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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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Zobov, V. E.
On the radius of convergence of series in powers of time for spin correlation functions of the Heisenberg magnet at high temperature / V. E. Zobov, M. A. Popov // Theor. Math. Phys. - 1997. - Vol. 112, Is. 3. - P. 1182-1191, DOI 10.1007/BF02583049. - Cited References: 22 . - ISSN 0040-5779

РУБ Physics, Multidisciplinary + Physics, Mathematical
Рубрики:
AUTO-CORRELATION FUNCTION
   INFINITE-TEMPERATURE
   PARAMAGNET
   DYNAMICS
   MODEL
Аннотация: The convergence of series in powers of time for spin autocorrelation functions of the Heisenberg magnet are investigated at infinite temperatures on lattices of different dimensions d. The calculation data available at the present time for the coefficients of these series are used to estimate the corresponding radii of convergence, whose growth with decreasing d is revealed and explained in a self-consistent approximation. To this end, a simplified nonlinear equation corresponding to this approximation is suggested and solved for the autocorrelation function of a system with an arbitrary number Z of nearest neighbors. The coefficients of the expansion in powers of time for the solution are represented in the form of trees on the Bethe lattice with the coordination number Z. A computer simulation method is applied to calculate the expansion coefficients for trees embedded in square, triangular, and simple cubic lattices under the condition that the intersection of tree branches is forbidden. It is found that the excluded volume effect that manifests itself in a decrease in these coefficients and in an increase in the coordinate and exponent of the singularity of the autocorrelation function on the imaginary time axis is intensified with decreasing lattice dimensions.

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk, Russia
Krasnoyarsk State Univ, Krasnoyarsk, Russia
ИФ СО РАН

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич
}
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Zobov, V. E.
On the coordinate of a singular point of the time correlation function for a spin system on a simple hypercubic lattice at high temperatures / V. E. Zobov, M. A. Popov // Theor. Math. Phys. - 2002. - Vol. 131, Is. 3. - P. 862-872, DOI 10.1023/A:1015935809388. - Cited References: 19 . - ISSN 0040-5779

РУБ Physics, Multidisciplinary + Physics, Mathematical
Рубрики:
NUCLEAR-DOUBLE-RESONANCE
   HEISENBERG MAGNET
   DEPENDENCE
   MODEL
Кл.слова (ненормированные):
spin dynamics -- correlation functions -- power series in time -- frequency moments -- singular points -- generated functions -- lattice trees -- multidimensional expansion -- Correlation functions -- Frequency moments -- Generated functions -- Lattice trees -- Multidimensional expansion -- Power series in time -- Singular points -- Spin dynamics
Аннотация: Using the d(-1) expansion method (d is the space dimension), we estimate the coordinate of the time-dependent autocorrelation function singular point on the imaginary time axis for the spin 1/2 Heisenberg model on a simple hypercubic lattice at high temperatures. We represent the coefficients of the time expansion (the spectral moments) for the autocorrelation function as the sums of the weighted lattice figures in which the trees constructed from the double bonds give the leading contributions with respect to d(-1) and the same trees with the built-in squares from six bonds or diagrams with the fourfold bonds give the contribution of the next-to-leading order. We find the corrections to the coordinate of the autocorrelation function singular point that are due to the latter contributions.

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Держатели документа:
RAS, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, RAS, Krasnoyarsk, Russian Federation
Kirensky State University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич
}
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Zinenko, V. I.
Statistical mechanics of cation ordering in PbSc1/2Ta1/2O3 and PbSc1/2Nb1/2O3 solid solutions / V. I. Zinenko, S. N. Sofronova // Phys. Solid State. - 2005. - Vol. 47, Is. 12. - P. 2309-2314, DOI 10.1134/1.2142896. - Cited References: 17 . - ISSN 1063-7834

РУБ Physics, Condensed Matter
Рубрики:
PHASE-TRANSITION
   PEROVSKITE
   DISORDER
   FERROELECTRICS
   CRYSTALS
   MODEL
Аннотация: A model Hamiltonian for B cation ordering (Sc-Nb(Ta)) in PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3 solid solutions is constructed. The parameters of the model Hamiltonian are determined from the ab initio calculation within the ionic crystal model with allowance made for the deformability and the dipole and quadrupole polarizabilities of the ions. The temperatures of the phase transition due to the ordering of the B cations are calculated by the Monte Carlo method in the mean-field and cluster approximations. The phase transition temperatures calculated by the Monte Carlo method (1920 K for PbSc1/2Ta1/2O3 and 1810 K for PbSc1/2Nb1/2O3) are consistent with the experimental data (1770 and 1450 K, respectively). The thermodynamic properties of the cation ordering are investigated using the Monte Carlo method. (c) 2005 Pleiades Publishing, Inc.

