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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov M. I., Balaev D. A., Shaikhutdinov K. A., Aleksandrov K. S.
Заглавие : A comparative study of transport properties of composites HTSC+MgTiO3 and HTSC + NiTiO3. The effect of paramagnetic NiTiO3
Коллективы : International conference on materials and mechanisms of superconductivity high temperature superconductors
Место публикации : Physica C-Superconductivity and its Applications. - 2000. - Vol. 341-348, Pt. 3. - P.1863-1864. - ISSN 0921-4534, DOI 10.1016/S0921-4534(00)01217-X
Ключевые слова (''Своб.индексиров.''): composite materials--copper oxides--josephson junction devices--magnesium compounds--nickel compounds--paramagnetism--superconductivity--thermal effects--transport properties--yttrium compounds--abrikosov vortices flow--superconductor insulator superconductor junction--thermally activated phase slippage--high temperature superconductors
Аннотация: Bulk composites Y3/4Lu1/4Ba2Cu3O7+NiTiO3 and Y3/4Lu1/4Ba2Cu3O7+MgTiO3 with insulator volume content 7.5% and 15% modelling a network of Superconductor-Insulator-Superconductor (S-I-S) junctions have been prepared. The ?(T) dependences of composites HTSC+MgTiO3 are described well by the mechanism of Thermally Activated Phase Slippage (TAPS). The anomalous behavior of resistivity ?(T) of HTSC+NiTiO3 composites manifesting as a kink on ?(T) curves at some temperature Tm have been observed. In the temperature range Tm < T < TC the dissipation is Ohmic while below Tm the CVCs are strongly non-linear. This peculiarity is interpreted as arisen owing to Abrikosov vortices flow.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Nemtsev A. V.
Заглавие : Ab initio comparative study of the magnetic, electronic and optical properties of AB2O4 (A, B= Mn, Fe) spinels
Место публикации : Mater. Chem. Phys. - 2021. - Vol. 259. - Ст.124065. - ISSN 0254-0584 (ISSN), DOI 10.1016/j.matchemphys.2020.124065. - ISSN 1879-3312 (eISSN)
Примечания : Cited References: 32. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project № 19-42-240016: «Control of structural, magnetic, electronic, and optical properties by pressure and intercalation into functional compounds with a spinel structure containing 3d and 4f ions » The calculations were performed with the computer resources of “Complex modeling and data processing research installations of mega-class” SRC “Kurchatovsky Institute” (http://ckp.urcki.ru)
Аннотация: The comparison of the magnetic, electronic, and optical properties of the spinel transition-metal oxides AB2O4 (A, B = Fe, Mn) and their relationship with the structure and composition were studied within DFT-GGA + U approximation. The spinels were considered both in the normal and inverse structure. We have found that regardless of composition and structure, the studied spinels are ferrimagnetic with antiparallel magnetic moments on A- and B-site cations. Electronic and structural properties of spinels depend on the composition: FeMn2O4 has a tetragonal structure and half-metallic properties; however, in the inverse FeMn2O4, the bandgap opens for the spin-up channel. MnFe2O4 is a cubic insulator with a bandgap of about 1.5 eV, which decreases in the inverse structure. The superexchange constants estimate within the simple indirect coupling model and have values close to the experimental ones. The total magnetization of FeMn2O4 is drop-down to zero under hydrostatic pressure above 60 GPa due to the strong dependence of the magnetic moment of octahedral manganese ion on the pressure. The microscopic mechanisms of the relationship between the structure, composition and properties are studied.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov M. I., Gokhfeld D. M., Balaev D. A., Shaihutdinov K. A., Kummel R.
