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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nemtsev A. V., Zhandun V. S., Zinenko V. I.
Заглавие : Ab initio study of the polarization, electronic, magnetic, and optical properties of perovskite SrMO3 (M = Fe, Mn) crystals and thin films containing magnetic ions
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 126, Is. 4. - P.497-505. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776118030056
Примечания : Cited References: 30
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--density functional theory--electronic properties--iron compounds--manganese compounds--optical properties--perovskite--perovskite solar cells--polarization--strontium compounds
Аннотация: The magnetic, electronic, and polarization properties of the SrFeO3 and SrMnO3 compounds with a perovskite structure are calculated using the density functional theory in the bulk and thin-film states. A ferroelectric instability is found to be absent in the bulk state, and the polar mode is softened in the thin-film state of SrMnO3 in the presence of tensile stresses in the substrate. As a result, a polar phase with a polarization of 23 μC/cm2 appears, which agrees with experimental data. The study of the magnetic and electronic properties demonstrates the existence of G-type antiferromagnetic ordering in SrMnO3 and the appearance of a dielectric gap of about 1.5 eV in its thin film. A ferromagnetic phase with metallic conduction in both the bulk and thin-film states is detected in SrFeO3.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Anomalies in the characteristics of electronic structure upon a quantum phase transition to a state with two order parameters and the breaking of time-reversal symmetry
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 6. - P.616-619. - ISSN 10628738 (ISSN), DOI 10.3103/S106287381606040X
Примечания : Cited References: 9
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--electronic structure--phase transitions--temperature distribution--antiferromagnetic order parameter--density of state--landau expansion--periodic anderson model--quantum phase transitions--temperature dependence--time reversal symmetries--two order parameters--quantum theory
Аннотация: Based on the periodic Anderson model, microscopic expressions for the Ginzburg–Landau expansion coefficients in a phase with superconducting and antiferromagnetic order parameters are obtained. Temperature dependences of the order parameters near the temperature of the transition to this phase are established. The emergence of anomalous properties upon the quantum phase transition to the phase with two order parameters is investigated. This transition is accompanied by drastic reconstruction of the density of states, reflected by the interplay between superconductivity and antiferromagnetism. © 2016, Allerton Press, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Anomalous Properties and Coexistence of Antiferromagnetism and Superconductivity near a Quantum Critical Point in Rare-Earth Intermetallides
Место публикации : J. Experim. Theor. Phys. - 2013. - Vol. 116, Is. 5. - P.817–822. - DOI 10.1134/S1063776113050129
Аннотация: Mechanisms of the appearance of anomalous properties experimentally observed at the transition through the quantum critical point in rare-earth intermetallides have been studied. Quantum phase transitions are induced by the external pressure and are manifested as the destruction of the long-range antiferromagnetic order at zero temperature. The suppression of the long-range order is accompanied by an increase in the area of the Fermi surface, and the effective electron mass is strongly renormalized near the quantum critical point. It has been shown that such a renormalization is due to the reconstruction of the quasiparticle band, which is responsible for the formation of heavy fermions. It has been established that these features hold when the coexistence phase of antiferromagnetism and superconductivity is implemented near the quantum critical point.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'menko A. M., Mukhin A. A., Ivanov V. Y., Kadomtseva A. M., Lebedev S. P., Bezmaternykh L. N.
Заглавие : Antiferromagnetic Resonance and Dielectric Properties of Rare-earth Ferroborates in the Submillimeter Frequency Range
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 1. - P113-120. - ISSN 1063-7761, DOI 10.1134/S106377611105013X
Примечания : Cited References: 27. - This work was supported by the Russian Foundation for Basic Research, project no. 10-02-00846.
