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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Каган, Максим Юрьевич, Вальков, Валерий Владимирович, Мицкан, Виталий Александрович, Коровушкин, Максим Михайлович
Заглавие : Механизм Кона-Латтинжера и фазовая диаграмма сверхпроводящего состояния в модели Шубина-Вонсовского
Место публикации : Журн. эксперим. и теор. физ. - 2013. - Т. 144, Вып. 4. - С. 837-852
Аннотация: В рамках модели Шубина - Вонсовского для режима слабой связи WUV (W - ширина зоны, U - хаббардовское отталкивание на узле, V - кулоновское взаимодействие на соседних узлах) на основе механизма Кона - Латтинжера определены области реализации сверхпроводящих фаз с dxy-, p-, s- и dx2-y2-типами симметрии параметра порядка. Показано, что для эффективного взаимодействия в куперовском канале существенную роль играют не только одноузельные, но и межузельные кулоновские корреляции. Этот факт продемонстрирован на примере качественного изменения и усложнения фазовой диаграммы сверхпроводящего состояния. Вскрыт механизм индуцирования сверхпроводящей фазы при учете поляризационных вкладов во втором порядке теории возмущений по кулоновскому взаимодействию. Проведено сравнение полученных результатов по угловой зависимости сверхпроводящей щели в различных каналах с экспериментальными данными по фотоэмиссии с угловым разрешением (ARPES). Проанализировано влияние дальних перескоков на фазовую диаграмму и критическую температуру сверхпроводящего перехода в различных каналах. Определены условия возникновения сверхпроводимости Кона - Латтинжера с dx2-y2-типом симметрии и высокими значениями критической температуры Tc ~ 100 K вблизи половинного заполнения.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Valkov V. V., Valkova T. A.
Заглавие : Application of indefinite metric for transition to bose description of Su(3) hamiltonians - excitation spectrum of spin nematics
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz. - 1991. - Vol. 99, Is. 6. - P.1881-1897. - ISSN 0044-4510
Примечания : Cited References: 37
Предметные рубрики: BIQUADRATIC EXCHANGE
PHASE-TRANSITIONS
DIAGRAM TECHNIQUE
MAGNETISM
FIELD
STATE
Аннотация: A procedure is developed for a correct transition to the Bose representation for quantum SU(3) Hamiltonians. The analysis is carried out for a spin nematic by applying the indefinite metric formalism and pseudo-Hubbard operators. An important aspect of the theory is that the finiteness of the number of physical states is taken into account. This is attained by introducing and consistently taking into account the metric operator for which purpose a simple expression in terms of Bose operators is suggested. It is shown that in this approach the quantum Bose analog of the Hamiltonian is an Hermitian operator. This circumstance removes a number of principle contradictions which appeared previously on application of the Bose analog of the Hamiltonian derived by virtually identifying the Hubbard and pseudo-Hubbard operators and ignoring the finiteness of the number of physical states. The integral equations defining the chief characteristics of the system are obtained and solved analytically for the spin-nematic state of a magnet with S = 1 and by taking into account anharmonic effects. This permits one to write down in nonlinear theory explicit expressions for the two branches of the quantum excitation spectrum. The character of the renormalization of the spectrum parameters due to the presence of zero-point quantum oscillations is studied. The renormalization of the critical field on transition of the system from the spin nematic state is calculated analytically.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kova T. A., Val'kov V. V.
Заглавие : Modifying the spin diagram technique for describing quantum magnets with strong fluctuations
Коллективы : International Interdisciplinary Symposium “Ordering in Minerals and Alloys” (14th; 8 -13 Sept. 2011; Rostov-on-Don)
Место публикации : Bull. Russ. Acad. Sci.: Phys.: Allerton Press, 2012. - Vol. 76, Is. 7. - P.768-770. - ISSN 1062-8738, DOI 10.3103/S1062873812070374
Примечания : Cited References: 7. - This work was supported by the Quantum Physics of Condensed Matter Program for Basic Research of the Presidium of the Russian Academy of Sciences; and by the federal target program Scientists and Science Teachers of an Innovative Russia, 2009–2013.
