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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Mankov Y. I., Maradudin A. A.
Заглавие : Wave spectrum of multilayers with finite thicknesses of interfaces
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2000. - Vol. 62, Is. 3. - P2181-2184. - ISSN 0163-1829, DOI 10.1103/PhysRevB.62.2181
Примечания : Cited References: 24
Предметные рубрики: SPIN
EXCITATIONS
MEDIA
Аннотация: To describe a multilayer structure with arbitrary thicknesses of the interfaces between layers, we introduce a model in which the dependence of a material parameter along the axis of such a superlattice is described by a Jacobian elliptic sine function. Depending on the value of the modulus kappa of the elliptic function, the model describes the limiting cases of multilayers with sharp interfaces (kappa=1, d/l=0, where d is the thickness of the interface, l is the period of the superlattice) and of sinusoidal superlattices (kappa=0, d/l=1/4), as Well as all intermediate situations. We investigate the wave spectrum in such a superlattice. The dependences of the widths of the gaps in the spectrum at the boundaries of ail odd Brillouin zones on the ratio d/l are found. It is shown that the thicknesses of the interfaces can be determined if the experimental value of the relation between the widths of the first gap Delta v(1) and any other gap Delta v(n) is known.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Fedorov A. S., Orlov Yu. S., Solovyov L. A., Vereshchagin S. N., Gavrilkin, S. Yu, Tsvetkov, A. Yu, Gorev M. V., Novikov, S., V, Ovchinnikov S. G.
Заглавие : Thermoelectric properties of the SmCoO3 and NdCoO3 cobalt oxides
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [16-13-00060]
Место публикации : Ceram. Int. - 2020. - Vol. 46, Is. 11. - P.17987-17991. - ISSN 0272-8842, DOI 10.1016/j.ceramint.2020.04.113. - ISSN 1873-3956(eISSN)
Примечания : Cited References: 41. - This study was supported by the Russian Science Foundation, project no. 16-13-00060.
Предметные рубрики: MAGNETIC-PROPERTIES
SPIN
CONDUCTIVITY
TRANSITIONS
LACOO3
SITE
Аннотация: The thermoelectric properties of the NdCoO3 and SmCoO3 rare-earth cobalt oxides with a perovskite structure have been investigated in a wide temperature range. It is shown that, in the low-temperature region, the thermal conductivity of the compounds has a sharp maximum and the electrical conductivity of the samples increases with temperature, whereas the Seebeck coefficient behaves nonmonotonically with increasing temperature. The SmCoO3 oxide is characterized by the positive thermopower over the entire investigated range with a sharp growth in the low-temperature region, attaining the maximum value (S ≈ 1000 μV/K) near room temperature, and a further decrease. It has been established that, in the NdCoO3 oxide, the Seebeck coefficient changes its sign, which was rarely observed in the La-based compounds and is atypical of the undoped rare-earth cobalt oxides. The thermopower maximum obtained at a temperature of 450 K is 400 μV/K. The regions of the fastest growth of the thermoelectric power factor correspond to the anomalies caused by the spin transition of Со3+ ions and the dielectric–metal transition.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Dudnikov V. A., Gorev M. V., Vereshchagin S. N., Solov’ev L. A., Ovchinnikov S. G.
Заглавие : Thermal properties of rare earth cobalt oxides and of La1–xGdxCoO3 solid solutions
Место публикации : JETP Letters. - 2016. - Vol. 103, Is. 9. - P.607-612. - ISSN 00213640 (ISSN), DOI 10.1134/S0021364016090058
Примечания : Cited References: 21. - This work was supported by the Russian Foundation for Basic Research, project nos. 16-02-00507 and 16-02-00098, and by the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools, project no. SP-1844.2016.1. The X-ray diffraction analysis of the crystal structure and the measurement of specific heat were supported by the Siberian Branch, Russian Academy of Sciences (project no. V.45.3.1).