Заглавие : Andreev reflections and experimental current-voltage characteristics of break junctions of polycrystalline HTSC
Место публикации : Physica C: ELSEVIER SCIENCE BV, 2004. - Vol. 408: 7th International Conference on Materials and Mechanisms of Superconductive and High Temperature Superconductors (MAY 25-30, 2003, Rio de Janeiro, BRAZIL). - P620-622. - ISSN 0921-4534, DOI 10.1016/j.physc.2004.03.085
Примечания : Cited References: 3
Ключевые слова (''Своб.индексиров.''): andreev reflections--break junction--current-voltage characteristics--andreev reflections--break junction--current-voltage characteristics--andreev reflections--break junctions--elastic scattering--lattice defects--negative differential resistance--electric fields--heuristic methods--hysteresis--microcracks--polycrystalline materials--probability density function--quasicrystals--superconducting materials--yttrium barium copper oxides--current voltage characteristics
Аннотация: The temperature evolution of current-voltage characteristics (CVCs) of break junctions made from polycrystalline Y0.75Lu0.25Ba2Cu3O7 and La1.85Sr0.15CuO4 is investigated. The experimental CVCs have hysteretic features that reflect a part of a curve with negative differential resistance. The temperature evolution of the CVCs is discussed within the framework of the Kummel-Gunsenheimer-Nicolsky theory for superconductor/normal-metal/superconductor junctions considering multiple Andreev reflections. It is shown that the shape of the CVCs of break junctions is determined by the ratio of the number of "short" and "long" intergrain normal regions in the polycrystalline HTSC under investigation. (C) 2004 Elsevier B.V. All rights reserved.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Mikhaleva E. A., Kartashev A. V., Bondarev V. S.
Заглавие : Caloric Effects in Some Ferroelectric and Ferroelastic Fluorides, Oxyfluorides and Oxides
Коллективы : Russia/CIS/Baltic/Japan Symposium on Ferroelectricity, International Workshop on Relaxor Ferroelectrics
Место публикации : Joint 13th Russia/CIS/Baltic/Japan Symp. on Ferroelectricity and Int. Workshop on Relaxor Ferroelectrics (RCBJSF-IWRF 2016): book of abstracts. - 2016. - Ст.Invite-6
Примечания : References: 4. - The reported study was partially supported by RFBR, research project No. 15-02-02009 a
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov D. A., Lin C. R., Ivantsov R. D., Ovchinnikov S. G., Zharkov S. M., Yurkin G. Yu., Velikanov D. A., Knyazev Yu. V., Molokeev M. S., Tseng Y. T., Lin E. S., Edelman I. S., Baskakov A. O., Starchikov S. S., Lyubutin I. S.
Заглавие : Characterization of the iron oxide phases formed during the synthesis of core-shell FexOy@C nanoparticles modified with Ag
Место публикации : Nanotechnology. - 2020. - Vol. 31, Is. 39. - Ст.395703. - ISSN 13616528 (ISSN), DOI 10.1088/1361-6528/ab9af2
Примечания : Cited References: 46. - The reported study was funded by Joint Research Project of Russian Foundation for Basic Research № 19-52-52002 and Ministry of Science and Technology, Taiwan MOST № 108-2923-M-153-001-MY3 and № 106-2112-M-153-001-MY3. The samples of series 1 were studied with the support of the Ministry of Science and Higher Education of the Russian Federation within the State assignment FSRC «Crystallography and Photonics» RAS. The electron microscopy investigations were conducted in the SFU Joint Scientific Center supported by the State assignment (#FSRZ-2020-0011) of the Ministry of Science and Higher Education of the Russian Federation
Аннотация: Core–shell FexOy@C nanoparticles (NPs) modified with Ag were studied with x-ray diffraction, transmission electron microscopy, energy dispersive elemental mapping, Mössbauer spectroscopy, static magnetic measurements, and optical magnetic circular dichroism (MCD). FexOy@C NPs synthesized by the pyrolysis process of the mixture of Fe(NO3)3 centerdot 9H2O with oleylamine and oleic acid were added to a heated mixture of oleylamine and AgNO3 in different concentrations. The final product was a mixture of iron oxide crystalline NPs in an amorphous carbon shell and Ag crystalline NPs. The iron oxide NPs were presented by two magnetic phases with extremely close crystal structures: Fe3O4 and γ-Fe2O3. Ag is shown to form crystalline NPs located very close to the iron oxide NPs. An assumption is made about the formation of hybrid FexOy@C-Ag NPs. Correlations were obtained between the Ag concentration in the fabricated samples, their magnetic properties and the MCD spectrum shape. Introducing Ag led to a approximately linear decrease of the NPs saturation magnetization depending upon the Ag concentration, it also resulted into the MCD spectrum shift to the lower light wave energies. MCD was also studied for the Fe3O4@C NPs synthesized earlier with the same one-step process using different heat treatment temperatures, and MCD spectra were compared for two series of NPs. A possible contribution of the surface plasmon excitation in Ag NPs to the MCD spectrum of the FexOy@C-Ag NPs is discussed.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Edelman I. S., Ivantsov R. D., Vorotynova O.V., Petrov, D. A., Seredkin V. A., Valeev V. F., Khaibullin R. I., Stepanov A.
