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Mechanisms of dissipation in a Josephson medium based on a high-temperature superconductor in a magnetic field / D. A. Balaev [et al.] // Phys. Solid State. - 2006. - Vol. 48, Is. 5. - P. 826-832, DOI 10.1134/S1063783406050039. - Cited References: 32 . - ISSN 1063-7834

РУБ Physics, Condensed Matter
Рубрики:
RESISTIVE TRANSITION
   PHASE-SLIP
   TRANSPORT-PROPERTIES
   MAGNETORESISTANCE
   SYSTEM
   MODEL
   YBA2CU3O7-X
   PENETRATION
   COMPOSITES
   HYSTERESIS
Аннотация: This paper reports on the results of an investigation into the influence of magnetic fields (0-60 kOe) on the temperature dependences of the electrical resistance R(T) of the Y3/4Lu1/4Ba2Cu3O7 + CuO composites. The structure of these composites is considered to be a network of tunnel-type Josephson junctions in which a nonsuperconducting component (CuO) forms boundaries (barriers) between high-temperature superconducting crystallites. The temperature dependence R(T) of the composites has two steps characteristic of granular superconductors: (i) an abrupt change in the electrical resistance at the critical temperature of high-temperature superconducting crystallites and (ii) a smooth transition to the superconducting state under the influence of the boundaries between the crystallites. The experimental dependences R(T) are analyzed within the Ambegaokar-Halperin model of thermal fluctuations in Josephson junctions and the flux creep model. An increase in the magnetic field leads to a crossover from the Ambegaokar-Halperin mechanism to the flux creep mechanism. The temperature dependences R(T) in the range of weak magnetic fields (from 0 to 10(2) Oe) are adequately described by the relationship following from the Ambegaokar-Halperin model. In the range of strong magnetic fields (from 10(3) to 6 x 10(4) Oe), the dissipation obeys the Arrhenius law R similar to exp(-U(H)/T)], which is characteristic of the flux creep model with a temperature-independent pinning energy U(H). The effective Josephson coupling energies and the pinning energies corresponding to the Ambegaokar-Halperin and flux creep mechanisms are determined.

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Держатели документа:
Russian Acad Sci, Siberian Div, Kirensky Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Balaev, D. A.; Балаев, Дмитрий Александрович; Popkov, S. I.; Попков, Сергей Иванович; Shaikhutdinov, K. A.; Шайхутдинов, Кирилл Александрович; Petrov, M. I.; Петров, Михаил Иванович
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The mechanisms responsible for broadening of the resistive transition under magnetic field in the Josephson junction network realized in bulk YBCO+CuO composites / D. A. Balaev [et al.] // Physica C. - 2006. - Vol. 435, Is. 1-2. - P. 12-15, DOI 10.1016/j.physc.2006.01.008. - Cited References: 15 . - ISSN 0921-4534

РУБ Physics, Applied
Рубрики:
SUPERCONDUCTORS
MODEL
Кл.слова (ненормированные):
Josephson network -- YBCO plus CuO composites -- dissipation -- magnetic field -- Dissipation -- Josephson network -- Magnetic field -- YBCO + CuO composites -- Composite materials -- Copper compounds -- Mathematical models -- Phase transitions -- Semiconductor junctions -- Yttrium compounds -- Creep model -- Josephson network -- YBCO + CuO composites -- Magnetic field effects
Аннотация: The experimental results of the effect of the magnetic field (up to 60 kOe) on the broadening of the resistive transition of bulk composites Y3/4Lu1/4Ba2CU3O7 (YBCO) + CuO are presented. These composites represent the network of the tunnel-type Josephson junctions where the copper oxide acts as a material forming barriers between YBCO crystallites. The mechanisms responsible for broadening of the resistive transition under magnetic field are discussed. The analysis of experimental R(7) dependences have shown that in the low field range 0-10(2) Oe, the R(7) dependences are described well by the Ambegaokar-Halperin (AH) model. In the range 10(3)-6 x 10(4) Oe, the dissipation follows Arrhenius law R similar to exp(-U(H)/k(B)T) characteristic for thermally activated flux creep model. In the range H similar to 10(2)-10(3), the crossover from AH to flux creep dissipation mechanisms occurs. (c) 2006 Elsevier B.V. All rights reserved.