Ключевые слова (''Своб.индексиров.''): elementary excitations--first-order--mass operator--quantum magnets--self-consistent field method--spin operators--magnets--spin fluctuations
Аннотация: Using the diagram technique for spin operators, the exact representations for quantum magnets are obtained that express the Green's functions via the components of mass operator ∑αβ, end factors L and Q, and the Larkin-and Dyson-irreducible part T- irr.The elementary excitation spectrum and mean magnetization are calculated accurate to the first-order contributions on the parameter r0 -3 by the self-consistent field method.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Manifestation of spin-charge fluctuations in the spectral and thermodynamic properties of quasi-two-dimensional rare-earth intermetallic compounds
Коллективы : RFBR [16-02-00073-a, 15-42-04372-r-Siberia-a]; Government of the Krasnoyarsk Region; Regional Science Foundation [07/16]; Integrated program II.2P of SB RAS [0358-2015-0002]; Presidential scholarships for young PhDs [SP-1370.2015.5]
Место публикации : Low Temp. Phys.: American Institute of Physics, 2017. - Vol. 43, Is. 2. - P.191-199. - ISSN 1063-777X, DOI 10.1063/1.4977211. - ISSN 1090-6517(eISSN)
Примечания : Cited References:35. - This work was supported by RFBR (Grants Nos. 16-02-00073-a and 15-42-04372-r-Siberia-a), the Government of the Krasnoyarsk Region and the Regional Science Foundation (Ext. Agreement No. 07/16), as well as the Integrated program II.2P of SB RAS (Project No. 0358-2015-0002). One of the authors (A.O.Z.) acknowledges the support by the Presidential scholarships for young PhDs (SP-1370.2015.5).
Предметные рубрики: PERIODIC ANDERSON MODEL
INTERMEDIATE-VALENCE COMPOUNDS
MAGNETIC PHASE-DIAGRAM
HEAVY
SUSCEPTIBILITY
APPROXIMATION
ANTIFERROMAGNETISM
SUPERCONDUCTIVITY
LATTICE
METALS
Аннотация: In the framework of the modified periodic Anderson model with exchange interaction in the subsystem of localized states, it is shown that spin-charge fluctuations in quasi-two-dimensional intermetallic compounds with rare-earth ions in the mixed valence state significantly affect both the spectrum of magnetic excitations and the conditions at which the antiferromagnetic phase is realized. The spectral characteristics of the phase were obtained by the method of the diagram technique for Hubbard operators in the one-loop approximation, which allows to account for the spincharge fluctuation contributions to the components of the mass and the force operators. The developed theory allowed to quantitatively describe the pressure dependence of the Neel temperature observed in a quasi-two-dimensional antiferromagnetic heavy-fermion intermetallic compound CeRhIn5. Published by AIP Publishing.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : Electron spectrum and heat capacity of heavy fermions in the canted phase of antiferromagnetic intermetallides
Коллективы :
Место публикации : J. Exp. Theor. Phys. - 2010. - Vol. 110, Is. 2. - P.301-318. - ISSN 1063-7761, DOI 10.1134/S1063776110020147
Примечания : Cited References: 41. - This study was supported by the program "Quantum Physics of Condensed Media" of the Presidium of the Russian Academy of Sciences, interdisciplinary integration project no. 53 of the Siberian Branch of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 07-02-00226).