Заглавие : Co nanoparticles in Si oxides: magnetoopical spectra
Коллективы : Moscow International Symposium on Magnetism, Московский государственный университет им. М.В. Ломоносова, Российский фонд фундаментальных исследований
Место публикации : Moscow Int. Symp. on Magnet. (MISM-2008): June 20-25, 2008, Moscow : book of abstract. - 2008. - p.310
Примечания : Библиогр.: 1. - Support of RFBR (07-02-93174, 07-03-00320) is acknowledged
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Kobyakov A. V., Yushkov V. I., Rautskii M. V., Volochaev M. N., Patrin G. S.
Заглавие : Combined method of removing the natural oxide silicon
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.P11.3. - P.535. - ISBN 978-5-904603-06-9 (Шифр -478014040)
Ключевые слова (''Своб.индексиров.''): surface--oxides--high-frequency plasma
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Comparison of electronic structure, magnetic mechanism, and symmetry of pairing in ruthenates and cuprates
Место публикации : Ruthenate and rutheno-cuprate materials: unconventional superconductivity, magnetism and quantum phase transitions. Ser. lecture notes in physics: Springer Verlag, 2002. - Vol. 603: International Conference on Ruthenate and Rutheno-Cuprate Materials (OCT 25-27, 2001, VIETRI SUL MARE, ITALY). - P.239-255. - ISBN 0075-8450. - ISBN 3-540-44275-8
Примечания : Cited References: 48
Предметные рубрики: METAL-INSULATOR-TRANSITION
SUPERCONDUCTOR SR2RUO4
LAYERED PEROVSKITE
BAND-STRUCTURE
CORRELATED ELECTRONS
MOTT TRANSITION
COPPER OXIDES
HUBBARD-MODEL
RUSR2GDCU2O8
CA2-XSRXRUO4
Аннотация: A generalized tight-binding (GTB) method is developed to calculate quasi-particle band structure with explicit account for strong electronic correlations. The GTB method combines exact diagonalization of the multi-orbital P-d model Hamiltonian within the unit cell and the perturbation theory in the Hubbard X-operators form for the inter-cell hopping and interactions. For undoped cuprates we obtain the valence band structure in excellent agreement with ARPES data, evolution of the band structure with doping with an in-gap state at small doping, impurity-like band at higher doping to optimally doped metal. The effective low-energy Hamiltonian has the form of singlet-triplet t-J model. For ruthenates the t-J-I model is proposed with both antiferromagnetic J and ferromagnetic I couplings. In the strong correlation limit, the mean-field theory of superconductivity results in d-wave singlet pairing mediated by J (cuprates) and p-wave triplet one mediated by I (ruthenates) with ratio T-c((d))/T-c((p)) similar to 100 due to the different symmetry of the gap. The competition of ferromagnetic and antiferromagnetic order in rutheno-cuprates is also discussed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min E. V., Ovchinnikov S. G., Baklanov I. O.