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Держатели документа:
LV Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirensky Institute of Physics, 660036 Krasnoyarsk, Russian Federation

Доп.точки доступа:
Balaev, D. A.; Балаев, Дмитрий Александрович; Popkov, S. I.; Попков, Сергей Иванович; Shaihutdinov, K. A.; Petrov, M. I.; Петров, Михаил Иванович; International Workshop on Weak Superconductivity(2005 ; Sept. ; 16-19 ; Bratislava, Slovakia)
}
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Gavrichkov, V. A.
The role of orbital ordering in the formation of electron structure in undoped LaMnO3 manganites in the regime of strong electron correlations / V. A. Gavrichkov, S. G. Ovchinnikov, L. E. Yakimov // J. Exp. Theor. Phys. - 2006. - Vol. 102, Is. 6. - P. 972-985, DOI 10.1134/S1063776106060112. - Cited References: 25 . - ISSN 1063-7761

РУБ Physics, Multidisciplinary
Рубрики:
COLOSSAL MAGNETORESISTIVE OXIDES
   DOUBLE EXCHANGE
   BAND
   MODEL
Кл.слова (ненормированные):
Computational methods -- Correlation methods -- Doping (additives) -- Electrons -- Ferromagnetic materials -- Lanthanum compounds -- Paramagnetic materials -- Intraatomic electron correlations -- Mott Hubbard correlation gap -- Orbital ordering -- Paramagnetic phases -- Electronic structure
Аннотация: The electron structure of undoped LaMnO3 and slightly doped La1-xSrxMnO3 manganites has been calculated within the framework of a generalized tight binding method with explicit allowance for strong intra-atomic electron correlations. According to the results of these calculations, the ground state in orbitally disordered undoped LaMnO3 ferromagnets would be metallic despite the Mott-Hubbard correlation gap in the spectrum of quasiparticles. Owing to the orbital ordering, the insulating state is stabilized in both antiferromagnetic and paramagnetic phases. In-gap states of a polaron nature with a spectral weight proportional to the dopant concentration have been found near the top of the valence band in La1-xSrxMnO3. As the doping level increases, a metal state appears in the ferromagnetic phase, which has a metallic character for one spin subband and an insulating character for the other subband (representing the so-called half-metallic state).

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Публикация на русском языке Гавричков, Владимир Александрович. Роль орбитального упорядочения в формировании электронной структуры недопированных манганитов LaMnO3 в режиме сильных электронных корреляций [Текст] / В. Г. Архипкин, С. А. Мысливец, И. В. Тимофеев // Журн. эксперим. и теор. физ. - 2006. - Т. 129 Вып. 6.- P.1103-1117

Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
Siberian State Aerosp Univ, Krasnoyarsk 660014, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, 660036, Russian Federation
Siberian State Aerospace University, Krasnoyarsk, 660014, Russian Federation

Доп.точки доступа:
Ovchinnikov, S. G.; Овчинников, Сергей Геннадьевич; Yakimov, L. E.; Гавричков, Владимир Александрович
}
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Zobov, V. E.
Second moment of multiple-quantum NMR and a time-dependent growth of the number of multispin correlations in solids / V. E. Zobov, A. A. Lundin // J. Exp. Theor. Phys. - 2006. - Vol. 103, Is. 6. - P. 904-916, DOI 10.1134/S1063776106120089. - Cited References: 39 . - ISSN 1063-7761

РУБ Physics, Multidisciplinary
Рубрики:
NUCLEAR-MAGNETIC-RESONANCE
   LINE-SHAPE
   SPIN SYSTEMS
   DYNAMICS
   SPECTRA
   COHERENCES
   STATE
   BEHAVIOR
   CRYSTAL
   MODEL
Кл.слова (ненормированные):
Correlation methods -- Mathematical models -- Nuclear magnetic resonance spectroscopy -- Spectrum analysis -- Time series analysis -- Four-spin time correlation -- Multispin correlations -- Second moment -- Time power series -- Quantum theory
Аннотация: The time evolution of multispin correlations (the growth of the number of correlated spins as a function of time) can be observed directly using the multiple-quantum nuclear magnetic resonance spectroscopy of solids. A quantity related to this number, namely, the second moment of the intensity distribution of coherences of different orders in the multiple-quantum spectrum can be calculated using the theory proposed in this work. An approach to the calculation of the four-spin time correlation function through which this moment is expressed is developed. The main sequences of contributions in the expansion of this function into a time power series are summed using the approximation of a large number of neighbors both for systems with a secular dipole-dipole interaction and for systems with a nonsecular effective interaction. An exponential dependence of is obtained. The value of is additionally calculated using an expansion in terms of orthogonal operators for three model examples corresponding to different limiting realizations of spin systems. It is shown that the results of the microscopic theory at least qualitatively agree with both the results obtained for model examples and experimental results obtained recently for adamantane.