Предметные рубрики: PROFILE REFINEMENT
SPIN
CRYSTALS
Аннотация: Powder X-ray diffraction data for the crystal structure, phase composition, and molar specific heat for La1‒xGdxCoO3 cobaltites in the temperature range of 300–1000 K have been analyzed. The behavior of the volume thermal expansion coefficient in cobaltites with isovalent doping in the temperature range of 100–1000 K is studied. It is found that the β(T) curve exhibits two peaks at some doping levels. The rate of the change in the occupation number for the high-spin state of cobalt ions is calculated for the compounds under study taking into account the spin–orbit interaction. With the Birch–Murnaghan equation of state, it is demonstrated that the low-temperature peak in the thermal expansion shifts with the growth of the pressure toward higher temperatures and at pressure P ∼ 7 GPa coincides with the second peak. The similarity in the behavior of the thermal expansion coefficient in the La1–xGdxCoO3 compounds with the isovalent substitution and the undoped LnCoO3 compound (Ln is a lanthanide) is considered. For the whole series of rare earth cobalt oxides, the nature of two specific features in the temperature dependence of the specific heat and thermal expansion is revealed and their relation to the occupation number for the high-spin state of cobalt ions and to the insulator–metal transition is established.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Mitskan V. A., Petrakovskii G. A.
Заглавие : The magnetoelastic mechanism of singlet phase formation in a two-dimensional quantum antiferromagnet
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 102, Is. 2. - P234-247. - ISSN 1063-7761, DOI 10.1134/S106377610602004X
Примечания : Cited References: 18
Предметные рубрики: GROUND-STATE
SPIN
TRANSITION
CUGEO3
MODEL
Ключевые слова (''Своб.индексиров.''): 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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Symmetrical conical incommensurate structures of a frustrated isotropic Heisenberg ferrimagnet
Место публикации : JETP Letters. - 2015. - Vol. 102, Is. 2. - P.100-104. - ISSN 0021, DOI 10.1134/S0021364015140076. - ISSN 10906487(eISSN)
Примечания : Cited References:16
Предметные рубрики: CLASSICAL-THEORY
SPIN
MULTIFERROICS
Аннотация: The conditions of the appearance of conical incommensurate structures have been studied analytically for a ferrimagnet with the geometrically frustrated exchange between spins in different magnetic positions (subsystems) and the competition between exchanges in one of the subsystems. The phase transition temperatures to the conical states have been determined. The types of phase transitions have been determined by the numerical minimization of the free energy and (temperature-exchange parameters) phase diagrams have been obtained.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Shauro V. P.
Заглавие : Selective control of the states of multilevel quantum systems using nonselective rotation operators
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 108, Is. 1. - P5-17. - ISSN 1063-7761, DOI 10.1134/S1063776109010026
Примечания : Cited References: 20
Предметные рубрики: FOURIER-TRANSFORM
SPIN
Ключевые слова (''Своб.индексиров.''): quantum electronics--quantum optics--quadrupole nucleus--quantum systems--radio frequencies--rf fields--rf pulse--selective controls--selective pulse--rotation
Аннотация: We have calculated the sequences of nonselective rotation operators separated by intervals of free evolution that perform selective rotations between adjacent levels in systems with three, four, five, and six nonequidistant levels. We have numerically simulated the realization of the calculated sequences for quadrupole nuclei with corresponding spins controlled by intense nonselective radio-frequency (RF) pulses and investigated the dependences of the realization error on the parameters of external and internal interactions. To reduce the error when the RF field is not strong enough, we have found composite nonselective RF pulses consisting of five simple ones. We show that the error of the composite selective rotation operator can be reduced signifi- cantly in comparison to the error of a simple single selective pulse.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shorikov A., Korshunov M. M., Anisimov V. I.
