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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G.
Заглавие : Ab initio calculation of the ferroelectric phase transition in disordered and ordered PbSc0.5Ta0.5O3 and PbSc0.5Nd0.5O3 solid solutions with the use of a model Hamiltonian
Разночтения заглавия :авие SCOPUS: Ab initio calculation of the ferroelectric phase transition in disordered and ordered PbSc0.5Ta0.5O3 and PbSc 0.5Nd0.5O3 solid solutions with the use of a model Hamiltonian
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 106, Is. 3. - P542-549. - ISSN 1063-7761, DOI 10.1134/S1063776108030138
Примечания : Cited References: 17
Предметные рубрики: RELAXOR FERROELECTRICS
PEROVSKITES
BATIO3
PBTIO3
Ключевые слова (''Своб.индексиров.''): approximation theory--ferroelectric materials--hamiltonians--mathematical models--monte carlo methods--phase transitions--ferroelectric phase transition--gordon-kim model--local-mode approximation--solid solutions
Аннотация: To describe the ferroelectric phase transition in ordered and disordered PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nd0.5O3 (PSN) solid solutions, a model Hamiltonian is written in the local-mode approximation, in which long-range dipole-dipole and short-range interactions of local modes are taken into account. The Hamiltonian parameters are determined from the set of energies of a series of distorted structures, calculated within the nonempirical generalized Gordon-Kim model. The statistical mechanics of the systems with a model Hamiltonian is investigated by the Monte Carlo method. It is revealed that PSN solid solutions undergo a transition to the ferroelectric rhombohedral phase through an intermediate phase, existing in a narrow temperature range. PST solid solutions undergo a ferroelectric phase transition directly from the paraelectric cubic to the ferroelectric rhombohedral phase.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zinenko V. I.
Заглавие : Ab initio investigation of the magnetic and ferroelectric properties of double perovskites LaPbMeSbO6 (Me = Mn, Fe, Co, Ni)
Коллективы : Russian Foundation for Basic Research [12-02-00025-a], Russian Federation [NSh-924-2014.2]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 57, Is. 5. - P.983-991. - ISSN 1063, DOI 10.1134/S1063783415050340. - ISSN 10906460(eISSN)
Примечания : Cited References:19. - This study was supported by the Russian Foundation for Basic Research (project no. 12-02-00025-a) and the Council on Grants from the President of the Russian Federation in Support of the Leading Scientific Schools (grant no. NSh-924-2014.2). Calculations were performed on supercomputers of the National Research Centre "Kurchatov Institute" (Moscow, Russia).
Аннотация: The results of ab initio calculations of the ferroelectric and magnetic properties of the recently synthesized double perovskites LaPbMeSbO6 (Me (2+) = Mn2+, Fe2+, Co2+, Ni2+) have been presented. The ordered double perovskites with a layered ordering of cations A and A' and a checkerboard ordering of cations B and B' have been considered. The calculation of the lattice dynamics has revealed instabilities in the phonon spectra of the high-symmetry phase of these compounds. The condensation of unstable modes leads to a stable polar phase P2(1). The spontaneous polarization in this phase is found to be 30 mu C/cm(2). The magnetic ground state is antiferromagnetic with an antiparallel direction of the magnetic moments in adjacent planes along the [001] direction. The N,el temperatures are estimated in the mean field approximation. The presence of the ferroelectric and magnetic order parameters in the structure suggests that the studied double perovskites with the simultaneous ordering of the cations are potential multiferroics.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : An impurity resistivity of doped manganese perovskites
Место публикации : Physica B: ELSEVIER SCIENCE BV, 1999. - Vol. 259-61: International Conference on Strongly Correlated Electron Systems (SCES 98) (JUL 15-18, 1998, PARIS, FRANCE). - P828-830. - ISSN 0921-4526, DOI 10.1016/S0921-4526(98)00875-8
Примечания : Cited References: 4
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): manganese perovskites--mobility--linear and quadratic magnetoresistance
Аннотация: We present a two-time of relaxation approach at an analysis of a magnetoresistance in ferromagnetic manganese perovskites La(1-x)(Ca,Sr)(x)MnO. To explain a change in the low-held response from predominantly quadratic dR/dH\(H--0) = 0 for T T(c) to linear dR/dH\(H--0) for T T(c) as noted in the measurements in thin films La(0.7)Ca(0.3)MnO(3) we calculated held and temperature dependences of a impurity contribution to a carrier mobility in a framework of the 2p(O)- and 3d(Mn)-scattering model elaborated for manganese perovskites. We obtained the field-dependent impurity contribution to the overall scattering of carriers that show a transition in the low-field (H) dependence of R from quadratic above T(c) to linear below consistent with an experiment. The calculated negative magnetoresistance ratio is sharply peaked at a temperature-near T(c) or below. (C) 1999 Elsevier Science B.V. All rights reserved.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Beznosikov B. V.