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Держатели документа:
Russian Acad Sci, Siberian Div, Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
Russian Acad Sci, Semenov Inst Chem Phys, Moscow 117977, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, 660036, Russian Federation
Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 117977, Russian Federation

Доп.точки доступа:
Lundin, A. A.; Зобов, Владимир Евгеньевич
}
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Ignatchenko, V. A.
Effects of long-wave inhomogeneities of the exchange and elastic force constants in the framework of the coherent potential approximation / V. A. Ignatchenko, V. A. Felk // Phys. Rev. B. - 2006. - Vol. 74, Is. 17. - Ст. 174415, DOI 10.1103/PhysRevB.74.174415. - Cited References: 14 . - ISSN 1098-0121

РУБ Physics, Condensed Matter
Рубрики:
CRYSTALS
MODEL
Аннотация: The formalism of averaged Green's functions in the continuum is developed for spin waves in ferromagnets with inhomogeneities of the exchange constant and elastic waves in media with inhomogeneities of the force constant. The integral self-consisted equation in the coherent potential approximation is developed for taking into account effects of inhomogeneities of these nonlocal characteristics of the material on the wave spectrum in it. The obtained general results are applied to the study of effects of one-dimensional inhomogeneities of the exchange constant on the wave spectrum in a ferromagnet.

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Держатели документа:
SB RAS, LV Kirensky Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
L. V. Kirensky Institute of Physics SB RAS, 660036, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Felk, V. A.; Игнатченко, Вальтер Алексеевич
}
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Ovchinnikov, S. G.
Density of hole-doped states in strongly correlated electron-systems of copper oxides / S. G. Ovchinnikov // Phys. Rev. B. - 1994. - Vol. 49, Is. 14. - P. 9891-9897, DOI 10.1103/PhysRevB.49.9891. - Cited References: 34 . - ISSN 0163-1829

РУБ Physics, Condensed Matter
Рубрики:
DYNAMIC PROPERTIES
   SUPERCONDUCTIVITY
   GAP
   LA2CUO4
   BI2SR2CACU2O8
   PHOTOEMISSION
   SPECTROSCOPY
   SPECTRA
   MODEL
   BAND
Аннотация: A generalized tight-binding method to calculate quasiparticle band structure and density of states in strongly correlated systems is presented. The band structures of undoped and weakly hole-doped CuO2 layer are calculated. The insulator gap has a charge transfer nature with a minor contribution from a Cu-O Coulomb interaction. Doping results in the appearance of an in-gap state with a simultaneous decrease of the density of states at the band edges in agreement with small cluster results and experimental data.

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Держатели документа:
L. V. Kyrensky Institute of Physics, Siberian Branch of Russian Academy of Sciences, Krasnoyarsk 660036, Russian Federation

Доп.точки доступа:
Овчинников, Сергей Геннадьевич
}
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Deich, L. I.
Far-infrared attenuation in glasses / L. I. Deich // Phys. Rev. B. - 1994. - Vol. 49, Is. 1. - P. 109-113, DOI 10.1103/PhysRevB.49.109. - Cited References: 29 . - ISSN 0163-1829

РУБ Physics, Condensed Matter
Рубрики:
VITREOUS SILICA
   TEMPERATURE
   MODEL
   LOCALIZATION
   ABSORPTION
   SOLIDS
   STATES
Аннотация: The influence of quasilocal vibrations on the far-infrared spectra of glasses is investigated under the supposition that the quasilocal vibrations are directly inactive in the attenuation. It is shown that taking into account phonon-quasilocal-vibration coupling and both medium- and short-range structure of the inhomogeneities of a photon-phonon coupling parameter can give rise to an attenuation curve similar to one observed for a-SiO2 and related materials.