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

Доп.точки доступа:
Sofronova, S. N.; Софронова, Светлана Николаевна; Зиненко, Виктор Иванович
}
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    Val'kov, V. V.
    The modification of low-temperature magnetic properties of the Fe-based double-zigzag single-chain magnet under irradiation / V. V. Val'kov, M. S. Shustin // J. Magn. Magn. Mater. - 2017. - Vol. 440. - P. 19-22, DOI 10.1016/j.jmmm.2016.12.100. - Cited References: 14. - This study was supported by the Presidium of the Russian Academy of Sciences, program Actual problems of low temperature physics (project 0358-2015-0005); the Russian Foundation for Basic Research, projects nos. 16-42-243057 (partly with Government of Krasnoyarsk Territory) and 15-42-04372; Technology Support Fund to the research project nos. 14/16. The work of M.S.S. was supported by grant of the President of the Russian Federation (project MK-1398.2017.2). . - ISSN 0304-8853
   Перевод заглавия: Модификация низкотемпературных свойств железо содержащего одноцепочечного магнетика с магнитной топологией двойного зигзага

РУБ Materials Science, Multidisciplinary + Physics, Condensed Matter
Рубрики:
SPIN-CROSSOVER
MODEL
Кл.слова (ненормированные):
Single-chain magnets -- Light-induced spin crossover -- Magnetic susceptibility -- Quantum phase transitions
Аннотация: An exact solution for a generalized Ising model describing single-chain magnet {[FeIII(Tp*)(CN)3]2FeII(bpmh)}·2H2O with alternating high-spin and low-spin iron ions and double-zigzag magnetic topology has been calculated making use of the transfer-matrix technique. The introduction of a statistical ensemble taking into account the presence of iron ions with high-spin (HS) and low-spin (LS) states made it possible to describe the modification of magnetic susceptibility under optical irradiation. It has been shown that joint implementation of iron ions with photoinduced magnetic states and non-magnetic intersite repulsion ions of these states is caused by the difference of the ionic radii of HSFeIIHSFeII and LSFeIILSFeII leads to the quantum phase transitions in the system.

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Доп.точки доступа:
Shustin, M. S.; Шустин, Максим Сергеевич; Вальков, Валерий Владимирович; Euro-Asian Symposium "Trends in MAGnetism"(6 ; 2016 ; Aug. ; 15-19 ; Krasnoyarsk); "Trends in MAGnetism", Euro-Asian Symposium(6 ; 2016 ; Aug. ; 15-19 ; Krasnoyarsk); Институт физики им. Л.В. Киренского Сибирского отделения РАН
}
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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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    Val'kov, V. V.
    Spectral representations and description of a superconducting state with S-type order parameter Delta(k) / V. V. Val'kov, D. M. Dzebisashvili, A. S. Kravtsov // JETP Letters. - 2003. - Vol. 77, Is. 9. - P. 505-509, DOI 10.1134/1.1591980. - Cited References: 11 . - ISSN 0021-3640
Рубрики:
GREENS FUNCTIONS
   MODEL
Аннотация: The inclusion of a singular contribution to the spectral intensity of the anomalous correlation function is shown to regain the sum rule and remove the unjustified forbidding of the S-symmetry order parameter in superconductors with strong correlations. For the order parameter of this symmetry, the solution to the self-consistency equation is analyzed beyond the nearest-neighbor approximation. (C) 2003 MAIK "Nauka / Interperiodica".

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Публикация на русском языке Вальков, Валерий Владимирович. Спектральные представления и проблема описания сверхпроводящего состояния с S-типом симметрии параметра порядка Δ(k) [Текст] / В. В. Вальков, Д. М. Дзебисашвили, А. С. Кравцов // Письма в "Журн. эксперим. и теор. физ.". - 2003. - Т. 77 Вып. 9. - С. 604-608

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

Доп.точки доступа:
Dzebisashvili, D. M.; Дзебисашвили, Дмитрий Михайлович; Kravtsov, A. S.; Вальков, Валерий Владимирович
}
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Val'kov, V. V.
Radiation-induced modification of the temperature dependence of the magnetic susceptibility of a 1D magnet / V. V. Val'kov, M. S. Shustin // JETP Letters. - 2014. - Vol. 100, Is. 7. - P. 455-462, DOI 10.1134/S0021364014190138. - Cited References: 28. - This work was supported by the Russian Foundation for Basic Research, project nos. 12-02-31130, 13-02-00523, and 13-02-98013. . - ISSN 0021-3640. - ISSN 1090-6487

РУБ Physics, Multidisciplinary
Рубрики:
SINGLE-CHAIN MAGNETS
   EASY-PLANE
   ARRANGEMENT
   MODEL
   IONS
Аннотация: TThe excitation spectrum of a catena-[FeII(ClO4)2{FeIII(bpca)2}]ClO4 anisotropic 1D magnet with alternating high-spin and low-spin iron ions has been calculated with the use of the diagrammatic technique for Hubbard operators. This has allowed establishing conformity with the Ising model, for which the magnetic susceptibility has been calculated by the transfer-matrix method. The introduction of a statistical ensemble taking into account the presence of chains with different lengths and iron ions with different spins has allowed describing the modification of the magnetic susceptibility under optical irradiation.