Заглавие : Role of electronic correlations in the Fermi surface formation of Na (x) CoO2
Разночтения заглавия :авие SCOPUS: Role of electronic correlations in the Fermi surface formation of Na xCoO 2
Место публикации : JETP Letters. - 2011. - Vol. 93, Is. 2. - P.80-85. - ISSN 0021-3640, DOI 10.1134/S0021364011020123
Примечания : Cited References: 36. - The authors thank I. Eremin, M. Laad, and S. G. Ovchinnikov for useful discussions. A. S. and V. I. A. acknowledge the support of the Russian Foundation for Basic Research (project nos. 10-02-00046-a, 09-02-00431-a, and 10-02-00546-a), the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (project nos. NSh-1941.2008.2 and MK-3758.2010.2), the Presidium of the Russian Academy of Science (programs "Quantum Microphysics of Condensed Matter" N7 and "Strongly Compressed Materials"), and the Russian Federal Agency for Science and Innovations (project no. 02.740.11.0217). M. M. K. acknowledges the support of INTAS (YS Grant no. 05-109-4891); the Russian Foundation for Basic Research (project nos. 09-02-00127, 06-02-16100, and 06-02-90537-BNTS); the Siberian Branch, Russian Academy of Sciences (integration program no. 40); the Presidium of the Russian Academy of Sciences (program no. 5.7); the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (project no. MK-1683.2010.2); and the Ministry of Education and Science of the Russian Federation (project no. R891, federal program "Scientific and Pedagogical Personnel of Innovative Russia for 2009-2013").
Предметные рубрики: DENSITY-FUNCTIONAL CALCULATION
METALS
SPIN
Аннотация: Band structure of metallic sodium cobaltate Na (x) CoO2 (x = 0.33, 0.48, 0.61, 0.72) has been investigated by local density approximation + Hubbard U (LDA+U) method and within Gutzwiller approximation for the Co-t (2g) manifold. Correlation effects being taken into account results in suppression of the e' (g) hole pockets at the Fermi surface in agreement with recent angle-resolved photoemission spectroscopy (ARPES) experiments. In the Gutzwiller approximation the bilayer splitting is significantly reduced due to the correlation effects. The formation of high spin (HS) state in Co d-shell was shown to be very improbable.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Mitskan V. A., Zlotnikov A. O., Shustin M. S., Aksenov S. V.
Заглавие : Occurrence of Topologically Nontrivial Phases, Cascade of Quantum Transitions, and Identification of Majorana Modes in Chiral Superconductors and Nanowires (Scientific Summary)
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [16-02-00073, 18-32-00443, 19-02-00348]; Government of the Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science [18-42-243017, 18-42-243018, 18-42-240014]; Council of the President of the Russian Federation for State Support of Young Scientists and Leading Scientific SchoolsLeading Scientific Schools Program [MK-3722.2018.2, MK-3594.2018.2]
Место публикации : JETP Letters. - 2019. - Vol. 110, Is. 2. - P.140-153. - ISSN 0021-3640, DOI 10.1134/S002136401914011X. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 88. - This work was supported by the Russian Foundation for Basic Research (project nos. 16-02-00073, 18-32-00443, 19-02-00348) and jointly by the Government of the Krasnoyarsk Territory, the Krasnoyarsk Regional Fund of Science (project no. 18-42-243017, "Manifestation of Coulomb Interactions and Effects of Bounded Geometry in the Properties of Topological Edge States of Nanostructures with Spin-Orbit Interaction"; project no. 18-42-243018, "Contact Phenomena and Magnetic Disorder in the Problem of the Formation and Detection of Topologically Protected Edge States in Semiconductor Nanostructures"; and project no. 18-42-240014, "Single-Orbit Effective Model of an Ensemble of Spin-Polaron Quasiparticles in the Problem of Describing the Intermediate State and Pseudogap Behavior of Cuprate Superconductors"). S.V. Aksenov and A. O. Zlotnikov acknowledge the support of the Council of the President of the Russian Federation for State Support of Young Scientists and Leading Scientific Schools (project nos. MK-3722.2018.2 and MK-3594.2018.2).
Предметные рубрики: HUBBARD FERMIONS
BOUND-STATE
SPIN
POLARIZATION
COEXISTENCE
Аннотация: The problems of occurrence and experimental identification of topologically nontrivial phases in condensed matter have been reviewed. The results of the study of the effect of strong intra- and interatomic Coulomb interaction on a quantum phase transition with change in the topological index in an ensemble of Hubbard fermions on a triangular lattice have been reported. Nontrivial topology of the phase of coexistence of d + id chiral superconductivity and 120° spin ordering in a system with the triangular lattice has been discussed and the formation of Majorana modes in such a phase has been demonstrated. A cascade of quantum transitions that occurs at the variation of the magnetic field or the electrochemical potential has been analyzed for an open nanowire with the Rashba spin-orbit coupling and the induced superconducting pairing potential. It has been shown that anomalies of magneto- and electrocaloric effects are manifested near such quantum transitions and can be used to experimentally test materials on the existence of topologically nontrivial phases in them. The switching of the spin-polarized current in the topological superconducting phase has been predicted for a semimetal/superconducting wire/semimetal structure in the weak nonequilibrium regime.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : GEKHT R. S.
