satellite systems--glonass--gps--reflectometry--soil moisture--soil temperature--agricultural soils--arctic tundra soils
Аннотация: В данной работе представлены результаты теоретического исследования возможностей дистанционного зондирования влажности талой сельскохозяйственной, влажности и температуры мёрзлой тундровой почв на основе измерения отношения коэффициентов отражения линейно-поляризованных волн (поляризационный индекс) из интерференционных диаграмм сигналов ГЛОНАСС и GPS, регистрируемых вблизи поверхности Земли на частотах 1,2 и 1,6 ГГц. В приближении метода Кирхгофа оценены диапазоны углов возвышения спутников над горизонтом (0–55°), в пределах которых существенна доля когерентной составляющей над диффузной при рассеянии в зеркальном направлении сигналов ГЛОНАСС и GPS шероховатой поверхностью почвенного покрова. В ходе решения прямой задачи моделировался «измеренный» поляризационный индекс отражённых волн (с добавлением случайной величины, распределённой по нормальному закону) на двух частотах 1,2 и 1,6 ГГц с использованием типичных профилей влажности и температуры естественно сложенных почв. Показано, что поляризационный индекс недостаточно чувствителен для восстановления слоистой структуры влагосодержания в талой и температуры в мёрзлой почвах на фоне шумов (1,5–2 дБ) регистрируемых интерференционных диаграмм. Обратная задача по восстановлению влажности и температуры почвы из «измеренного» поляризационного индекса решалась в приближении диэлектрически-однородного почвенного полупространства. Показано, что для всех рассмотренных профилей вне зависимости от используемой частоты сигналов максимальная погрешность восстановления влажности и температуры почвы не превышает 0,03 см3/см3 и 1 °С относительно соответствующих средних величин, рассчитанных для поверхностного слоя почвы 1 см.This paper presents the results of a theoretical study of the potential for remote sensing of moisture of agricultural thawed soil, moisture and temperature in tundra frozen soil based on measurement of the ratio between reflection coefficients on linear-orthogonal polarizations (polarization index) from the interference patterns of GLONASS and GPS signals recorded near the Earth's surface at frequencies of 1.2 and 1.6 GHz. The ranges of satellites elevation angles within which the coherent component exceeds the diffuse part in the mirror scattering of GLONASS and GPS signals by the surface roughness were estimated by Kirchhoff's method. In the course of solving the direct problem, the "measured" polarization index of reflected waves was simulated (with addition of a random variable distributed according to the normal law) at two frequencies of 1.2 and 1.6 GHz using typical moisture and temperatures profiles of soils. It is shown that the polarization index is not sensitive enough to retrieve the layered structure of moisture in thawed and temperature profile in frozen soil, against the background noise (1.5-2 dB) of the recorded interference diagrams. The inverse problem of soil moisture and soil temperature retrieval from the "measured" polarization index was solved in the approximation of dielectrically-homogeneous half-space. It is shown that for all the profiles examined, regardless of frequency of GNSS signals, the maximum error in soil moisture and soil temperature retrieval does not exceed 0.03 cm3/cm3 and 1 °C, relative to the corresponding average values calculated for the topsoil of 1 cm.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shestakov V. A., Korshunov M. M., Dolgov O. V.
Заглавие : Temperature-dependent s± ↔ s++ transitions in the multiband model for Fe-based superconductors with impurities
Коллективы : Russian Foundation for Basic Research [16-02-00098]; Presidium of RAS Program for the Fundamental Studies [12]; "BASIS" Foundation for Development of Theoretical Physics and Mathematics; Gosbudget program [0356-2017-0030]
Место публикации : Symmetry. - Basel, 2018. - Vol. 10, Is. 8. - Ст.323. - ISSN 2073-8994, DOI 10.3390/sym10080323
Примечания : Cited References: 50. - This work was supported in part by the Russian Foundation for Basic Research (grant 16-02-00098), Presidium of RAS Program for the Fundamental Studies #12, and "BASIS" Foundation for Development of Theoretical Physics and Mathematics. MMK acknowledges support by the Gosbudget program #0356-2017-0030.
