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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev A. D., Berzhanskii V. N., Valkov V. V., Ovchinnikov S. G., Chernov V. K.
Заглавие : Deviation from the bloch law in ferromagnetic materials with an intermediate valence
Место публикации : JETP Letters. - 1981. - Vol. 34, Is. 5. - P.255-258. - ISSN 0021-3640
Примечания : Cited References: 6
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Furrer A., Fisher P., Roessli B., Petrakovskii G. A., Sablina K. A., Valkov V. V., Fedoseev B.
Заглавие : Investigation of spin-waves in single-crystal Bi2CuO4 by inelastic neutron-scattering
Место публикации : Solid State Commun. - 1992. - Vol. 82, Is. 6. - P.443-446. - ISSN 0038-1098, DOI 10.1016/0038-1098(92)90746-V
Примечания : Cited References: 9
Аннотация: Neutron scattering experiments have been employed to study the spin-wave excitations and the critical behaviour of sublattice magnetization of a single crystal Bi2CuO4. Dispersion law for spin waves along the tetragonal axis of crystal is determined. There were found two branches of spin waves which are characterized by the energy gaps DELTA-1 congruent-to 1.7 meV and DELTA-2 congruent-to 4.0 meV, respectively. The value of critical exponent beta = 0.36 + 0.08 reflects the 3D character of the magnetic ordering in Bi2CuO4. Observed two spin-wave branches are described on the basis of the anisotropic tetragonal spin-Hamiltonian with four-sites exchange interaction.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Valkov V. V.
Заглавие : Anomalous resistivity and superconductivity in the two-band Hubbard model with one narrow band (Review)
Место публикации : Low Temp. Phys. - 2011. - Vol. 37, Is. 1. - P.69-82. - ISSN 1063-777X, DOI 10.1063/1.3552118; \b Физика низких температур
Примечания : Cited References: 62. - We thank A.S. Alexandrov, A.F. Andreev, M.A. Baranov, Yu. Bichkov, A.V. Chubukov, D.V. Efremov, A.S. Hewson, K.A. Kikoin, F.V. Kusmartsev, P. Nozieres, T.M. Rice, A.O. Sboychakov, P. Thalmeer, C.M. Varma, D. Vollhardt, P. Woelfle, A. Yaresko and, especially, P. Fulde, Yu. Kagan, K.I. Kugel, and N.V. Prokof'ev for many simulating discussions on this subject and acknowledge the financial support of RFBR grants # 08-02-00224 and 08-02-00212. M.Yu.K. is also grateful to the Leverhulme trust for a grant to visit Loughborough University, where this work was completed.
Предметные рубрики: FERMI-LIQUID BEHAVIOR
MAGNETIC-ALLOYS
HEAVY
DENSITY
SYSTEMS
STATE
UPT3
MECHANISM
PARTICLE
VALENCE
Аннотация: We search for marginal Fermi-liquid behavior in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron-polaron effects and other mechanisms for mass-enhancement (related to the momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find a tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case with a large mismatch between the densities of heavy and light bands in the strong coupling limit. We also find that for low temperatures and equal densities, the resistivity in a homogeneous state R(T) proportional to T-2 behaves as a Fermi-liquid in both 3D and 2D. For temperatures greater than the effective bandwidth for heavy electrons T W-h*, the coherence of the heavy component breaks down completely. The heavy particles move diffusively in the surrounding light particles. At the same time, light particles scatter on heavy particles as if on immobile (static) impurities. Under these conditions, the heavy component is marginal, while the light component is not. The resistivity approaches saturation for T W-h* in the 3D case. In 2D the resistivity has a maximum and a localization tail owing to weak-localization corrections of the Altshuler-Aronov type. This behavior of resistivity in 3D could be relevant for some uranium-based heavy-fermion compounds such as UNi2Al3 and in 2D, for some other mixed-valence compounds, possibly including layered manganites. We also consider briefly the superconductive (SC) instability in this model. The leading instability tends to p-wave pairing and is governed by an enhanced Kohn-Luttinger mechanism for SC at low electron densities. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light electrons in 2D. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552118]
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : BABKIN E. V., CHERKUNOVA N. G., Ovchinnikov S. G., Valkov V. V.
Заглавие : QUANTUM SIZE EFFECT IN MAGNETITE THIN-FILMS
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1983. - Vol. 25, Is. 6. - P1896-1898. - ISSN 0367-3294
Примечания : Cited References: 4
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5.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Valkov V. V., Valkova T. A., Jolobova N. N.
Заглавие : The influence of the quantum fluctuations on the ground state and spectral properties of 2D magnets with cubic symmetry four-spin exchange interactions
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. - Ст.23PO-12-5. - p.510-511
Примечания : This work was supported by the program of Presidium of RAS Quantum macrophysics, Russian Foundation for Basic Research (project no. 07-02-00226), and Integration project 3.4 SB RAS
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Valkov V. V., Ovchinnikov S. G., Petrakovskii G. A.
Заглавие : 2-MAGNON EXCITATION SPECTRUM IN AN EASY AXIS QUASI TWO-DIMENSIONAL FERROMAGNET
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1988. - Vol. 30, Is. 10. - P3044-3047. - ISSN 0367-3294
Примечания : Cited References: 6
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : VALKOV V. V., MATSULYEVA G. N.
Заглавие : ANGULAR-DEPENDENCE OF FMR FREQUENCY IN STRONGLY ANISOTROPIC UNIAXIAL FERROMAGNETICS
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1988. - Vol. 94, Is. 1. - P217-226. - ISSN 0044-4510
Примечания : Cited References: 35
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Valkov V. V., Valkova T. A.
Заглавие : Anomalies in the quantum excitation spectrum of a magnetic material with a strong quasi-particle interaction
Место публикации : JETP Letters. - 1990. - Vol. 52, Is. 11. - P.589-592. - ISSN 0021-3640
Примечания : Cited References: 6
Предметные рубрики: SUPERCONDUCTIVITY
Аннотация: It is shown in a nonlinear theory that the quantum spectrum of excitations becomes analogous to the spectrum of excitations of a quantum Bose liquid in the case of a highly anisotropic ferromagnet, with a large number of interacting quasiparticles.
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9.

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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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Valkov V. V., Ovchinnikov S. G.
Заглавие : CONTRIBUTION OF MAGNON-MAGNON INTERACTION TO THERMODYNAMICS OF ANISOTROPIC FERROMAGNETS
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1983. - Vol. 85, Is. 5. - P1666-1674. - ISSN 0044-4510
Примечания : Cited References: 19
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