Заглавие : MAGNETIC-STRUCTURES AND PROPERTIES OF STATES IN STRONGLY FRUSTRATED HEISENBERG ANTIFERROMAGNETS
Место публикации : Zhurnal Eksperimentalnoi Teor. Fiz.: MEZHDUNARODNAYA KNIGA, 1992. - Vol. 102, Is. 6. - P1968-1982. - ISSN 0044-4510
Примечания : Cited References: 23
Предметные рубрики: PHASE-TRANSITIONS
SPIN
LATTICE
MODELS
LONG
Аннотация: The magnetic structures and properties of states in frustrated Heisenberg antiferromagnets are analyzed. It is shown that frustrations induced due to additional spins in the system lead to a large variety of phase with the commensurable and uncommensurable periods and also to arising nonperiodical phases. The energy spectrum of states is studied. It is found that in the large region of the frustration parameter variation the modulated phase (0, Q) is unstable. The phase diagram of states is found and the region of local degeneration for some structures is indicated.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Tarasov A. S., Rautskii M. V., Lukyanenko A. V., Varnakov S. N., Ovchinnikov S. G.
Заглавие : Magnetic-field-driven electron transport in ferromagnetic/ insulator/ semiconductor hybrid structures
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН , Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-42-242036, 16-42-243046]; Russian Ministry of Education and Science [16.663.2014K]
Место публикации : J. Magn. Magn. Mater.: Elsevier Science, 2017. - Vol. 440: EURO-Asian Symposium on Trends in Magnetism (EASTMAG) (AUG 15-19, 2016, Siberian Fed Univ, Krasnoyarsk, RUSSIA). - P.140-143. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2016.12.092. - ISSN 1873-4766(eISSN)
Примечания : Cited References:27. - This study was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund, Project nos. 16-42-242036 and 16-42-243046, the Russian Ministry of Education and Science, state assignment no. 16.663.2014K.
Предметные рубрики: SPINTRONICS
BREAKDOWN
SILICON
SPIN
Ключевые слова (''Своб.индексиров.''): hybrid structures--magnetoresistance--magnetoimpedance--photovoltage
Аннотация: Extremely large magnetotransport phenomena were found in the simple devices fabricated on base of the Me/SiO2/p-Si hybrid structures (where Me are Mn and Fe). These effects include gigantic magnetoimpedance (MI), dc magnetoresistance (MR) and the lateral magneto-photo-voltaic effect (LMPE). The MI and MR values exceed 10(6)% in magnetic field about 0.2 T for Mn/SiO2/p-Si Schottky diode. LMPE observed in Fe/SiO2/p-Si lateral device reaches the value of 10(4)% in a field of 1 T. We believe that in case with the Schottky diode MR and MI effects are originate from magnetic field influence on impact ionization process by two different ways. First, the trajectory of the electron is deflected by a magnetic field, which suppresses acquisition of kinetic energy and therefore impact ionization. Second, the magnetic field gives rise to shift of the acceptor energy levels in silicon to a higher energy. As a result, the activation energy for impact ionization significantly increases and consequently threshold voltage rises. Moreover, the second mechanism (acceptor level energy shifting in magnetic field) can be responsible for giant LMPE.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Edel'man I. S., Khudyakov A. E., Zabluda V. N., Markov V. V., Romanova O. B.
Заглавие : Magnetic ordering of Dy in NiFe-Dy bilayer films
Место публикации : JETP Letters. - 1998. - Vol. 67, Is. 5. - P.339-342. - ISSN 0021-3640, DOI 10.1134/1.567670
Примечания : Cited References: 8
Предметные рубрики: SPIN
Аннотация: The first results of measurements of the temperature and spectral dependences of the circular magnetic dichroism in NiFe-Dy bilayer films are reported. These results show that even at room temperature Dy in such systems is ordered ferromagnetically to a large depth (similar to 600 Angstrom). (C) 1998 American Institute of Physics. [S0021-3640(98)00705-1].