Предметные рубрики: PERIODIC ANDERSON MODEL
PRESSURE-INDUCED SUPERCONDUCTIVITY
KONDO-LATTICE
FERROMAGNETISM
FLUCTUATIONS
COEXISTENCE
CERHIN5
SYSTEMS
DIAGRAM
CENISN
Ключевые слова (''Своб.индексиров.''): antiferromagnetic phase--antiferromagnetics--antiferromagnets--electron spectrum--electronic heat capacity--energy spectra--experimental data--external magnetic field--heat capacities--heavy fermion--low temperatures--magnetic sublattices--magnetic subsystems--sommerfeld constant--structural rearrangement--temperature dependence--antiferromagnetism--cerium--cerium compounds--fermions--magnetic fields--phase transitions--specific heat--spectroscopy--antiferromagnetic materials
Аннотация: The energy spectrum of heavy fermions in an external magnetic field is calculated for canted magnetic sublattices of antiferromagnetic intermetallides. This makes it possible to determine low-temperature features of electronic heat capacity of heavy-fermion antiferromagnets with the metal-type ground state taking into account the structural rearrangement of the magnetic subsystem. The calculated temperature dependences of the magnetization, heat capacity, and Sommerfeld constant in the vicinity of the point of transition to the antiferromagnetic phase correlate with experimental data obtained for heavy-fermion antiferromagnets PuGa3, Ce2Au2Cd, YbNiSi3, and PuPd5Al2.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Semenov S. V., Krasikov A. A., Knyazev Yu. V., Bayukov O. A., Yakushkin S. S., Kirillov V. L., Bukhtiyarova G. A., Martyanov O. A.
Заглавие : Unusual magnetic behavior of polymorph iron oxide ϵ-Fe2O3 nanoparticles: magnetic phase diagram and surface effects
Коллективы : Российская академия наук, Уральское отделение РАН, Институт физики металлов им. М. Н. Михеева Уральского отделения РАН, Уральский федеральный университет им. первого Президента России Б.Н. Ельцина, Российский фонд фундаментальных исследований, Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : Euro-asian symposium "Trends in magnetism" (EASTMAG-2019): Book of abstracts/ чл. конс. ком.: S. G. Ovchinnikov, N. V. Volkov [et al.] ; чл. прогр. ком. D. M. Dzebisashvili [et al.]. - 2019. - Vol. 2. - Ст.J.I2. - P.164-165. - ISBN 978-5-9500855-7-4 (Шифр В33/E12-125657784)
Примечания : Cited References: 15. - This work was supported by the Russian Science Foundation, project no. 17-12-01111
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogorel'tsev E. I., Bogdanov E. V., Molokeev M. S., Voronov V. N., Isaenko L. I., Zhurkov S. A., Laptash N. M., Gorev M. V., Flerov I. N.
Заглавие : Thermodynamic Properties and Structure of Oxyfluorides Rb(2)KMoO(3)F(3) and K(2)NaMoO(3)F(3)
Разночтения заглавия :авие SCOPUS: Thermodynamic properties and structure of oxyfluorides Rb2KMoO3F3 and K2NaMoO3F3
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 6. - P1202-1211. - ISSN 1063-7834, DOI 10.1134/S1063783411060266
Примечания : Cited References: 24. - This study was supported by the Siberian Branch of the Russian Academy of Sciences within the framework of the Interdisciplinary Integration project no. 34 SO RAN and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (project no. NSh-4645-2010.2).
Предметные рубрики: T PHASE-DIAGRAM
HEAT-CAPACITY
TRANSITIONS
(NH4)(3)MOO3F3
(NH4)(3)TIOF5
(NH4)(3)WO3F3
RB2KTIOF5
CRYSTALS
CRYOLITE
DISORDER
Аннотация: According to the results of calorimetric and structural studies, the Fm (3) over barm phase in K(2)NaMoO(3)F(3) remains stable at least to 100 K. No ferroelectric transformation assumed earlier has been revealed in a series of Rb(2)KMoO(3)F(3) samples prepared using various technologies. Only a phase transition of nonferroelectric origin has been observed near 195 K, and its thermodynamic characteristics have been determined. An analysis of the stability of the cubic structure of molybdenum fluorine-oxygen elpasolites-cryolites has been performed in the framework of the hypothesis on strengths of interatomic bonds. The barocaloric effect in Rb(2)KMoO(3)F(3) has been estimated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mikhaleva E. A., Flerov I. N., Kartashev A. V., Gorev M. V., Bogdanov E. V., Bondarev V. S.