Заглавие : Architecture and properties of perovskite-like crystals
Коллективы : USA-CIS-Baltic Seminar on Ferroelectricity
Место публикации : Ferroelectrics: Gordon Breach Sci Publ Ltd, 1999. - Vol. 226, Is. 1-4. - P.1-9. - ISSN 0015-0193, DOI 10.1080/00150199908230285
Примечания : Cited References: 9
Ключевые слова (''Своб.индексиров.''): perovskites--perovskite-like crystals--new representatives of ruddlesden-popper's phases--new representatives of ruddlesden-popper's phases--perovskite-like crystals--perovskites
Аннотация: A variety of the known structures of perovskite-like crystals including cation- and anion-deficient phases were considered as the intergrowth systems of slabs containing n-layers (n = 1,2, 3,...infinity) of corner-linked octahedra BX6, pyramids EX5 or square-planar nets BX4 (B-cation, X- anion) linked by intermediate blocks of different types.([1- 3]) Some new structural types and new representatives of ferroelectrics, ferroelastics and HTSC's can be constructed on this basis. The prognosis of new possible representatives in Ruddlesden-Popper's family is discussed.A variety of the known structures of perovskite-like crystals including cation- and anion-deficient phases were considered as the intergrowth systems of slabs containing n-layers (n = 1, 2, 3, . . . ?) of corner-linked octahedra BX6, pyramids BX5 or square-planar nets BX4 (B-cation, X-anion) linked by intermediate blocks of different types.[1-3] Some new structural types and new representatives of ferroelectrics, ferroelastics and HTSC's can be constructed on this basis. The prognosis of new possible representatives in Ruddlesden-Popper's family is discussed.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Melnikova S. V., Anistratov A. T., Aleksandrov K. S.
Заглавие : Birefringes and structure phase-transitions in ABCl3 perovskites
Место публикации : Fiz. Tverd. Tela: Mezhdunarodnaya kniga, 1981. - Vol. 23, Is. 1. - P.246-250. - ISSN 0367-3294
Примечания : Cited References: 16
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhou, Jun, Li, Mingze, Ning, Lixin, Zhang, Ruiling, Molokeev M. S., Zhao, Jing, Yang, Songqiu, Han, Keli, Xia, Zhiguo
Заглавие : Broad-Band Emission in a Zero-Dimensional Hybrid Organic [PbBr6] Trimer with Intrinsic Vacancies
Место публикации : J. Phys. Chem. Lett. - 2019. - Vol. 10, Is. 6. - P.1337-1341. - ISSN 1948-7185, DOI 10.1021/acs.jpclett.9b00238
Примечания : Cited References: 28. - This work was supported by the National Natural Science Foundation of China (Grant Nos. 51722202, 91622125, 51572023, 11574003, 21833009, and 21533010) and the Natural Science Foundation of Beijing (2172036). We were grateful to Prof. Keli Han for his support to supply the femtosecond transient absorption spectroscopy device.