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gekht R. S., Bondarenko I. N.
Заглавие : Magnetic ordering and phase transitions in planar antiferromagnetic systems with a Kagome lattice
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 1998. - Vol. 86, Is. 6. - P1209-1215. - ISSN 1063-7761, DOI 10.1134/1.558592
Примечания : Cited References: 23
Предметные рубрики: TRIANGULAR LATTICE
2 DIMENSIONS
SPIN
MODEL
Аннотация: We study the process of magnetic ordering in planar antiferromagnetic systems with a Kagome lattice. It is found that if the interaction between next-nearest-neighbor spins is taken into account, the heat capacity of such systems has a singularity at a finite temperature T. On the basis of a scaling analysis of finite-size systems we study the behavior of thermodynamic quantities in the neighborhood of a phase transition. We find that the phase transition at the critical point is due to discrete- and continuous-symmetry breaking, in which the long-range chiral order and the power-law translational spin order emerge simultaneously. Finally, we calculate the temperatures of the transition to different (with three and nine spins per unit cell) ordered states. (C) 1998 American Institute of Physics.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Ovchinnikov S. G., Balaev A. D., Ivanova N.B., Pashkevich, Yu. G., Michel C.R., Bondarenko G. V.
Заглавие : Magnetic and transport properties of Gd(0.9)A(0.1)CoO(3-delta) (A = Ba, Sr)
Место публикации : J. Magn. Magn. Mater. - 2009. - Vol. 321, Is. 9. - P.1266-1271. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2008.11.087
Примечания : Cited Reference Count: 31. - Гранты: This study was supported by the Rosnauka (Project no. MK-4278.2008.2), Russian Foundation for Basic Research (Project no. 08-02-90708 mob_st) and "Strongly correlated electrons'' program of the Department of Physical Sciences of RAS.Финансирующая организация: Rosnauka [MK-4278.2008.2]; Russian Foundation for Basic Research [08-02-90708 mob_st]; "Strongly correlated electrons'' program of the Department of Physical Sciences of RAS
Предметные рубрики: PEROVSKITE
PR
LA
EU
ND
LN
TRANSITION
SPIN
GD
SM
Ключевые слова (''Своб.индексиров.''): perovskite structure--doped cobaltite--magnetic susceptibility--metal-insulator transition--doped cobaltite--magnetic susceptibility--metal-insulator transition--perovskite structure--antiferromagnetism--barium--cobalt compounds--electric conductivity--ferromagnetic materials--ferromagnetism--gadolinium--magnetic susceptibility--metal insulator boundaries--oxide minerals--paramagnetic materials--perovskite--phase separation--semiconductor insulator boundaries--transport properties--antiferromagnetic--doped cobaltite--doped samples--electrical conductivity measurements--ferromagnetic transitions--insulator-metal transitions--magnetic and transport properties--magnetic behaviors--perovskite structure--temperature ranges--transport datum--x- ray diffractions--metal insulator transition
Аннотация: The X-ray diffraction, magnetization and electrical conductivity measurements for Gd(0.9)A(0.1)CoO(3-delta) (A = Ba, Sr) have been made. The complicated magnetic behavior, including the paramagnetic-ferromagnetic-antiferromagnetic and paramagnetic-ferromagnetic transitions, was found for Ba- and Sr-doped samples. The gradual insulator-metal transitions were observed in a wide temperature range T = 600-800 K. The complex magnetic and transport data could be explained on the basis of the structural phase separation. (C) 2009 Elsevier B.V. All rights reserved.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dzebisashvili D. M., Klyuchantsev, Andrey B.
Заглавие : London Penetration Depth as a Test of Order Parameter Symmetry in Sodium Cobaltate Superconductors
Коллективы : Russian Foundation for Basic Research (RFBR) [18-02-00837]; Presidium of the Russian Academy of Sciences [12]
Место публикации : Symmetry-Basel. - 2019. - Vol. 11, Is. 5. - Ст.633. - ISSN 2073-8994, DOI 10.3390/sym11050633
Примечания : Cited References: 43. - The work was financially supported by the Russian Foundation for Basic Research (RFBR) (project no. 18-02-00837) and by the program of the Presidium of the Russian Academy of Sciences No. 12 "Fundamental problems of high-temperature superconductivity".