Заглавие : Thermal, dielectric and barocaloric properties of NH4HSO4 crystallized from an aqueous solution and the melt
Место публикации : Solid State Sci.: Elsevier, 2017. - Vol. 67. - P.1-7. - ISSN 12932558 (ISSN), DOI 10.1016/j.solidstatesciences.2017.03.004
Примечания : Cited References: 27. - We are grateful to T.N. Davydova for the preparation of the sample from an aqueous solution and Dr. M.S. Molokeev for X-ray characterization of the samples. The study was partially supported by the Russian Foundation for Basic Research, research project No. 16-32-00092 mol_а.
Ключевые слова (''Своб.индексиров.''): entropy--ferroelectric--phase diagram--phase transition--thermal and dielectric properties
Аннотация: A study of heat capacity, thermal dilatation, permittivity, dielectric loops and susceptibility to hydrostatic pressure was carried out on quasi-ceramic samples of NH4HSO4 obtained from an aqueous solution as well as the melt. The main parameters of the successive P21/c (T1) ↔ Pc (T2) ↔ P1 phase transitions did not depend on the method of preparation of the samples, and were close to those determined in previous studies of single crystal and powder, except for the sign and magnitude of the baric coefficient for T2. Direct measurements of the pressure effect on the permittivity and thermal properties showed dT2/dp = −123 K·GPa−1, which is consistent in terms of magnitude and sign with the baric coefficient evaluated using dilatometric and calorimetric data in the framework of the Clausius-Clapeyron equation. Thus, the temperature region of the ferroelectric Pc phase existence is extended under pressure. A strong decrease in the entropy jump at the Pc ↔ P1 transformation with an increase in pressure, and the linear dependence of T2 on pressure, indicate that an increase in pressure shifts this phase transition towards the tricritical point on the T–p phase diagram. A significant barocaloric effect was found in the region of the Pc ↔ P1 phase transition.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogoreltsev E. I., Bogdanov E. V., Kartashev A. V., Molokeev M. S., Flerov I. N., Laptash N. M.
Заглавие : Thermal properties of (NH4)2MeF6·NH4F (Me: Ti, Sn) crystals undergoing transformation between two cubic phases
Место публикации : Ferroelectrics: Taylor and Francis, 2016. - Vol. 501, Is. 1. - P.20-25. - ISSN 00150193 (ISSN), DOI 10.1080/00150193.2016.1198659
Примечания : Cited References: 9. - The reported study was partially supported by RFBR, research project No 15-02-02009-a
Ключевые слова (''Своб.индексиров.''): phase transitions--fluorides--heat capacity--entropy--phase diagram
Аннотация: The heat capacity, thermal expansion, and T-p phase diagrams of (NH4)3TiF7 and (NH4)3SnF7 were studied in wide temperature and pressure ranges. The total excess entropies at successive Pa-3 ↔ P4/mnc ↔ 4/m (Ti) and single Pa-3 ↔ Pm-3m (Sn) phase transitions are close to each other and characteristic for the order–disorder processes. The Pm-3m cubic phase and direct Pa-3 ↔ Pm-3m transformation were found at high pressure in (NH4)3TiF7. The different sign of baric coefficients for phase transition between two cubic phases in (NH4)3TiF7 and (NH4)3SnF7 was supposed due to nonlinear phase boundary with pressure in the latter fluoride.
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10.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Bondarev V. S., Maglione M., Simon A.