Предметные рубрики: GDFE3(BO3)(4)
SPECTROSCOPY
CRYSTAL
Ключевые слова (''Своб.индексиров.''): antiferromagnetic resonance--basic parameters--effective anisotropy constant--ferroborates--ferroics--ferromagnetic orderings--frequency ranges--magnetic interactions--magnetoresonance--millimeter frequency range--rare earth ions--submillimeters--antiferromagnetic materials--crystallography--erbium--europium--ferromagnetic resonance--ion exchange--magnetic anisotropy--magnetic devices--magnetic structure--permittivity--resonance--antiferromagnetism
Аннотация: The magnetoresonance and dielectric properties of a number of crystals of a new family of multiferroics, namely, rare-earth ferroborates RFe(3)(BO(3))(4) (R = Y, Eu, Pr, Tb, Tb(0.25)Er(0.75)), are studied in the submillimeter frequency range (nu = 3-20 cm(-1)). Ferroborates with R = Y, Tb, and Eu exhibit permittivity jumps at temperatures of 375, 198, and 58 K, respectively, which are caused by the R32 - P3(1)2(1) phase transition. Antiferromagnetic resonance (AFMR) modes in the subsystem of Fe(3+) ions are detected in the range of antiferromagnetic ordering (T T(N)
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pankrats A. I., Petrakovskii G. A., Bezmaternykh L. N., Bayukov O. A.
Заглавие : Antiferromagnetic resonance and phase diagrams of gadolinium ferroborate GdFe3(BO3)(4)
Разночтения заглавия :авие SCOPUS: Antiferromagnetic resonance and phase diagrams of gadolinium ferroborate GdFe3(BO3)4
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 99, Is. 4. - P766-775. - ISSN 1063-7761, DOI 10.1134/1.1826168
Примечания : Cited References: 16
Ключевые слова (''Своб.индексиров.''): anisotropy--antiferromagnetic materials--antiferromagnetism--phase diagrams--resonance--single crystals--antiferromagnetic resonance--antiferromagnets--crystal axis--transition fields--gadolinium compounds
Аннотация: Antiferromagnetic resonance in single crystals of rhombohedral gadolinium ferroborate GdFe3(BO3)(4) was studied. The frequency-field dependences of antiferromagnetic resonance over the frequency range 26-70 GHz and the temperature dependences of resonance parameters for magnetic fields oriented along the crystal axis and in the basal plane were determined. It was found that the iron subsystem, which can be treated as a two-sublattice antiferromagnet with anisotropy of the easy-plane type, experienced ordering at T = 38 K. At temperatures below 20 K, the gadolinium subsystem with the opposite anisotropy sign strongly influenced the anisotropic properties of the crystal. This resulted in a spontaneous spin-reorientation transition from the easy-plane to the easy-axis state at 10 K. Below 10 K, magnetic field-induced transitions between the states were observed. Experimental phase diagrams on the temperature-magnetic field plane were constructed for fields oriented along the crystal axis and in the basal plane. A simple model was used to calculate the critical transition fields. The results were in close agreement with the experimental values measured at T = 4.2 K for both field orientations. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Belskaya N. A., Moshkina E. M., Bezmaternykh L. N., Vasiliev A. D., Sofronova S. N., Eremina R. M., Eremin E. V., Muftakhutdinov A. R., Cherosov M. A., Ovchinnikov S. G.
Заглавие : Antiferromagnetism of the cation-ordered warwickite system Mn2-xMgxBO4 (x=0.5, 0.6 and 0.7)
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [20-02-00559]; Government of Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science to the research project [18-42243007]
Место публикации : J. Magn. Magn. Mater. - 2020. - Vol. 507. - Ст.166820. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2020.166820. - ISSN 1873-4766(eISSN)
Примечания : Cited References: 39. - The reported study was funded by the Russian Foundation for Basic Research (no. 20-02-00559), Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project. 18-42243007.
Предметные рубрики: SPIN-GLASS BEHAVIOR
CRYSTAL-STRUCTURES
SINGLE-CRYSTALS
INSIGHTS
MGFEBO4
Аннотация: X-ray diffraction, heat capacity and magnetic measurements are performed on single crystals of Mn2-xMgxBO4 (x = 0.5, 0.6 and 0.7) with the warwickite structure. The monoclinic symmetry is found for all samples with the space group P21/n. The M1 site is occupied by trivalent Mn ions while the M2 site is occupied by a mixture of divalent Mg and Mn ions. Regular cation and charge distributions are observed, which is unusual for heterometallic warwickites. The local octahedral distortions of M1O6 show the monotonic dependence on the Mg content and are in accordance with the Jahn-Teller distortion. All samples are found to undergo long-range antiferromagnetic ordering with rather low transition temperatures of TN = 16, 14 and 13 K for x = 0.5, 0.6, and 0.7, respectively. The ordering of local octahedral distortions, caused by the strong electron-phonon interaction of the trivalent Mn ions, is proposed to stabilise the cationic ordering and, as a result, the long-range magnetic ordering in the material.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Andryushin N. D., Zinenko V. I., Pavlovskii M. S., Shinkorenko A. S.