Предметные рубрики: SPIN
DEPENDENCE
POWDER
CHARGE
PHASE
GAP
Аннотация: Temperature dependence of the magnetic field penetration depth λ was calculated for water intercalated sodium cobaltate superconductor NaxCoO2⋅yH2O. Assuming that the system is in the chiral d+id–wave superconducting state, it was shown that the shifting of the excitation spectrum nodal points off the normal phase Fermi surface due to variation of the sodium content x changes the functional form of the temperature dependence of λ−2 from exponential to linear in the low temperatures region. It is argued that this change in the functional form of T–dependence of the λ−2 can serve as a proof for the chiral symmetry of the superconducting order parameter in the sodium cobaltate.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Val'kova T. A., Mitskan V. A.
Заглавие : Gapless chiral superconducting (d + id)-wave phase in strongly correlated layered material with a triangular lattice
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [19-02-00348, 18-42240014]; Krasnoyarsk Kray Science Foundation [18-42-240014]; Administration of the Krasnoyarsk Kray
Место публикации : J. Exp. Theor. Phys. - 2020. - Vol. 130, Is. 2. - P.235-246. - ISSN 1063-7761, DOI 10.1134/S1063776120010197. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 44. - This study was supported by the Russian Foundation for Basic Research (project nos. 19-02-00348 and 18-42240014), the Administration of the Krasnoyarsk Kray, the Krasnoyarsk Kray Science Foundation within research project "Single-orbital Effective Model of Ensemble of Spin-Polaron Quasiparticles in the Problem of Description of the Intermediate State and Pseudogap Behavior of Cuprate Superconductors" (project no. 18-42-240014).
Предметные рубрики: TRANSITIONS
SPIN
Аннотация: It is shown that interlayer electron tunneling in the quasi-two-dimensional ensemble of Hubbard fermions leads to the realization of the gapless superconducting phase with the chiral (d + id)-wave order parameter symmetry, not for a single value of sodium ion concentration, but in a wide range of concentrations. Precisely this situation corresponds to experimental data on the layered sodium cobaltite intercalated by water (NaxCoO2 · yH2O). Intra-atomic electron repulsion that determines the strong electron correlation regime leads to the representation of Hubbard fermions, the interaction of which ensures Cooper instability. Intersite intralayer interactions between fermions considerably affect the positions of nodal points of the chiral order parameter and change the critical concentration at which a topological transition occurs in the 2D system of Hubbard fermions.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Polukhin D. S.
Заглавие : Fine structure of the crossing resonance spectrum of wavefields in an inhomogeneous medium
Место публикации : J. Exp. Theor. Phys. - 2020. - Vol. 130, Is. 3. - P.358-369. - ISSN 1063-7761, DOI 10.1134/S1063776120010033. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 37
Предметные рубрики: SUPERCONDUCTING CRITICAL-TEMPERATURE
ELECTRON
BREAKDOWN
SPIN
Аннотация: The crossing resonance of two wavefields m(x, t) and u(x, t) of different natures in an inhomogeneous medium with zero mean value of the coupling parameter η between fields has been studied. The stages of formation of the fine structure of the crossing resonance have been analyzed. It has been shown within the model of independent crystallites that the removal of the degeneracy of eigenfrequencies of these fields at the crossing resonance point has a threshold character in the coupling parameter and occurs under the condition η ηc, where ηc = |Γu – Γm|/2, Γu and Γm are the relaxation parameters of the corresponding wavefields. At η ηc, each random implementation of the Green’s functions G~′′mm and G~′′uu of wavefields has the form of two resonance peaks with the same half-width (Γu + Γm)/2 spaced by the interval 2η; this form is standard for crossing resonances. At η ηc, the functions G~′′mm and G~′′uu are different: if Γu Γm, the function G~′′mm has the form of a narrow resonance peak at ω = ωr, whereas the function G~′′uu has the form of a broader resonance peak split at the top by a narrow antiresonance. Averaging over regions where η ηc leads to the formation of a broad resonance with a resonance line half-width of about η2〉1/2 on the both averaged Green’s functions, which is due to the stochastic distribution of resonance frequencies. Averaging over regions where η ηc results in the sharpening of a resonance peak on the function G′′mm and an antiresonance peak on the function G′′uu at the same frequency ω vu at the first and second crossing points, respectively.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Troyanchuk I. O., Bushinsky M. V., Tereshko N. V., Lanovsky R. A., Sikolenko V. V., Ritter C., Orlov Yu. S., Ovchinnikov S. G.