Предметные рубрики: WHITE-LIGHT EMISSION
HALIDE PEROVSKITES
LUMINESCENCE
Аннотация: The understanding of broad-band emission mechanisms on low-dimensional metal halides is an urgent need for the design principle of these materials and their photoluminescence tuning. Herein, a new zero-dimensional (0D) organic–inorganic hybrid material (C9NH20)6Pb3Br12 has been discovered, in which face-sharing PbBr6 trimer clusters crystallize with organic cations (C9NH20+), forming periodic structure with 0D blocks. Broad-band green emission peaking at about 522 nm was observed for this material, with a full width at half-maximum (fwhm) of 134 nm. The emission was attributed to excitons trapped at controlled intrinsic vacancies, and this is the new example in 0D metal halides, also confirmed by spectroscopy analysis and first-principles calculations. Discovery of the single-crystalline hybrid material and observation of defect-induced luminescence extend the scope of bulk 0D materials and understanding of photophysical properties for optoelectronic applications.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Deng, Chenkai, Hao, Shiqiang, Liu, Kunjie, Molokeev M. S., Wolverton, Christopher, Fan, Liubing, Zhou, Guojun, Chen, D.a., Zhao, Jing, Liu, Quanlin
Заглавие : Broadband light emitting zero-dimensional antimony and bismuth-based hybrid halides with diverse structures
Коллективы : Beijing Municipal Natural Science FoundationBeijing Natural Science Foundation [2182080]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51972021, 51702329]; Fundamental Research Funds for the Central UniversitiesFundamental Research Funds for the Central Universities [FRF-IDRY-19-005]; RFBRRussian Foundation for Basic Research (RFBR) [19-52-80003]; Department of Energy, Office of Science Basic Energy SciencesUnited States Department of Energy (DOE) [DE-SC0014520]
Место публикации : J. Mater. Chem. C. - 2021. - Vol. 9, Is. 44. - P.15942-15948. - ISSN 2050-7526, DOI 10.1039/d1tc04198c. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 52. - This work was supported by Beijing Municipal Natural Science Foundation (2182080) and the National Natural Science Foundation of China (51972021 and 51702329). The work was partly supported by the Fundamental Research Funds for the Central Universities (FRF-IDRY-19-005) and by the RFBR according to the research project No. 19-52-80003. S. H. and C. W. (DFT calculations) acknowledge support from the Department of Energy, Office of Science Basic Energy Sciences under Grant DE-SC0014520. Access to QUEST, the supercomputing resources facilities at Northwestern University, is also acknowledged
Предметные рубрики: CRYSTAL-STRUCTURE
LONE-PAIR
EMISSION
PEROVSKITES
TIN
LUMINESCENCE
Аннотация: Low-dimensional organic–inorganic metal halides have recently attracted extensive attention because of their various structures and distinguished photoelectric properties. Herein, we report a series of new zero-dimensional organic–inorganic hybrid metal halides: (TMEDA)3Bi2Cl12·H2O, (TMEDA)3Bi2Br12·H2O, (TMEDA)3Sb2Br12·H2O, and (TMEDA)5Sb6Cl28·2H2O [TMEDA = N,N,N′·trimethylethylenediamine]. (TMEDA)3M2X12·H2O (M = Bi or Sb, X = Cl or Br) crystallizes in the monoclinic space group P21/n, and (TMEDA)5Sb6Cl28·2H2O crystallizes in the orthorhombic space group Pnma. (TMEDA)3M2X12 possesses a zero-dimensional structure with the metal halide ions of [MBr6]3− isolated by the organic TMEDA2+ cations. Interestingly, the (TMEDA)5Sb6Cl28·2H2O structure consists of a combination of corner-connected octahedra [Sb4Cl18]6− and edge-shared [Sb2Cl10]4−, which is quite rare. The light emission of all these compounds was measured, and (TMEDA)3Sb2Br12·H2O exhibits the most intense luminescence. Upon 400 nm ultraviolet light excitation, (TMEDA)3Sb2Br12·H2O exhibited strong broadband yellow emission centered at 625 nm with a full-width at half-maximum of ∼150 nm originating from self-trapped excitons. This work suggests the possibility of new types of hybrid halides by introducing different metal centers and probing the structural evolution and photoluminescent properties, serving as a reference for the relationship between structure and luminescent performance and demonstrating their potential use as phosphors in light-emitting diodes.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Andryushin N. D., Zinenko V. I., Pavlovskii M. S., Shinkorenko A. S.
Заглавие : Calculation and Comparison of Electronic, Vibrational, Polarization, and Magnetic Properties of Double Perovskites CaMnTi2O6 and CaFeTi2O6
Место публикации : J. Exp. Theor. Phys. - 2019. - Vol. 129, Is. 6. - P.1036-1044. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776119110013
Примечания : Cited References: 18. - This work was supported by the Russian Foundation for Basic Research (project no. 18-02-00130-a)
Аннотация: Vibrational, polarization, magnetic, and electronic properties of double perovskites CaMnTi2O6 and CaFeTi2O6 with a rare type of “column” ordering of divalent metal cations have been calculated based on the density functional theory. Analysis of the crystal lattice dynamics for paraelectric phase P42/nmc of both compounds has revealed that ferroelectric instability exists only in CaMnTi2O6. It is found that the structure distortion of the paraphrase of CaMnTi2O6 in the eigenvector of the unstable polar mode leads to a structure with the P42/nmc space group. The calculated spontaneous polarization for the ferroelectric phase of CaMnTi2O6 is Ps = 25 μC/cm2. The spin-polarization calculations have shown that the ground state is ferromagnetic in the CaFeTi2O6 crystal and antiferromagnetic in the CaMnTi2O6 crystal. The exchange interaction constants have been calculated using the Heisenberg model and the mean field approximation; the phase transition temperature for each compound has been estimated.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mikhaleva E. A., Flerov I. N., Gorev M. V., Molokeev M. S., Cherepakhin A. V., Kartashev A. V., Mikhashenok N. V., Sablina K. A.