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Публикация на русском языке Вальков, Валерий Владимирович. Модификация температурной зависимости магнитной восприимчивости 1D-магнетика под действием облучения [Текст] / В. В. Вальков, М. С. Шустин // Письма в Журн. эксперим. и теор. физ. : Наука, 2014. - Т. 100 Вып. 7. - С. 510-517

Держатели документа:
Russian Acad Sci, Siberian Branch, Kirensky Inst Phys, Krasnoyarsk 660036, Russia
Siberian Fed Univ, Krasnoyarsk 660041, Russia

Доп.точки доступа:
Shustin, M. S.; Шустин, Максим Сергеевич; Вальков, Валерий Владимирович; Russian Foundation for Basic Research [12-02-31130, 13-02-00523, 13-02-98013]
}
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    Val'kov, V. V.
    Origin of the spin polaron quasiparticles and their cooper instability in High-Tc superconductors / V. V. Val'kov, D. M. Dzebisashvili, A. F. Barabanov // J. Supercond. Nov. Magn. - 2016. - Vol. 29, Is. 4. - P. 1049-1055, DOI 10.1007/s10948-016-3383-8. - Cited References:15. - This study was supported by the Russian Foundation for Basic Research, projects nos. 13-02-00523, 13-02-00909 and the Dynasty Foundation. . - ISSN 1557-1939. - ISSN 1557-1947
   Перевод заглавия: Природа спин-поляронных квазичастиц и их куперовской неустойчивости в высокотемпературных сверхпроводниках

РУБ Physics, Applied + Physics, Condensed Matter
Рубрики:
Model
State
Кл.слова (ненормированные):
Cuprate High-T-c superconductors -- Spin polarons -- Spin-fermion model
Аннотация: IIn the framework of the spin-fermion model, it is shown that accounting for the strong spin-charge fluctuations between holes of copper and oxygen ions in cuprate High-T c superconductors leads to the formation of the Fermi spin-polaron quasiparticles. It is demonstrated that the large value of the binding energy of such quasiparticle is determined by the processes in which hopping intensity of the oxygen holes depends significantly on the spin configuration of holes on the copper and oxygen ions. It was found that the ensemble of such quasiparticles manifests Cooper instability and the concentration dependence of the critical temperature is in good agreement with the experimental data.

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Держатели документа:
SB RAS, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia.
RAS, Inst High Pressure Phys, Troitsk 142098, Moscow Region, Russia.

Доп.точки доступа:
Dzebisashvili, D. M.; Дзебисашвили, Дмитрий Михайлович; Barabanov, A. F.; Вальков, Валерий Владимирович; Russian Foundation for Basic Research [13-02-00523, 13-02-00909]; Dynasty Foundation
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10.

    Val'kov, V. V.
    Nature of Cooper instability of spin polarons in cuprate high-Tc superconductors / V. V. Val'kov, D. M. Dzebisashvili, A. F. Barabanov // J. Low Temp. Phys. - 2015. - Vol. 181, Is. 3-4. - P. 134-138, DOI 10.1007/s10909-015-1331-9. - Cited References:10. - This study was supported by the Russian Foundation for Basic Research, Projects Nos. 13-02-00523, 13-02-00909 and the Dynasty Foundation. . - ISSN 0022. - ISSN 1573-7357
   Перевод заглавия: Природа куперовской неустойчивости спиновых поляронов в купратных высокотемпературных сверхпроводниках

РУБ Physics, Applied + Physics, Condensed Matter
Рубрики:
OXIDES
MODEL
Кл.слова (ненормированные):
High-T-c superconductors -- Spin polarons -- Spin-fermion model
Аннотация: It is shown that the exchange interaction in the subsystem of localized moments of copper ions can trigger a Cooper instability in the ensemble of spin-polaron quasiparticles in cuprate high-temperature superconductors. It is important that, inherent to cuprates, strong coupling between Fermi and spin degrees of freedom leads on the one hand to formation of spin-polaron quasiparticles and, on the other hand, allows to transfer the interaction between Bose degrees of freedom onto the interaction between Fermi quasiparticles. The solution of the integral equation for the d-wave superconducting order parameter is well consistent with the available experimental data.

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia.
MF Reshetnev Siberian State Aerosp Univ, Krasnoyarsk 660014, Russia.
Russian Acad Sci, Inst High Pressure Phys, Troitsk 142092, Moscow Region, Russia.

Доп.точки доступа:
Dzebisashvili, D. M.; Дзебисашвили, Дмитрий Михайлович; Barabanov, A. F.; Вальков, Валерий Владимирович; Russian Foundation for Basic Research [13-02-00523, 13-02-00909]; Dynasty Foundation
}
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