Заглавие : Comparison of superconductivity in Sr2RuO4 and copper oxides
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2000. - Vol. 61, Is. 22. - P15392-15397. - ISSN 1098-0121, DOI 10.1103/PhysRevB.61.15392
Примечания : Cited References: 21
Предметные рубрики: T-J MODEL
HUBBARD-MODEL
LAYERED PEROVSKITE
ELECTRONS
Аннотация: To compare the superconductivity in strongly correlated electron systems with the antiferrornagnetic fluctuations in the copper oxides and with the ferromagnetic fluctuations in Sr2RuO4 a t-J-l model is proposed. The antiferromagnetic coupling J results in the superconducting state of d(x2-y2) symmetry and the ferromagnetic coupling I results in the spin-triplet p-type state. The difference in the gap anisotropies provides the large difference in T-c values, for the typical values of the coupling constants: T-c similar to 1 K for the ruthenste and T-c similar to 100 K for the cuprates.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bataleva, Yu. V., Palyanov, Yu. N., Borzdov, Yu. M., Bayukov O. A., Sobolev N. V.
Заглавие : Conditions for diamond and graphite formation from iron carbide at the P-T parameters of lithospheric mantle
Коллективы : Russian Science Foundation [14-27-00054]
Место публикации : Russ. Geol. Geophys.: Elsevier Science, 2016. - Vol. 57, Is. 1: Tectonics, geodynamics, and petrology of earth’s lithosphere and mantle (to the 80th birthday of Academician Nikolai Leontievich Dobretsov). - P.176-189. - ISSN 1068-7971, DOI 10.1016/j.rgg.2016.01.012. - ISSN 1878-030X(eISSN)
Примечания : Cited References:55. - This work was supported by the Russian Science Foundation under Grant No. 14-27-00054.
Предметные рубрики: DEEP CARBON-CYCLE
EARTHS MANTLE
MINERAL INCLUSIONS
HIGH-PRESSURE
KOKCHETAV MASSI
SUBDUCTION ZONES
REDOX BUDGET
FERRIC IRON
MOSSBAUER
METAL
Ключевые слова (''Своб.индексиров.''): iron carbide--wusite--graphite--diamond--oxides--olivine--subduction--redox interaction--lithospheric mantle--high-pressure experiment
Аннотация: To estimate conditions for the stability of iron carbide under oxidation conditions and to assess the possibility of formation of elemental carbon by interaction between iron carbide and oxides, experimental modeling of redox interaction in the systems Fe3C-Fe2O3 and Fe3C-Fe2O3-MgO-SiO2 was carried out on a split-sphere high-pressure multianvil apparatus at 6.3 GPa and 900-1600 degrees C for 18-20 h. During carbide-oxide interaction in the system Fe3C-Fe2O3, graphite crystallizes in assemblage with Fe3+-containing wusite. Graphite forms from carbide carbon mainly by cohenite oxidation: Fe3C + 3Fe(2)O(3) - 9FeO + C-0 and FeO + Fe3C - (Fe2+, Fe3+)O + C-0. At above-solidus temperatures (= 1400 degrees C), when metal-carbon melt is oxidized by wusite, graphite and diamond crystallize by the redox mechanism and form the Fe3+-containing wstite + graphite/diamond assemblage. Interaction in the system Fe3C-Fe2O3-MgO-SiO2 results in the formation of Fe3+-containing mannesiowusite-olivine-graphite assemblage. At = 1500 degrees C, two melts with contrasting f(O2) values are generated: metal-carbon and silicate-oxide; their redox interaction leads to graphite crystallization and diamond growth. Under oxidation conditions, iron carbide is unstable in the presence of iron, silicon, and magnesium oxides, even at low temperatures. Iron carbide-oxide interaction at the mantle temperatures and pressures leads to the formation of elemental carbon; graphite is produced from carbide carbon mainly by redox reactions of cohenite (or metal-carbon melt) with Fe2O3 and FeO as well as by interaction between metal-carbon and silicate-oxide melts. The results obtained suggest that cohenite can be a potential source of carbon during graphite (diamond) formation in the lithospheric mantle and the interaction of iron carbide with iron, silicon, and magnesium oxides, during which carbon is extracted can be regarded as a process of the global carbon cycle. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Y. S., Ovchinnikov S. G.