Заглавие : Caloric characteristics of PbTiO3 in the temperature range of the ferroelectric phase transition
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 9. - P.1832-1840. - ISSN 1063-7834, DOI 10.1134/S1063783412090181
Примечания : Cited References: 31. - This study was supported by the Russian Foundation for Basic Research (project no. 12-08-00079) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-4828.2012.2).
Предметные рубрики: SINGLE-CRYSTALS
LEAD TITANATE
DIELECTRIC PROPERTIES
SOLID-SOLUTIONS
PRESSURE
PEROVSKITES
DEPENDENCE
BEHAVIOR
HEAT
Аннотация: The heat capacity and thermal expansion of the PbTiO3 ceramic sample have been measured in the temperature range 80–970 K. The electrocaloric and barocaloric efficiencies of lead titanate in the ferroelectric phase transition range have been investigated by analyzing the experimental data in terms of the thermodynamic theory of phase transitions, the electrical equation of state P(T, E), the Pippard equation, and the S(T, p) diagram.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ivanova N. B., Ovchinnikov S. G., Balaev A. D., Aminov T. G., Shabunina G. G., Chernov V. K., Petukhov M. V.
Заглавие : Comparison of negative magnetoresistance mechanisms in manganese perovskites and chromium spinels
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1999. - Vol. 41, Is. 10. - P1652-1655. - ISSN 1063-7834, DOI 10.1134/1.1131064
Примечания : Cited References: 17
Предметные рубрики: ANISOTROPIC MAGNETORESISTANCE
TRANSPORT-PROPERTIES
THIN-FILMS
ALLOYS
Аннотация: A transition of the field dependence of the electrical resistivity from a square law (similar to H-2) above T-c to a linear function (similar to H) below T-c is observed in the degenerate ferromagnetic semiconductor HgCr2Se4(n). Together with the large negative magnetoresistance, these magnetoelectric effects correspond to effects observed in the perovskite-type oxides La1-xCaxMnOdelta. Inasmuch as the undoped semiconductor HgCr2Se4 is a ferromagnet with approximately the same critical temperature as the doped semiconductor and in view of the total lack of data on the Jahn-Teller effect in this compound, we infer that our results cast doubt on existing hypotheses (polaron and binary exchange) regarding the origin of the giant magnetoresistance in La1-xCaxMnOdelta. Impurity sd scattering is discussed as a possible magnetoresistance mechanism for both compounds. (C) 1999 American Institute of Physics. [S1063-7834(99)01710-4].
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sandler Yu. M.
Заглавие : Critical-behavior and elastic nonlinearity of perovskites at non-ferroelectric structure phase-transitions
Место публикации : Fiz. Tverd. Tela. - 1980. - Vol. 22, Is. 9. - P.2578-2587. - ISSN 0367-3294
Примечания : Cited References: 27
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12.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Dudnikov V. A., Platunov M. S., Orlov Yu. S., Kazak N. V., Solov’ev L. A., Zubavichus Y. V., Veligzhanin A. A., Dorovatovskii P. V., Vereshchagin S. N., Shaikhutdinov K. A., Ovchinnikov S. G.
Заглавие : Crystal structure and electronic statesof the Co and Gd ions in the single crystal Gd0.4Sr0.6CoO2.85
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : VI Euro-Asian Symposium "Trends in MAGnetism" (EASTMAG-2016): abstracts/ ed.: O. A. Maksimova, R. D. Ivantsov. - Krasnoyarsk: KIP RAS SB, 2016. - Ст.P3.12. - P.194. - ISBN 978-5-904603-06-9 (Шифр -478014040)
Примечания : References: 2. - This work was supported by Russian Science Foundation (Project 16-13-00060)
Ключевые слова (''Своб.индексиров.''): gd1-xsrxcoo3-δ perovskites--x-ray absorption spectroscopy--valence state--electronic structure
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Zinenko V. I.