Заглавие : Thermal expansion, polarization and thase diagram of Ba1-xBi2x/3TiO3
Коллективы : Russia/CIS/Baltic/Japan Symposium on Ferroelectricity
Место публикации : Abstracts of the 10th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity. - 2010. - P.39
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Bormanis K., Molokeev M. S., Kalvane A.
Заглавие : Thermal expansion, polarization and phase diagram of (1-x)PbNi1/3Nb2/3O3
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.110. - ISBN 978-5-9651-1144-2
Примечания : Cited References:
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kawamata T., Sugawara N., Haidar S. M., Adachi T., Noji T., Kudo K., Kobayashi N., Fujii Yu., Kikuchi H., Chiba M., Petrakovskii G. A., Popov M. A., Bezmaternykh L. N., Koike Yo.
Заглавие : Thermal conductivity and magnetic phase diagram of CuB2O4
Место публикации : J. Phys. Soc. Jpn. - 2019. - Vol. 88, Is. 11. - Ст.114708. - ISSN 0031-9015 (ISSN), DOI 10.7566/JPSJ.88.114708. - ISSN 1347-4073 (eISSN)
Примечания : Cited References: 42. - This work was supported by a Grant-in-Aid for Scientific Research of the Ministry of Education, Culture Sports, Science and Technology, Japan, (Grant Number 17038002) and also by CREST of Japan Science and Technology Corporation.
Аннотация: We have measured temperature and magnetic field dependences of the thermal conductivity along the c-axis, κc, and that along the [110] direction, κ110, of CuB2O4 single crystals in zero field and magnetic fields along the c-axis and along the [110] direction. It has been found that the thermal conductivity is nearly isotropic and very large in zero field and that the thermal conductivity due to phonons is dominant in CuB2O4. The temperature and field dependences of κc and κ110 have markedly changed at phase boundaries in the magnetic phase diagram, which has been understood to be due to the change of the mean free path of phonons caused by the change of the phonon-spin scattering rate at the phase boundaries. It has been concluded that thermal conductivity measurements are very effective for detecting magnetic phase boundaries.
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ivanov Yu.N., Sukhovsky A.A., Voronov V.N., Bondarev V.S.
Заглавие : The study of phase diagram of solid solution NaNbxTa1-xO3 by calorimetrical and NMR MAS 23Na methods
Коллективы : "Functional Materials", International Conference
Место публикации : International Conference "Functional Materials" (ICFM-09): book of abstracts : October 5-10, Ukraine, Crimea, Partenit. - 2009. - С. 62
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yurev I. O., Aleksandrovsky A. S., Kamaev D. N., Polkovnikov A. A., Grigorchenko V. M., Yarovenko A. A., Zelenaya A. E., Parfenova M. D., Andreev O. V.
Заглавие : The Sm2S3-X-SmS-Sm2O2S refractory system: thermal analysis, phase diagram, and properties of the phases
Колич.характеристики :17 с
Место публикации : J. Therm. Anal. Calorim. - 2024. - Vol. 149, Is. 5. - P.2057-2073. - ISSN 13886150 (ISSN), DOI 10.1007/s10973-023-12792-z. - ISSN 15882926 (eISSN)
Примечания : Cited References: 90. - The authors thank Prof. P.P. Fedorov, Chief Researcher of Prokhorov Institute of General Physics, Russian Academy of Sciences, for scientific advices. The authors thank N.I. Lozhkin, engineer of the Department of Inorganic and Physical Chemistry, Tyumen State University for the technical support of the visual thermal analysis setup. The authors thank N.A. Shulaev, research engineer of the Center for Nature-Inspired Engineering, Tyumen State University, for determining the elemental composition of samples by scanning electron microscopy. The authors thank I.V. Palamarchuk, research engineer of the Center for Collective Use "Rational Nature Management and Physical and Chemical Research" of the Tyumen State University, for measuring the diffuse reflectance spectra. The authors thank Doctor of Philology O.V. Trofimova, Professor at the Institute of Social Sciences and Humanities of the Tyumen State University, for her advices on academic writingThis study was funded by the Russian Science Foundation, Project No. 23–23-00488 “Search for EMF generation conditions in gradient ceramics of samarium monosulfide (SmS)”