Заглавие : Ferromagnet-antiferromagnet transition in layered perovskites of Sr3YCo4O10.5 type
Коллективы : Belarussian Foundation for Basic Research [F18R-159]; Russian Foundation Basic Research [18-52-00017 Bel_a, 16-02-00507, 18-52-00020]; Council on grants of the President of the Russian Federation [SP-1844.2016.1]
Место публикации : Mater. Res. Express. - 2019. - Vol. 6, Is. 2. - Ст.026105. - ISSN 2053-1591, DOI 10.1088/2053-1591/aaef21
Примечания : Cited References: 30. - This work was supported by the Belarussian Foundation for Basic Research (project F18R-159) and Russian Foundation Basic Research (contract no. 18-52-00020). Yu S Orlov and SG Ovchinnikov are grateful Russian Foundation Basic Research (contracts no. 18-52-00017 Bel_a, 16-02-00507) and Council on grants of the President of the Russian Federation (SP-1844.2016.1) for the support.
Предметные рубрики: SPIN
NANOWIRES
Ключевые слова (''Своб.индексиров.''): neutron diffraction--orbital ordering--spin state
Аннотация: Sr1−xYxCoO2.65 (x = 0.2) with layered perovskite structure was studied by neutron diffraction, synchrotron x-ray and magnetometry methods. It is shown that in the 90–375 K temperature range the crystal structure can be described by the monoclinic space group A2/m with the superstructure 4√2a p × 2√2a p × 4a p (with a p corresponding to the unit cell parameter of the primitive cell) while basic diffraction peaks are well indexed in the space group I4/mmm (2a p × 2a p × 4a p ) shows an almost standard magnetization. The basic magnetic structure is G-type antiferromagnetic with average magnetic moments of 2.7 μ B/Co and 1.7 μ B/Co in anion-deficient CoO4+γ and stoichiometric CoO6 layers, respectively. A ferromagnetic component of about 0.27 μ B/Co is determined from the magnetization measurements at 8 K. Sr0.8Y0.2CoO2.65 shows an almost standard magnetization versus temperature dependence whereas Sr0.75Y0.25CoO2.65 exhibits an antiferromagnet-ferromagnet transition accompanied by a structural transformation. There is practically no spontaneous magnetization in x = 0.3. The type of the magnetic structure and the high value of TN suggest that the Co3+ ions are in both structural layers predominantly in the low-spin (LS)/high-spin (HS) state mixture. It is proposed that the ferromagnetic component is due to the orbital ordering occurring at TN in the CoO5 pyramids and the concomitant appearance of ferromagnetic coupling between the Co3+(HS) ions located in these CoO5 pyramids in the anion-deficient CoO4+γ layer.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Orlov Yu. S., Gavrilkin S. Yu., Gorev M. V., Vereshchagin S. N., Solovyov L. A., Perov N. S., Ovchinnikov S. G.
Заглавие : Effect of Gd and Sr ordering in a sites of doped Gd0.2Sr0.8CoO3-δ perovskite on its structural, magnetic, and thermodynamic properties
Место публикации : J. Phys. Chem. C: American Chemical Society, 2016. - Vol. 120, Is. 25. - P,13443-13449. - ISSN 19327447 (ISSN), DOI 10.1021/acs.jpcc.6b04810
Примечания : Cited References: 45. - The authors are thankful to the Russian Science Foundation (Project No. 16-13-00060) for financial support. The magnetic measurements were carried out in the Shared Facility Centre of P. N. Lebedev Physical Institute of RAS.