Заглавие : Calculation and Comparison of Electronic, Vibrational, Polarization, and Magnetic Properties of Double Perovskites CaMnTi2O6 and CaFeTi2O6
Место публикации : J. Exp. Theor. Phys. - 2019. - Vol. 129, Is. 6. - P.1036-1044. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776119110013
Примечания : Cited References: 18. - This work was supported by the Russian Foundation for Basic Research (project no. 18-02-00130-a)
Аннотация: Vibrational, polarization, magnetic, and electronic properties of double perovskites CaMnTi2O6 and CaFeTi2O6 with a rare type of “column” ordering of divalent metal cations have been calculated based on the density functional theory. Analysis of the crystal lattice dynamics for paraelectric phase P42/nmc of both compounds has revealed that ferroelectric instability exists only in CaMnTi2O6. It is found that the structure distortion of the paraphrase of CaMnTi2O6 in the eigenvector of the unstable polar mode leads to a structure with the P42/nmc space group. The calculated spontaneous polarization for the ferroelectric phase of CaMnTi2O6 is Ps = 25 μC/cm2. The spin-polarization calculations have shown that the ground state is ferromagnetic in the CaFeTi2O6 crystal and antiferromagnetic in the CaMnTi2O6 crystal. The exchange interaction constants have been calculated using the Heisenberg model and the mean field approximation; the phase transition temperature for each compound has been estimated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M.
Заглавие : Canted phase of an antiferromagnetic Anderson lattice
Место публикации : Physica B: ELSEVIER SCIENCE BV, 2006. - Vol. 378-80: International Conference on Strongly Correlated Electron Systems (SECES 05) (JUL 26-30, 2005, Vienna, AUSTRIA). - P692-693. - ISSN 0921-4526, DOI 10.1016/j.physb.2006.01.223
Примечания : Cited References: 5
Ключевые слова (''Своб.индексиров.''): heavy fermions--antiferromagnetic canted phase--antiferromagnetic canted phase--heavy fermions--antiferromagnetism--band structure--magnetic field effects--magnetic fields--magnetization--spectrum analysis--thermal effects--antiferromagnetic canted phase--energy spectrum--heavy fermions--quasiparticle bands--fermions
Аннотация: On the basis of extended periodic Anderson model with anti ferromagnetic (AFM) exchange and s-f exchange interactions the energy spectrum of heavy-fermion (HF) AFM metals is calculated. The quasiparticle band structure in collinear AFM phase is described by four splitted bands one of which is very narrow (order of exchange interaction constant) and lies in the vicinity of a localized level. Application of an external magnetic field causes a canting of the sublattice magnetization and due to s-f exchange interaction strongly modifies the HF band picture. Thus eight different quasiparticle bands appear. Their evolution when temperature and magnetic field change is studied. (c) 2006 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Cluster perturbation theory in Hubbard model exactly taking into account the short-range magnetic order in 2 x 2 cluster
Коллективы :
Разночтения заглавия :авие SCOPUS: Cluster perturbation theory in Hubbard model exactly taking into account the short-range magnetic order in 2 × 2 cluster
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 111, Is. 4. - P635-644. - ISSN 1063-7761, DOI 10.1134/S1063776110100146
Примечания : Cited References: 23. - The authors thank V. V. Val'kov for fruitful discussions of this work. This research was supported financially by the Russian Foundation for Basic Research (project nos. 09-02-90723-mob_st and 09-02-00127) and by program no. 5.7 of the Presidium of the Russian Academy of Sciences and integration project no. 40 of the Siberian Branch and Ural Division of the Russian Academy of Sciences.