Заглавие : Effect of an Eu3+ impurity on the antiferrodistortion and ferroelectric instabilities in an EuTiO3 bulk crystal and thin films
Коллективы : Russian Foundation for Basic Research [12-02-00025-a], Russian Federation [NSh-924.2014.2]
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 120, Is. 1. - P.103-109. - ISSN 1063, DOI 10.1134/S1063776115010070. - ISSN 10906509(eISSN)
Примечания : Cited References:21. - This work was supported by the Russian Foundation for Basic Research (project no. 12-02-00025-a) and the program Leading Scientific Schools of the President of the Russian Federation (project no. NSh-924.2014.2).
Предметные рубрики: PEROVSKITES
Аннотация: The existence of an antiferrodistortion transition in EuTiO3 is disputable, and this question needs to be answered. One of the possible causes is the presence of an Eu3+ impurity in a sample. A nonempirical polarizable ion model is used to study the effect of a trivalent Eu3+ ion impurity on the antiferrodistortion and ferroelectric instabilities of an EuTiO3 crystal in the bulk and the thin-film states. Lattice dynamics calculation shows that a bulk impurity-free EuTiO3 crystal has no unstable modes throughout the entire phase space volume. The addition of an Eu3+ impurity leads to a significant softening of the rotational mode, the distortion in which makes tetragonal phase I4/mcm (which is experimentally observed) energetically favorable. In going from the bulk crystal to the thin film, the vibration spectrum of the impurity-free film has unstable antiferrodistortion and rotational modes. The addition of an Eu3+ impurity enhances the antiferrodistortion instability, which fully or partly suppresses ferroelectricity.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Effect of bond fluctuations on the transport properties of manganites and nickelates
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 104, Is. 5. - P766-774. - ISSN 1063-7761, DOI 10.1134/S1063776107050111
Примечания : Cited References: 26
Предметные рубрики: NEUTRON-DIFFRACTION
CHARGE DISPROPORTIONATION
ELECTRONIC-STRUCTURE
MAGNETIC ORDER
TRANSITIONS
PEROVSKITES
PRNIO3
GAP
Ключевые слова (''Своб.индексиров.''): crystal structure--manganites--optimization--thermal conductivity--thermal effects--bond fluctuations--nickelates--orthorhombic crystal structure--nickel compounds
Аннотация: For the manganites RMnO(3) (R = La, Pr, Nd), a mechanism is proposed to explain the anomalous temperature dependences of the kinetic coefficients, resistivity, and thermoelectric power during the transition from the pseudocubic O to the orthorhombic O' crystal structure. The contributions of the bending and stretching modes of the octahedron to the formation of thermal-conductivity maxima and to the deviation from the linear dependence of ln(rho/T) on 1/T at low temperatures have been estimated. In nickelates, the metal-insulator transition is caused by lattice-polaron pinning by the stretching mode of the octahedron, and the low-temperature anomaly of the thermal conductivity is related to electron scattering by the bending mode of the octahedron.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V.
Заглавие : Entropy and the mechanism of phase transitions in elpasolites
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2001. - Vol. 43, Is. 1. - P127-136. - ISSN 1063-7834, DOI 10.1134/1.1340198
Примечания : Cited References: 33
Предметные рубрики: ORDERED PEROVSKITE PB2MGTEO6
ELASTIC NEUTRON-DIFFRACTION
THERMODYNAMIC PROPERTIES
CUBIC PEROVSKITES
CRYSTAL-STRUCTURE
HIGH-RESOLUTION
PB2MGWO6
CSPBCL3
Аннотация: The phase transitions in series of crystals with the general formulas A(2)BB'X-6 (X = F, Cl, Br, or CN) and Pb2BB'O-6 that belong to the elpasolite family (space group Fm(3) over bar m) are analyzed. The influence of the size and the shape of cations and anions on the entropy and the mechanism of structural distortions is discussed. (C) 2001 MAIK "Nauka/Interperiodica".
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16.

Вид документа : Однотомное издание
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Molokeev M. S., Laptash N. M.