Предметные рубрики: Ln1-xSrxCoO(3-δ) Ln
PROFILE REFINEMENT
CRYSTAL-STRUCTURE
OXYGEN-CONTENT
COBALTITES
OXIDE
La1-xSrxCoO3-δ
Dy3+
SPIN
Ho3+
Аннотация: Magnetic and thermodynamic properties of perovskite Gd0.2Sr0.8CoO3−δ, with ordered and disordered states of Gd and Sr in the A-sites of the crystal lattice have been studied revealing remarkable differences in the physical properties of the ordered and disordered states. The ordered samples have larger oxygen nonstoichiometry, heat capacity, and thermal expansion anomalies, and abnormal temperature dependence of the magnetization around 350 K.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min E. V., Ovchinnikov S. G., Singh D. J.
Заглавие : Effect of frustrations on magnetism in the Ru double perovskite Sr2YRuO6
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2003. - Vol. 68, Is. 2. - Ст.24409. - ISSN 1098-0121, DOI 10.1103/PhysRevB.68.024409
Примечания : Cited References: 24
Предметные рубрики: MOTT TRANSITION
LATTICE
SPIN
ANTIFERROMAGNETISM
SUPERCONDUCTIVITY
FERROMAGNETISM
Аннотация: Localized Ru5+ spins in Sr2YRuO6 form a fcc lattice with an antiferromagnetic (AFM) nearest-neighbor (NN) coupling J approximate to 25 meV and rather low Neel temperature T-N= 26 K. Analysis of the electronic structure of Sr2RuO4 results in the effective Heisenberg model. We have studied the effect of frustrations on the AFM type-I structure of Sr2YRuO6 in the spin-wave approximation. In the model with only NN coupling the AFM state is unstable due to frustrations, and T-N = 0. Stabilization of the AFM state occurs due to the next-nearest-neighbor coupling I or due to the magnetic anisotropy D. Very small values D/J similar to I/J less than or equal to 10(-3) are enough to obtain the experimental values of T-N and sublattice magnetization m = 1.85 mu(B) /Ru (62% from the nominal S = 3/2 value).
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Platunov M. S., Dudnikov V. A., Orlov Yu. S., Kazak N. V., Solovyov L. A., Zubavichus Y. V., Veligzhanin A. A., Dorovatovskii P. V., Vereshchagin S. N., Shaykhutdinov K. A., Ovchinnikov S. G.
Заглавие : Crystal structure and electronic states of Co and Gd ions in a Gd0.4Sr0.6CoO2.85 single crystal
Коллективы : Russian Foundation for Basic Research [13-02-00958, 13-02-00358, 14-02-31051, 16-32-60049]; Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools [SP-938.2015.5]; program "UMNIK"; Siberian Branch, Russian Academy of Sciences [V.45.3.1]
Место публикации : JETP Letters. - 2016. - Vol. 103, Is. 3. - P.196-200. - ISSN 0021-3640, DOI 10.1134/S0021364016030139. - ISSN 1090-6487(eISSN)
Примечания : Cited References:20. - This work was supported in part by the Russian Foundation for Basic Research (project nos. 13-02-00958, 13-02-00358, 14-02-31051, and 16-32-60049), by the Council of the President of the Russian Federation for Support of Young Scientists and Leading Scientific Schools (project no. SP-938.2015.5), and by the program "UMNIK." The X-ray diffraction and thermochemical studies were supported by the Siberian Branch, Russian Academy of Sciences (project no. V.45.3.1).
Предметные рубрики: X-RAY-ABSORPTION
PROFILE REFINEMENT
PEROVSKITE
CHARGE
SPIN
Аннотация: X-ray diffraction and X-ray absorption near edge structure (XANES) spectra have been measured at the Со K-edge and Gd L3-edge in GdCoO3 and Gd0.4Sr0.6CoO2.85 cobaltites. The effect of Sr substitution on the crystal structure and electronic and magnetic states of Co3+ ions in a Gd0.4Sr0.6CoO2.85 single crystal has been analyzed. The XANES measurements at the Co K-edge have not showed a noticeable shift of the absorption edge with an increase in the concentration of Sr. This indicates that the effective valence of cobalt does not change. An increase in the intensity of absorption at the Gd L3-edge is due to an increase in the degree of hybridization of the Gd(5d) and O(2p) states. The effect of hole doping on the magnetic properties results in the appearance of the ferromagnetic component and in a significant increase in the magnetic moment.
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