Предметные рубрики: INFINITE DIMENSIONS
SYSTEMS
STATE
Ключевые слова (''Своб.индексиров.''): antiferromagnetic orders--characteristic energy--cluster perturbation theories--coulomb repulsions--density of state--dynamic mean field theories--eigenvalue problem--exact diagonalization--excited levels--finite temperatures--half-filling--hubbard--metal insulator transition temperature--nearest neighbors--numerical solution--pseudo-gap--quasiparticle spectrum--shadow zone--short-range magnetic orders--temperature evolution--zero temperatures--antiferromagnetism--eigenvalues and eigenfunctions--fermi level--hubbard model--mean field theory--metal insulator boundaries--perturbation techniques--semiconductor insulator boundaries--statistical mechanics--metal insulator transition
Аннотация: The cluster perturbation theory is presented in the 2D Hubbard model constructed using X operators in the Hubbard-I approximation. The short-range magnetic order is taken into account by dividing the entire lattice into individual 2 x 2 clusters and solving the eigenvalue problem in an individual cluster using exact diagonalization taking into account all excited levels. The case of half-filling taking into account jumps between nearest neighbors is considered. As a result of numerical solution, a shadow zone is discovered in the quasiparticle spectrum. It is also found that a gap in the density of states in the quasiparticle spectrum at zero temperature exists for indefinitely small values of Coulomb repulsion parameter U and increases with this parameter. It is found that the presence of this gap in the spectrum is due to the formation of a short-range antiferromagnetic order. An analysis of the temperature evolution of the density of states shows that the metal-insulator transition occurs continuously. The existence of two characteristic energy scales at finite temperatures is demonstrated, the larger scale is associated with the formation of a pseudogap in the vicinity of the Fermi level, and the smaller scale is associated with the metal-insulator transition temperature. A peak in the density of states at the Fermi level, which is predicted in the dynamic mean field theory in the vicinity of the metal-insulator transition, is not observed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Coexistence of superconductivity and antiferromagnetism in heavy-fermion intermetallic compound CeRhIn5
Место публикации : J. Supercond. Nov. Magn. - 2013. - Vol. 26, Is. 9. - P.2885-2886. - ISSN 1557-1939, DOI 10.1007/s10948-013-2222-4
Ключевые слова (''Своб.индексиров.''): coexistence superconductivity antiferromagnetism--heavy-fermion systems--periodic anderson model
Аннотация: An interference of heavy-fermion superconductivity (SC) and antiferromagnetism (AFM) has been studied in the framework of the periodic Anderson model with the superexchange interaction between localized electrons. It has been shown that pressure-induced energy change of the localized states leads to modifying antiferromagnetic and superconducting order parameters. Conditions have been found for the coexistence of SC and AFM in the model. Theoretical results of the pressure effects on the ground state character of the heavy-fermion systems are in good agreement with experimental data for a rare-earth intermetallic compound CeRhIn5. The divergence of the effective electron mass produced by suppressing the long-range antiferromagnetic order has also been analyzed in the same framework. В© 2013 Springer Science+Business Media New York.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Coexistence of superconductivity and antiferromagnetism in heavy-fermion intermetallides
Место публикации : Theor. math. phys. - 2013. - Vol. 174, Is. 3. - P.421-437. - DOI 10.1007/s11232-013-0035-z
Аннотация: Using the two-time retarded Green’s function, we study the conditions for realizing the phase of the superconductivity and antiferromagnetism coexistence in the framework of the effective Hamiltonian for the periodic Anderson model. Such a phase was experimentally observed in rare-earth intermetallides with heavy fermions under an external pressure. In the chosen model, the Cooper instability is induced in the presence of long-range antiferromagnetic ordering as a result of the combined effect of a superexchange interaction in the subsystem of localized electrons and the hybridization between two groups of electrons. Applying an external pressure induces an increase in the energy of the localized level accompanied by an abrupt destruction of the long-range antiferromagnetic ordering in a certain region of the phase diagram. The superconductivity order parameter has a maximum value at the destruction point. We show that the decrease in the antiferromagnetic-sublattice magnetization with increasing pressure leads to a significant increase in the masses of Fermi quasiparticles, and the sign of the current carriers reverses at the critical point. The obtained results qualitatively agree well with the experimental data for the heavy-fermion intermetallide CeRhIn 5 .
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golosovsky I. V., Vasilev A. I., Mukhin A. A., Ressouche E., Skumryev V., Urcelay-Olabarria I., Gudim I. A., Bezmaternykh L. N.