Заглавие : Construction of a Multielectron Basis for Mott Insulators with Strong Electron Correlations, Spin-Orbit Interaction, and Covalence
Место публикации : J. Exp. Theor. Phys. - 2009. - Vol. 109, Is. 2. - P.322-338. - ISSN 1063-7761, DOI 10.1134/S1063776109080196
Примечания : Cited References: 35
Предметные рубрики: NARROW ENERGY BANDS
MAGNETIC ANISOTROPY ENERGY
ORIGIN
TRANSITION
PHYSICS
MANGANITES
OXIDES
CHARGE
Аннотация: We propose that the apparatus of quantum mechanics of a free atom (in particular, the theory of nj symbols and Rakah-Wigner genealogic coefficients generalized to the case of point groups and widely used in crystal field theory) be used for constructing multielectron bases with allowance for covalence and spin-orbit interaction. This allows us to take into account the electron-electron interaction for 3d ions the most comprehensively. The basis constructed in this way can be used in the generalized strong coupling method for the multiband p-d model in describing the structure of the quasiparticle energy spectrum and physical properties of systems with strong electron correlations. The procedure of construction and computation is demonstrated for the (5)T(2g) term in the d(6) configuration of the transition metal atom in an octahedral field. The mechanism for the emergence of magnetic anisotropy in S ions (Fe(3+) and Mn(2+)) due to covalent mixing of d(6) (L) under bar configurations with a nonzero orbital angular momentum ((L) under bar is a hole in ligands) is demonstrated
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Ovchinnikov S. G., Orlov Yu.S., Kazak N. V., Michel C. R., Patrin G. S., Yurkin G.Yu.
Заглавие : Contribution of Co3+ ions to the high-temperature magnetic and electrical properties of GdCoO3
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 5. - P.841-849. - ISSN 1063-7761, DOI 10.1134/S106377611203003X
Примечания : Cited References: 28. - This work was supported by the Ural Branch of the Russian Academy of Sciences and Siberian Branch of the Russian Academy of Sciences (project no. 40), the Russian Foundation for Basic Research (project nos. 09-02-00171-a, 10-02-00251), program 2.3 of the Department of Physical Sciences of Russian Academy of Sciences, and Nonprofit Dinastiya Foundation.
Предметные рубрики: SPIN-STATE
RCOO3 R
TRANSITIONS
COBALTITES
LACOO3
OXIDES
SM
EU
ND
Аннотация: The temperature dependence of the static magnetization of polycrystalline rare-earth cobaltite GdCoO3 is measured in the temperature range 2-800 K. The magnetic behaviors of GdCoO3 and Gd3+ are found to be different at temperatures above room temperature, which is caused by the appearance of a contribution from Co3+ ions at high temperatures. The temperature dependence of the magnetic susceptibility of GdCoO3 is determined by the magnetization of rare-earth gadolinium ions and the additional paramagnetic contribution induced by the thermally excited magnetic terms of Co3+ ions. The LDA + GTB method is used to calculate the electronic structure of GdCoO3 in the temperature range 0-300 K with allowance for strong electron correlations. The energy spectrum of GdCoO3 is found to have intragap states that decrease the dielectric gap width with increasing temperature.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Sokolov A. Е., Dudnikov V. A., Shulga K. V., Volochaev M. N., Zharkov S. M., Shestakov N. P., Vysotin M. A., Ovchinnikov S. G.