Аннотация: Samarium monosulfide, a strain gauge and barometric material, exists in equilibrium with Sm3S4 and Sm2O2S in the S-Sm–O system. Therefore, studying phase equilibria in the refractory Sm2S3-X-SmS-Sm2O2S system is a scientifically interesting task. In this system, 49 samples were synthesized and studied by powder XRD, differential scanning calorimetry, visual thermal analysis, and microstructural analysis. Melting points of Sm3S4, SmS, and Sm2O2S compounds were determined. Eutectic diagrams of Sm3S4-Sm2O2S, SmS-Sm2O2S, SmS-Sm3S4 systems were constructed. Temperatures and compositions of the binary eutectic points were determined. Fusion enthalpies for Sm3S4, SmS, and Sm2O2S phases were estimated using the Schröder–Le Chatelier equation. The liquidus lines were calculated using second-degree polynomials and Redlich–Kister model. Coordinates of the ternary eutectic point in the Sm3S4-SmS-Sm2O2S system were calculated using the cutting-plane method and the Scheffé method. The calculated compositions of ternary eutectic points were averaged at one most probable point, in accordance with the data on the samples microstructure. The experimental temperature of the ternary eutectic point coincides with the calculated values within the margin of error. Positions of eutectic valleys and approximate positions of isotherms in the system were established. Thermodynamic parameters of the α-Sm2S3 → γ-Sm2S3 polymorphic transition and the dependence of the Sm2S3-X composition on heat treatment conditions were determined. According to the scanning electron microscopy data, the approximate composition of the crystallized from the melt Sm2S3 sample is Sm2S2.95. The Sm10S14O phase decomposes at 1470 ± 15 °C in the course of a solid-phase reaction. The phase diagram of the Sm2S3-X-Sm2O2S system was revisited. Optical band gaps of Sm10S14O and Sm2O2S phases were determined. The Sm10S14O compound was optically characterized for the first time; its direct and indirect optical bandgaps were found equal to 2.48 and 2.37 eV, respectively. The determined direct and indirect optical bandgaps of Sm2O2S (4.4 eV and 3.95 eV, respectively) agree with the earlier measurements, thus confirming the accuracy of the chosen synthesis procedures.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Tressaud A., Durand E.
Заглавие : The p-T phase diagram of ammonium hexafluoroaluminate
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2002. - Vol. 14, Is. 25. - P6447-6453. - ISSN 0953-8984, DOI 10.1088/0953-8984/14/25/312
Примечания : Cited References: 17
Предметные рубрики: NUCLEAR MAGNETIC-RESONANCE
TRANSITIONS
MOTIONS
F-19
H-1
Ключевые слова (''Своб.индексиров.''): entropy--hydrostatic pressing--mathematical models--order disorder transitions--phase diagrams--specific heat of solids--ammonium hexafluoroaluminate--crolite--elpasolite--ammonium compounds
Аннотация: The heat capacity and the effect of hydrostatic pressure on structural phase transitions in ammonium hexafluoroaluminate, (NH4)(3)AlF6, have been studied. Two heat capacity anomalies have been found with maxima at T-1 = 218.5 +/- 0.5 K and T-2 = 179 +/- 2 K. Respective entropy changes of phase transitions are DeltaS(1) = 15.3 +/- 0.5 J mol(-1) K-1 and DeltaS(2) = 2.5 +/- 0.5 J mol(-1) K-1. It is shown that the p-T phase diagram of this compound is rather complex and contains a triple point (p(tp) = 0.12 GPa, T-tp = 221 K) and high-pressure phase. The mechanism of transformations and generalized p-T phase diagram for compounds of the (NH4)(3)(MF6)-F-III family are discussed within the framework of the rotational order-disorder model.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavriliuk A. G., Lyubutin I. S., Starchikov S. S., Mironovich A. A., Ovchinnikov S. G., Trojan I. A., Xiao, Yuming, Chow P., Sinogeikin S. V., Struzhkin V. V.