Заглавие : Ferroelastic and ferroelectric phase transitions in fluoro- and oxyfluorometallates
Место публикации : Photonic and electronic properties of fluoride materials: Elsevier, 2016. - Chapter 16. - P.355-381. - (Progress in fluorine science series). - , DOI 10.1016/B978-0-12-801639-8.00016-7
Примечания : Cited References: 92. - The reported study was partially supported by RFBR, research project No. 15-02-02009 a
Предметные рубрики: ELASTIC NEUTRON-DIFFRACTION
ORIENTATIONAL DISORDER
CRYSTAL-STRUCTURES
THERMODYNAMIC PROPERTIES
NONCRITICAL PARAMETERS
CUBIC PEROVSKITES
RAMAN-SCATTERING
SINGLE-CRYSTALS
A2BX4 STRUCTURE
HIGH-RESOLUTION
Аннотация: Different degree of structural disorder is one of the main features of many fluoro- and oxyfluorometallates crystallizing in high symmetry structures. The comprehensive study of these compounds (perovskites, elpasolites, pyrochlores, etc.) enabled to determine a great effect of the size and shape as well as crystallographic sites of cationic and anionic species on the mechanism of structural ordering. Ferroelastic and ferroelectric phase transitions of different order, type, and succession can be realized as a result of chemical and hydrostatic pressure change. It was found that the substitution of monoatomic cations for tetrahedral ammonium group was accompanied by rather significant change of electron density distribution, entropy, and phase diagrams. Some compounds studied were considered to be promising solid-state refrigerants owing to the pronounced barocaloric effect resulting from large entropy and baric coefficient of phase transitions.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Aleksandrov K. S., Tressaud A., Fokina V. D.
Заглавие : Ferroelastic phase transitions in fluorides with cryolite and elpasolite structures
Место публикации : Crystallogr. Rep. - 2004. - Vol. 49, Is. 1. - P.100-107. - ISSN 1063-7745, DOI 10.1134/1.1643969
Примечания : Cited References: 43
Предметные рубрики: NUCLEAR MAGNETIC-RESONANCE
THERMODYNAMIC PROPERTIES
RB2KMIIIF6 ELPASOLITES
NEUTRON-DIFFRACTION
CRYSTALS
PEROVSKITES
DIAGRAM
SC
RB2KGAXSC1-XF6
SCATTERING
Аннотация: The ferroelastic phase transitions are investigated in several series of fluoride crystals belonging to the elpasolite and cryolite families (space group Fm (3) over barm) with the general formula A(2)BB'F-6. The influence of the size and shape of cations and anions on the entropy and the mechanism of structural distortions is discussed. (C) 2004 MAIK "Nauka/Interperiodica".
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G., Zhandun V. S., Pavlovskii M. S.
Заглавие : Ferroelectric and structural instability in double perovskites Me1+Bi3+Me3+Nb5+O6 (Me1+ = Na, K, Rb; Me3+ = Sc, Ga, In, Lu)
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 6. - P.955-962. - ISSN 1063-7761, DOI 10.1134/S1063776112040188
Примечания : Cited References: 7. - This work was supported by the Russian Foundation for Basic Research (project no. 09-02-00067) and by the program for the support of leading scientific schools (project no. NSh-4645.2010.2).
Аннотация: Within the Gordon-Kim generalized model with regard to the polarizabilities of ions, the lattice constants, the high-frequency permittivity, the Born dynamic charges, and the vibration constants of the crystal lattice are calculated for cation-ordered double perovskites Me1+Bi3+Me3+Nb5+O6. The vibration spectra of all the compounds exhibit two types of instabilities: instability associated with the rotation of the oxygen octahedron and ferroelectric instability. Various combinations of distortions with respect to the rotation mode yield five energetically most favorable distorted phases. The symmetry and the energy characteristics of these phases are discussed. In four of the five phases, the distortions associated with the oxygen octahedron rotation lead to polar phases, thus allowing one to speak of improper ferroelectricity in these compounds. One phase turns out to be nonpolar; however, it contains unstable polar modes such that a displacement along the eigenvectors of these modes gives rise to polarization in the crystal.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Troyanchuk I. O., Bushinsky M. V., Tereshko N. V., Lanovsky R. A., Sikolenko V. V., Ritter C., Orlov Yu. S., Ovchinnikov S. G.