Заглавие : Contribution of the multiplicity fluctuation in the temperature dependence of phonon spectra of rare-earth cobaltites
Место публикации : Molecules. - 2020. - Vol. 25, Is. 18. - Ст.4316. - ISSN 14203049 (ISSN), DOI 10.3390/molecules25184316
Примечания : Cited References: 34. - This work was supported by the Russian Science Foundation grant 18-02-00022. The scanning electron microscopy investigations were conducted in the SFU Joint Scientific Center, supported by the State assignment (#FSRZ-2020-0011) of the Ministry of Science and Higher Education of the Russian Federation. The other research was carried out at the Krasnoyarsk Regional Center of Research Equipment of the Federal Research Center “Krasnoyarsk Science Center SB RAS”
Аннотация: We have studied, both experimentally and theoretically, the unusual temperature dependence of the phonon spectra in NdCoO3, SmCoO3 and GdCoO3, where the Co3+ ion is in the low-spin (LS) ground state, and at the finite temperature, the high-spin (HS) term has a nonzero concentration nHS due to multiplicity fluctuations. We measured the absorption spectra in polycrystalline and nanostructured samples in the temperature range 3–550 K and found a quite strong breathing mode softening that cannot be explained by standard lattice anharmonicity. We showed that the anharmonicity in the electron–phonon interaction is responsible for this red shift proportional to the nHS concentration.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shneyder E. I., Ovchinnikov S. G., Shnurenko A. V.
Заглавие : Contribution of the non-Heisenberg ring exchange to the magnetic mechanism of high-Tc superconductivity
Место публикации : JETP Letters. - 2012. - Vol. 95, Is. 4. - P.193-197. - ISSN 0021-3640, DOI 10.1134/S0021364012040078
Примечания : Cited References: 44. - This work was supported by the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (project no. NSh-1044.2012.2), by the Russian Foundation for Basic Research (project no. 12-02-00040), by the Presidium of the Russian Academy of Sciences (program no. 20 "Quantum Mesoscopic and Disordered Systems"), jointly by the Siberian and Ural Branches of the Russian Academy of Sciences, by Siberian Federal University (project no. s/b S-11), and by the Ministry of Education and Science of the Russian Federation (state contract no. P891, federal program "Human Capital"). E.I.Sh. acknowledges the support of the Dynasty Foundation.
Предметные рубрики: BAND HUBBARD-MODEL
COPPER OXIDES
ELEMENTARY EXCITATIONS
SPIN
ELECTRON
STATE
T/U
Аннотация: The effect of non-Heisenberg four-spin ring exchange on the superconducting transition temperature in strongly correlated electron systems is studied. It is shown that the ring exchange can significantly suppress the contribution of the Heisenberg exchange to superconducting pairing.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Popkov S. I., Semenov S. V., Bykov A. A., Sabitova E. I., Dubrovskiy A. A., Shaikhutdinov K. A., Petrov M. I.
Заглавие : Contributions from Inter-grain Boundaries to the Magneto-resistive Effect in Polycrystalline High-T (C) Superconductors. The Underlying Reason of Different Behavior for YBCO and BSCCO Systems
Разночтения заглавия :авие SCOPUS: Contributions from inter-grain boundaries to the magneto-resistive effect in polycrystalline high-TC superconductors. the underlying reason of different behavior for YBCO and BSCCO systems
Место публикации : J. Supercond. Nov. Magn: SPRINGER, 2011. - Vol. 24, Is. 7. - P2129-2136. - ISSN 1557-1939, DOI 10.1007/s10948-011-1166-9
Примечания : Cited References: 30. - This work is supported by program N5 of RAS, project N7.