Заглавие : The magnetic P-T phase diagram of langasite Ba3TaFe 3Si2O14 at high hydrostatic pressures up to 38 GPa
Место публикации : Applied Physics Letters. - 2013. - Vol. 103, Is. 16. - Ст.162402. - P. - ISSN 0003-6951, DOI 10.1063/1.4822422
Аннотация: The langasite-type crystals with 3d ions are considered as a class of multiferroics in which ferroelectricity can be induced by the magnetic ordering. In this paper, the high-pressure magnetic states of the langasite-type powdered sample Ba3TaFe3Si2O14 have been investigated in a diamond anvil cell by the nuclear forward scattering of synchrotron radiation technique at different temperatures in hydrostatic conditions. In the pressure range of 0 < P < 19.5 GPa, an increase of the Neel temperature TN from 27 to 41 K was observed in the antiferromagnetic phase of the material. At pressures ?19.5 GPa, a transition to another magnetic phase with huge increase in the Neel temperature to ?120 K was found. We attribute this change to the structural transition at ?19.5 GPa which is evidenced by a drastic change of Raman spectra at this pressure. A tentative magnetic P-T phase diagram of Ba3TaFe 3Si2O14 is proposed. В© 2013 AIP Publishing LLC.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Val'kov V. V., Mitskan V. A., Korovushkin M. M.
Заглавие : The Kohn-Luttinger mechanism and phase diagram of the superconducting state in the Shubin-Vonsovsky model
Место публикации : Journal of Experimental and Theoretical Physics. - 2013. - Vol. 117, Is. 4. - P.728-741. - ISSN 1063-7761, DOI 10.1134/S1063776113120030
Аннотация: Using the Shubin-Vonsovsky model in the weak-coupling regime W > U > V (W is the bandwidth, U is the Hubbard onsite repulsion, and V is the Coulomb interaction at neighboring sites) based on the Kohn-Luttinger mechanism, we determined the regions of the existence of the superconducting phases with the d xy, p, s, and $d-{x. - y. } $ symmetry types of the order parameter. It is shown that the effective interaction in the Cooper channel considerably depends not only on single-site but also on intersite Coulomb correlations. This is demonstrated by the example of the qualitative change and complication of the phase diagram of the superconducting state. The superconducting (SC) phase induction mechanism is determined taking into account polarization contributions in the second-order perturbation theory in the Coulomb interaction. The results obtained for the angular dependence of the superconducting gap in different channels are compared with angule-resolved photoemission spectroscopy (ARPES) results. The influence of long-range hops in the phase diagram and critical superconducting transition temperature in different channels is analyzed. The conditions for the appearance of the Kohn-Luttinger superconductivity with the $d-{x. - y. } $ symmetry and high critical temperatures T c ? 100 K near the half-filling are determined. В© 2013 Pleiades Publishing, Inc.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Val'kov V. V., Mitskan V. A., Korovushkin M. M.
Заглавие : The Kohn-Luttinger effect and anomalous pairing in new superconducting systems and graphene
Коллективы : Physics Department of the Russian Academy of Sciences [P.3.1]; Russian Foundation for Basic Research [14-02-00058, 14-02-31237]; Russian Federation [MK-526.2013.2]; Dynasty Foundation
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2014. - Vol. 118, Is. 6. - P.995-1011. - ISSN 1063-7761, DOI 10.1134/S1063776114060132. - ISSN 1090-6509
Примечания : Cited References: 114. - This study was supported by the Program of the Physics Department of the Russian Academy of Sciences (project no. P.3.1) and the Russian Foundation for Basic Research (project nos. 14-02-00058 and 14-02-31237). The work of two coauthors (M. M. K. and V.A.M) was supported financially by grant no. MK-526.2013.2 of the President of the Russian Federation and the Dynasty Foundation.