Заглавие : Ferromagnet-antiferromagnet transition in layered perovskites of Sr3YCo4O10.5 type
Коллективы : Belarussian Foundation for Basic Research [F18R-159]; Russian Foundation Basic Research [18-52-00017 Bel_a, 16-02-00507, 18-52-00020]; Council on grants of the President of the Russian Federation [SP-1844.2016.1]
Место публикации : Mater. Res. Express. - 2019. - Vol. 6, Is. 2. - Ст.026105. - ISSN 2053-1591, DOI 10.1088/2053-1591/aaef21
Примечания : Cited References: 30. - This work was supported by the Belarussian Foundation for Basic Research (project F18R-159) and Russian Foundation Basic Research (contract no. 18-52-00020). Yu S Orlov and SG Ovchinnikov are grateful Russian Foundation Basic Research (contracts no. 18-52-00017 Bel_a, 16-02-00507) and Council on grants of the President of the Russian Federation (SP-1844.2016.1) for the support.
Предметные рубрики: SPIN
NANOWIRES
Ключевые слова (''Своб.индексиров.''): neutron diffraction--orbital ordering--spin state
Аннотация: Sr1−xYxCoO2.65 (x = 0.2) with layered perovskite structure was studied by neutron diffraction, synchrotron x-ray and magnetometry methods. It is shown that in the 90–375 K temperature range the crystal structure can be described by the monoclinic space group A2/m with the superstructure 4√2a p × 2√2a p × 4a p (with a p corresponding to the unit cell parameter of the primitive cell) while basic diffraction peaks are well indexed in the space group I4/mmm (2a p × 2a p × 4a p ) shows an almost standard magnetization. The basic magnetic structure is G-type antiferromagnetic with average magnetic moments of 2.7 μ B/Co and 1.7 μ B/Co in anion-deficient CoO4+γ and stoichiometric CoO6 layers, respectively. A ferromagnetic component of about 0.27 μ B/Co is determined from the magnetization measurements at 8 K. Sr0.8Y0.2CoO2.65 shows an almost standard magnetization versus temperature dependence whereas Sr0.75Y0.25CoO2.65 exhibits an antiferromagnet-ferromagnet transition accompanied by a structural transformation. There is practically no spontaneous magnetization in x = 0.3. The type of the magnetic structure and the high value of TN suggest that the Co3+ ions are in both structural layers predominantly in the low-spin (LS)/high-spin (HS) state mixture. It is proposed that the ferromagnetic component is due to the orbital ordering occurring at TN in the CoO5 pyramids and the concomitant appearance of ferromagnetic coupling between the Co3+(HS) ions located in these CoO5 pyramids in the anion-deficient CoO4+γ layer.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zinenko V. I.
Заглавие : First principles investigation of the magnetic, magnetoelectric, and optical properties of double perovskites containing ions of transition metals LaPbTSbO6 (T = Fe, Co, Ni)
Коллективы : Russian Foundation for Basic Research [15-02-00340]; Government of Krasnoyarsk Krai and Krasnoyarsk Krai Fund for the Support of Research and Development [16-42-243035]
Место публикации : J. Exp. Theor. Phys. - 2017. - Vol. 125, Is. 6. - P.1116-1126. - ISSN 1063-7761, DOI 10.1134/S106377611712010X. - ISSN 1090-6509(eISSN)
Примечания : Cited References:22. - This work was supported by the Russian Foundation for Basic Research, project no. 15-02-00340, and by the Government of Krasnoyarsk Krai and Krasnoyarsk Krai Fund for the Support of Research and Development (project no. 16-42-243035). The calculations were carried out on the computing facilities of the National Research Center Kurchatov Institute (ui2.computing.kiae.ru).
Аннотация: Within the first principles approach implemented in the VASP package, a correlation between magnetic, electronic, polarization, and optical properties, on the one hand, and the structural ordering of cations, on the other hand, is investigated in double perovskites LaPbTSbO6 (T = Fe, Co, Ni). Two types of cation ordering are considered: simultaneous layered (LL) and checkerboard (RR) ordering of both cations. These two types of ordering are chosen due to their significance; namely, the ordering RR is one of the most implementable types of cation ordering in double perovskites, and compounds with layered ordering can be considered as a heterostructure consisting of periodically alternating metal-nonmagnetic metal layers, which is of interest for experimental synthesis and investigation. It is found that the type of cation ordering in compounds with T = Fe and Ni radically changes the magnetic and/or electronic properties of the compound. Moreover, it is found that low-symmetry stable phases are polar for both types of cation ordering, and the values of spontaneous polarization are evaluated.
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