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
PHASE-SLIP
TRANSPORT-PROPERTIES
TRANSITION
FIELD
COMPOSITES
BULK
TAPES
YBA2CU3O7-DELTA
DISSIPATION
Ключевые слова (''Своб.индексиров.''): bscco--ybco--intergrain boundaries--magnetoresistance--bscco--intergrain boundaries--magnetoresistance--ybco--bscco--bscco system--comparative studies--high tc superconductors--high-field--inter-grain--irreversibility lines--magneto-resistive effect--polycrystalline--resistive transition--standard measurements--weak pinning--ybco--bismuth--electric resistance--grain boundaries--high temperature superconductors--lead--magnetic fields--magnetoelectronics--magnetoresistance--magnetos--superconductivity--yttrium barium copper oxides--semiconductor metal boundaries
Аннотация: In order to clarify the mechanisms in charge of broadening of resistive transition R(T) in magnetic fields of bismuth-based polycrystalline high-T (C) superconductor (HTSC), a comparative study of Bi1.8Pb0.3Sr1.9Ca2Cu3O (x) (BSCCO) and YBa2Cu3O7-delta (YBCO) have been performed. Magnetoresistive effects and irreversibility line obtained from magnetic measurements have been studied. It was established that (1) for YBCO, the smooth part of R(T) dependence unambiguously corresponds to dissipation in the intergrain boundaries for arbitrary magnetic fields; (2) for polycrystalline BSCCO, the smooth part of R(T) dependences correspond to dissipation within intergrain boundary subsystem in the field range H 10(2) Oe only, while standard measurements of R(T) dependences in magnetic field range H 10(2) Oe reflect the dissipation processes occurring both in intergrain boundary and HTSC grain subsystems; (3) for the high-field range, the contribution from intergrain boundaries of BSCCO can be distinguished from magnetoresistance R(H) dependences obtained at high enough current density on textured samples. It is proposed that various magneto-resistive properties of these classical HTSC systems are due comparatively weak pinning in BSCCO.
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16.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Drokina T. V., Petrakovskii G. A., Molokeev M. S., Misyul S. V., Bondarev V. S., Velikanov D. A., Frontzek M., Schefer J.
Заглавие : Crystal and magnetic structures, phase transitions in quasi-onedimensional pyroxenes Na0.5Li 0.5FeGe2O6
Коллективы : International Workshop on Phase Transitions and Inhomogeneous States in Oxides, "Фазовые переходы и неоднородные состояния в оксидах", международный семинар
Место публикации : Int. Workshop on Phase Transit. and Inhomogeneous States in Oxides: book of abstracts. - Kazan, 2015. - P.54
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Beznosikov B. V., Aleksandrov K. S.
Заглавие : Crystal chemistry and structure of expected compounds A2BX4. II. Oxides, selenides, and sulfides 061A2B6+X4 2- and 080A2 2+B4+X4 2-.
Место публикации : Sov. Phys.: Crystallogr. - 1985. - Vol. 30, Is. 5. - P.533-535; \b Crystallography Reports; \b Kristallografiya
Аннотация: Predictions of A2BX4 compounds for compositions 071A2 +B6+X4 2- with type structures of K2MgF4, beta -K2SO4, spinel, olivine, thenardite, phenacite, Sr2PbO4, and Pb3O4 are presented. K2MgF4 type structures are known and probable only in oxides and sulphides with hexavalent uranium because their formation is limited by the size of the hexavalent B cation. Structures of the beta -K2SO4 type are stable in compounds with large A cations. Among the sulphides with 076A2 +B6+X4 2-, the spinel crystal structure is as yet unknown, but is most probable in compounds with A+ = Li, Na, Ag, and with B6+ = Mo, W, and U. The olivine type structure is known only in Ag2CrO4, and no new compounds with this structure are expected to be found. A phenacite structure is probable only in three new oxides and in some sulphides with Li as A+. A thenardite type structure is probable in oxides with B6+ = Fe and Mn, but sulphides are unlikely. For 076A2 2+B4+X4 2- compounds with large A2+ ions and B4+ ions with radii from 0.57 A to RB 0.48RA + 0.11, a K2MgF4 structure would exist. For even larger A ions, the Sr2PbO4 structure would exist. In oxides with cations A2+ = Pb and Sn, compounds with Pb3O4 type structures are probable.-D.F.P.