Предметные рубрики: IRON-BASED MATERIALS
Ключевые слова (''Своб.индексиров.''): unconventional superconductors--iron pnictides--iron chalcogenides--impurity scattering
Аннотация: We study the dependence of the superconducting gaps on both the disorder and the temperature within the two-band model for iron-based materials. In the clean limit, the system is in the s± state with sign-changing gaps. Scattering by nonmagnetic impurities leads to the change of the sign of the smaller gap, resulting in a transition from the s± to the s++ state with the sign-preserving gaps. We show here that the transition is temperature-dependent. Thus, there is a line of s±→s++ transition in the temperature–disorder phase diagram. There is a narrow range of impurity scattering rates, where the disorder-induced s±→s++ transition occurs at low temperatures, but then the low-temperature s++ state transforms back to the s± state at higher temperatures. With increasing impurity scattering rate, the temperature of such s++→s± transition shifts to the critical temperature Tc, and only the s++ state is left for higher amounts of disorder.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Аверьянов, Евгений Михайлович
Заглавие : Температурное поведение показателей преломления дискотических нематиков с высоким двупреломлением
Место публикации : Жидк. кристаллы и их практич. использ. - 2018. - Т. 18, № 3. - С. 37-44. - ISSN 1991-3966, DOI 10.18083/LCAppl.2018.3.37; Liq. Cryst. Appl. - ISSN 2499-9644
Примечания : Библиогр.: 29
Предметные рубрики: IN-SITU PHOTOPOLYMERIZATION
LIQUID-CRYSTALS
ANISOTROPIC FILMS
Ключевые слова (''Своб.индексиров.''): дискотические нематики--температурное поведение показателей преломления--discotic nematics--temperature behavior of refractive indices
Аннотация: Температурное поведение показателей преломления nj(t) и величин n(t) = (n|| + 2n⊥)/3, n(t) = ε1/2, ε = (ε|| + 2ε⊥)/3, εj = nj2 для световых волн с поляризацией вдоль (j = ||) и нормально директору (j = ⊥) в дискотических нематиках ND исследовано в рамках микроскопического подхода с учетом анизотропии тензора локального поля fj(t) =1 + Lj(t)[εj(t) – 1] и тензора Лорентца Lj(t). Показано, что известные отрицательные производные n(t)' = dn(t)/dt, и точка te минимума на зависимости n||(t) в нематиках ND отвечают малым и средним значениям двупреломления Δn = n|| – n⊥. Для ЖК с высокими величинами Δn и компонентами L⊥, меньшими порогового значения Δn(to), предсказаны два новых эффекта: положительные значения n',n', и наличие точки максимума to на зависимости n⊥(t). Установлена связь to с величиной Δn(to) и зависимостью Δn(λ) от длины световой волны λ. Выяснены особенности перехода от объектов с точкой te к объектам с точкой to по мере роста Δn. Указаны молекулы, для которых можно ожидать наличия предсказанных эффектов. Отмечена роль этих эффектов в улучшении визуальных характеристик дисплеев с нематиком ND в граничной компенсирующей пленке.Temperature behavior of refractive indices nj(t) and values of n(t) = (n|| + 2n⊥)/3, n(t) = ε1/2, ε= (ε|| + 2ε⊥)/3, εj = nj2 for the light waves polarized along (j = ||) and across (j = ⊥) the director in discotic nematics ND was studied within the microscopic approach with accounting for the anisotropy of the local-field tensor fj(t) =1 + Lj(t)[εj(t) – 1] and the Lorentz tensor Lj(t). The known negative derivatives n(t)' = dn(t)/dt, and the point te of minimum at the dependence n||(t) for nematics ND were shown to correspond to small and medium values of the birefringence Δn = n|| – n⊥. For nematics ND with high values of Δn and components L⊥ less than the threshold value L⊥o(nj), two new effects were predicted: positive derivatives n',n' and the presence of the maximum point to at the dependence n⊥(t). The correlation of to with the magnitude of Δn(to) and the dependence Δn(λ) on the light wavelength λ was established. The features of the transition from objects with point te to objects with point to under gradual increase of Δn were cleared up. The molecules were pointed for which one could expect the presence of the predicted effects. The role of these effects in the improvement of visual characteristics of liquid crystal displays with nematic ND in the boundary compensation film was observed.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wu, Po-Chang, Chen, Hsin-Li, Rudakova, Natalya V., Timofeev I. V., Zyryanov V. Ya., Lee, Wei
Заглавие : Electro-optical and dielectric properties of polymer-stabilized blue phase liquid crystal impregnated with a fluorine-containing compound
Коллективы : Ministry of Science and Technology, Taiwan [104-2112-M-009-008-MY3, 106-2923-M-009-002-MY3]; Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-42-240704, 17-42-240464]
Место публикации : J. Mol. Liq. - 2018. - Vol. 267. - P.138-143. - ISSN 0167-7322, DOI 10.1016/j.molliq.2017.12.062. - ISSN 1873-3166(eISSN)
Примечания : Cited References: 47. - The authors are indebted to Prof. Mon-Juan Lee of Chang-Jung Christian University for valuable discussions on photopolymerization. This work was financially supported by the Ministry of Science and Technology, Taiwan, through Grant Nos. 104-2112-M-009-008-MY3 and 106-2923-M-009-002-MY3, and by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research projects 16-42-240704 and 17-42-240464.
Предметные рубрики: HYSTERESIS
TEMPERATURE
MONOMERS
Ключевые слова (''Своб.индексиров.''): polymer-stabilized blue phase--liquid crystal--fluorine-containing--compound--operating voltage--ionic effect
Аннотация: The effects of a fluorine-containing compound (4,4′-difluorobenzophenone; DF) on the electro-optical and dielectric properties of polymer-stabilized blue phase (PSBP) liquid crystals were investigated. When a PSBP cell was driven by an in-plane electric field, the addition of DF up to 2.7 wt% effectively reduced the operation voltage by ~ 30%. Further inspection by dielectric spectroscopy indicated that the ionic concentration in PSBP decreased with increasing loading of DF. This finding can be ascribed to the complexation of impurity ions near the ketone group and carbon–fluorine bonds of the DF compound that restrained the ion transport after photopolymerization. As a result, the DF compound can be regarded as a superior ion-suppressor, enabling the reduction in the ionic effect and, in turn, the promotion of the electro-optical response of a PSBP.
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