Предметные рубрики: P-WAVE SUPERCONDUCTIVITY
EXTENDED HUBBARD-MODEL
NARROW ENERGY-BANDS
2D KONDO-LATTICE
FERMI GAS
REPULSIVE INTERACTIONS
ELECTRON CORRELATIONS
COOPER INSTABILITY
PHASE-DIAGRAM
SPECTRUM
Аннотация: We present a review of theoretical investigations into the Kohn-Luttinger nonphonon superconductivity mechanism in various 3D and 2D repulsive electron systems described by the Fermi-gas, Hubbard, and Shubin-Vonsovsky models. Phase diagrams of the superconducting state are considered, including regions of anomalous s-, p-, and d-wave pairing. The possibility of a strong increase in the superconducting transition temperature T c even for a low electron density is demonstrated by analyzing the spin-polarized case or the two-band situation. The Kohn-Luttinger theory explains or predicts superconductivity in various materials such as heterostructures and semimetals, superlattices and dichalcogenides, high-T c superconductors and heavy-fermion systems, layered organic superconductors, and ultracold Fermi gases in magnetic traps. This theory also describes the anomalous electron transport and peculiar polaron effects in the normal state of these systems. The theory can be useful for explaining the origin of superconductivity and orbital currents (chiral anomaly) in systems with the Dirac spectrum of electrons, including superfluid 3He-A, doped graphene, and topological superconductors.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Grossman, Victoria G., Bazarova J. G., Molokeev M. S., Bazarov B. G.
Заглавие : Thallium ionic conductivity of new thallium indium hafnium molybdate ceramics
Коллективы : RFBRRussian Foundation for Basic Research (RFBR) [0339-2016-0007]; [18-08-00799]; [18-03-00557]
Место публикации : Ionics. - 2020. - Vol. 26. - P.6157-6165. - ISSN 0947-7047, DOI 10.1007/s11581-020-03739-7. - ISSN 1862-0760(eISSN)
Примечания : Cited References: 60. - This study was carried out within the state assignment of FASO of Russia (Theme No 0339-2016-0007) as well was supported by RFBR Grants 18-08-00799 and 18-03-00557
Предметные рубрики: POSITIVE ELECTRODE MATERIAL
CRYSTAL-STRUCTURE
TRIPLE MOLYBDATE
Аннотация: In the process of studying the system Tl2MoO4–In2(MoO4)3–Hf(MoO4)2, a new thallium indium hafnium molybdate was found. The crystal structure of the molybdate Tl5InHf(MoO4)6 was determined in the centrosymmetric space group R3¯c (a = 10.63893 (5) Å, c = 38.1447(3) Å; V = 3739.04 (4) Å3, Z = 6). The structure is a three-dimensional framework consisting of alternating (Hf,In)O6-octahedra connected by МоО4-tetrahedra. Each octahedron has common vertices with tetrahedra. The atoms arranged in this way form channels extended along with the a and b axes, in which thallium atoms are located. The conductivity behavior of Tl5InHf(MoO4)6 ceramics was studied in the temperature range from 300 to 870 K. The conductivity of the heavy cations of thallium is activated with increasing temperature.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Melnikova S. V., Grankina V. A., Bandarenko G. V., Gorev M. V.
Заглавие : T-x phase diagram of solid solutions RbxK1-xLiSO4
Коллективы : International Seminar on Physics of Ferroelastics
Место публикации : Izv. Akad. Nauk Ser. Fiz. - 1998. - Vol. 62, Is. 8. - P.1537-1540. - ISSN 1026-3489
Примечания : Cited References: 4
Предметные рубрики: TRANSITIONS
CRYSTALS
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