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18.

19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Moshkina E. M., Seryotkin Y., Bovina A. F., Molokeev M. S., Eremin E. V., Belskaya N., Bezmaternykh L. N.
Заглавие : Crystal formation of Cu-Mn-containing oxides and oxyborates in bismuth-boron fluxes diluted by MoO3 and Na2CO3
Место публикации : J. Cryst. Growth. - 2018. - Vol. 503. - P.1-8. - ISSN 00220248 (ISSN), DOI 10.1016/j.jcrysgro.2018.09.011
Примечания : Cited References: 26. - This study was supported by Russian Foundation for Basic Research (RFBR) according to the research project No. 17-02-00953 A.
Ключевые слова (''Своб.индексиров.''): characterization--growth from solutions--single crystal growth--manganites--magnetic materials
Аннотация: The high-temperature crystallizing phases of fluxes (molten solutions) based on Bi2O3:MoO3 = 1:3 and diluted by Na2CO3 and B2O3 (under varying of Na2CO3:B2O3), and by CuO and Mn2O3 (0 ≤ Mn2O3:CuO ≤ 5) are studied. The conditions of the stable crystallization of Mn2+1−xCuxMoO4, Mn23+O3, Mn2+Mn23+O4, Mn2+1−xCuxMn3+BO4 and Mn2+2−xCuxMn3+BO5 have been found. The influence of MoO3 and Na2CO3 to the crystallization processes of Mn2+- and Mn3+-containing Mn2+1−xCuxMoO4 and Mn2+Mn23+O4 and Mn23+O3 are clarified. The occurrence of the chemical bonds of these types at the crystallization of Mn-heterovalent Mn2+1−xCuxMn3+BO4 and Mn2+2−xCuxMn3+BO5 oxyborates is studied. Single crystal growth techniques of these oxyborates are suggested. The results of the structural and magnetic characterization of some discussed compounds are presented.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Orlov Yu. S., Solovyov L. A., Vereshchagin S. N., Ustyuzhanin Yu. N., Zharkov S. M., Zeer G. M., Borus A. A., Bondarev V. S., Ovchinnikov S. G.
Заглавие : Crystal structure and thermoelectric properties of mechanically activated LaCoO3
Место публикации : J. Taiwan Inst. Chem. Eng. - 2024. - Vol. 162. - Ст.105560. - ISSN 18761070 (ISSN), DOI 10.1016/j.jtice.2024.105560. - ISSN 18761089 (eISSN)
Примечания : Cited References: 88. - This study was supported by the Russian Science Foundation , project no. 24-22-00091
Аннотация: Background: Crystal structure of rare-earth LaCoO3 cobalt oxide subjected to high energy mechanical activation has been studied. In the temperature range of 300–800 K, the electrical conductivity and Seebeck coefficient were measured. Thermal conductivity was measured at 300–480 K. Methods: Comparative analysis of thermoelectric properties of the samples prepared by standard solid-state reaction and using high-energy mechanical activation was carried out. Findings: It was found that the experimental X-ray diffraction patterns are best described within the model that allows the coexistence of two domains in samples with the same crystal symmetry, but different lattice a and c parameters. The percentage ratio of these domains in the samples depends significantly on the size of the initial particles in the solid-state synthesis reaction and the annealing temperature. Mechanical activation and increase of synthesis temperature result in change of Seebeck coefficient sign and significant decrease of electrical resistivity. The Seebeck coefficient of non-activated samples takes positive values over the entire temperature range and decreases monotonically with increasing temperature, in contrast to mechanically activated samples exhibiting ambipolar behavior.
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