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Держатели документа:
L. V. Kirensky Institute of Physics, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Дейч, Лев Исаакович
}
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ORBITAL POLARIZATION IN METALLIC F-ELECTRON SYSTEMS / I. S. SANDALOV [et al.] // Phys. Rev. B. - 1995. - Vol. 51, Is. 20. - P. 13987-14000, DOI 10.1103/PhysRevB.51.13987. - Cited References: 28 . - ISSN 0163-1829

РУБ Physics, Condensed Matter
Рубрики:
MOTT INSULATORS
   VOLUME COLLAPSE
   CERIUM
   LOCALIZATION
   TRANSITION
   PHASES
   MODEL

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Держатели документа:
RUSSIAN ACAD SCI,KIRENSKY INST PHYS,KRASNOYARSK 660036,RUSSIA
ИФ СО РАН
Condensed Matter Theory Group, Institute of Physics, University of Uppsala, Uppsala, Sweden
Kirensky Institute of Physics, Russian Academy of Sciences, 660036 Krasnoyarsk, Russian Federation

Доп.точки доступа:
SANDALOV, I. S.; Сандалов, Игорь Семёнович; HJORTSTAM, O.; JOHANSSON, B.; ERIKSSON, O.
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Val'kov, V. V.
The magnetoelastic mechanism of singlet phase formation in a two-dimensional quantum antiferromagnet / V. V. Val'kov, V. A. Mitskan, G. A. Petrakovskii // J. Exp. Theor. Phys. - 2006. - Vol. 102, Is. 2. - P. 234-247, DOI 10.1134/S106377610602004X. - Cited References: 18 . - ISSN 1063-7761

РУБ Physics, Multidisciplinary
Рубрики:
GROUND-STATE
   SPIN
   TRANSITION
   CUGEO3
   MODEL
Кл.слова (ненормированные):
Crystal lattices -- Elasticity -- Mathematical models -- Oscillations -- Phase diagrams -- Phase transitions -- Quantum theory -- Two dimensional -- Atomic representation -- Magnetoelastic mechanism -- Quantum antiferromagnets -- Singlet phase formation -- Antiferromagnetic materials
Аннотация: A model describing the second-order phase transition with respect to the magnetoelastic coupling parameter from the anti ferromagnetic (AFM) to the singlet state in a two-dimensional quantum magnet on a square lattice is proposed. The spectrum of elementary excitations in the singlet and AFM phases is calculated using an atomic representation, and the evolution of transverse and longitudinal branches of this spectrum is studied in the vicinity of the transition point. It is established that the AFM to singlet phase transition is related to softening of the longitudinal branch of oscillations. In the singlet phase, the gap plays the role of a parameter characterizing the distance to the phase transition point. It is shown that the spectrum of transverse oscillations in the AFM phase corresponds to the Goldstone boson. Based on an analysis of the stability of the spectrum of elementary excitations, a phase diagram is constructed that determines the regions of the existence of phases with plaquette-deformed lattices.

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Держатели документа:
Russian Acad Sci, Siberian Div, Inst Phys, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660074, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660075, Russia
ИФ СО РАН
Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, 660036, Russian Federation
Krasnoyarsk State Technical University, Krasnoyarsk, 660074, Russian Federation
Krasnoyarsk State University, Krasnoyarsk, 660075, Russian Federation

Доп.точки доступа:
Mitskan, V. A.; Мицкан, Виталий Александрович; Petrakovskii, G. A.; Петраковский, Герман Антонович; Вальков, Валерий Владимирович
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10.

OVCHINNIKOV, S. G.
THE INFLUENCE OF THE ANTIFERROMAGNETISM ON THE ELECTRONIC-STRUCTURE OF LA2CUO4 / S. . OVCHINNIKOV // J. Supercond. - 1995. - Vol. 8: University-of-Miami Workshop on High-Temperature Superconductivity - Physical Properties and Mechanisms (JAN 05-11, 1995, CORAL GABLES, FL), Is. 5. - P. 675-676, DOI 10.1007/BF00727473. - Cited References: 15 . - ISSN 0896-1107

РУБ Physics, Applied + Physics, Condensed Matter
Рубрики:
OXIDES
MODEL
Кл.слова (ненормированные):
ELECTRON CORRELATIONS -- ELECTRON STRUCTURE -- SPIN FLUCTUATIONS -- Electron correlations -- electron structure -- spin fluctuations -- Antiferromagnetism -- Band structure -- Calculations -- Correlation theory -- Electrons -- Lanthanum compounds -- Paramagnetism -- Perturbation techniques -- Antiferromagnetic phase -- Electron correlations -- Intercluster interactions -- Spin fluctuations -- Electronic structure
Аннотация: The quasiparticle approach for electronic structure calculations considering strong electron correlations is given. The exact diagonalization of a multiband Hubbard Hamiltonian for a small cluster is combined with perturbation theory for intercluster hopping. The band structure of paramagnetic and antiferromagnetic La2CuO4 are discussed.

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Держатели документа:
L.V.Kirensky Institute of Physics, Krasnoyarsk, 660036, Russian Federation
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