Заглавие : Complex magnetic order in the Nd(Tb)Fe3(BO3)4 multiferroic revealed by single-crystal neutron diffraction
Место публикации : Phys. Rev. B. - 2019. - Vol. 99, Is. 13. - Ст.134439. - ISSN 24699950 (ISSN) , DOI 10.1103/PhysRevB.99.134439
Примечания : Cited References: 33. - This work was supported by the Russian Grant No. RFBR 16-02-00058. A.A.M. acknowledges the financial support from the Russian Science Foundation (16-12-10531).
Аннотация: Magnetic structure of the substituted multiferroics-ferroborates Nd0.9Tb0.1Fe3(BO3)4 and Nd0.8Tb0.2Fe3(BO3)4 were determined in the framework of a self-consistent refinement of the single crystal neutron diffraction data. The small substitution of Nd for Tb leads to the reorientation of the main antiferromagnetic vector L from the basal plane towards the hexagonal axis. The reorientation takes place via an angular structure for which L does not coincide with the principal crystallographic directions and evolves with temperature due to competing magnetic anisotropies of Fe, Nd, and Tb subsystems. Our refinement at 2 K reveals the existence of distortions in the collinear antiferromagnetic Fe spin arrangement suggested before in other ferroborates. Therefore, besides the main antiferromagnetic vector L, the magnetic structure involves additional fine symmetrized combinations of spin components allowed by symmetry. They coexist with certain L components and could originate from the antisymmetric Dzyaloshinsky-Moriya Fe-Fe exchange interactions. At higher temperatures, the magnetic structure is described by the simple collinear model, where the L vector is deviated from the hexagonal plane. © 2019 American Physical Society.
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Kuzmenko A. M., Mukhin A. A., Ivanov V.Yu., Bezmaternykh L. N.
Заглавие : Coupled R and Fe magnetic excitations in RFe 3(BO 3) 4 multiferroics
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Diffusion and Defect Data Pt.B: Solid State Phenomena. - 2012. - Vol. 190. - P.269-272. - ISBN 9783037854365, DOI 10.4028/www.scientific.net/SSP.190.269
Ключевые слова (''Своб.индексиров.''): magnetic resonance--rare-earth iron borates--terahertz spectroscopy--antiferromagnetics--coupled mode--exchange coupled--frequency ranges--g factors--iron borate--magnetic excitations--multiferroics--resonance mode--strong interaction--transmission spectrums--antiferromagnetism--electron transitions--gadolinium--ions--magnetic materials--magnetic permeability--magnetic resonance--terahertz spectroscopy--neodymium
Аннотация: Various resonance modes were observed in the transmission spectra of rare-earth iron borates RFe 3(BO 3) 4 (R = Nd 3+, Sm 3+, Gd 3+) at the frequency range 100-600 GHz, which were attributed to collective magnetic excitations in the exchange coupled Fe- and R-subsystems, i.e. antiferromagnetic (Fe) resonance and electron transitions in the R-ions. Strong interaction of the Fe and R oscillations was revealed and theoretically analyzed taking into account feature of the R-ion ground state. Intensities of the coupled modes (contributions to magnetic permeability) strongly depend on a difference of Fe and R ions g-factors that allows defining the sign of the latter. In particular, an appreciable intensity of exchange (Nd) modes in NdFe 3(BO 3) 4 is caused by g Nd?,|| < 0 whereas in GdFe 3(BO 3) 4 with gGd ? gFe ? 2 the exchange (Gd) modes were hided due to compensation of Fe and Gd contributions. In SmFe 3(BO 3) 4, despite a negligible Sm g-factor, the Sm modes were clear observed due to their excitation via coupling with the Fe-subsystem. В© (2012) Trans Tech Publications.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Dzebisashvili D. M., Barabanov A. F.
Заглавие : d-Wave pairing in an ensemble of spin polaron quasiparticles in the spin-fermion model of the electronic structure of the CuO2 plane
Коллективы : Dynasty Foundation, Russian Foundation for Basic Research (Siberia) [13-02-00523,13-02-00909, 13-02-98013]
Место публикации : Phys. Lett. A: Elsevier Science, 2015. - Vol. 379, Is. 5. - P.421-426. - ISSN 0375, DOI 10.1016/j.physleta.2014.11.036. - ISSN 18732429(eISSN)
Примечания : Cited References:26. - This study was supported by the Russian Foundation for Basic Research,projects Nos. 13-02-00523, 13-02-00909 and 13-02-98013 (Siberia) and theDynasty Foundation.
Предметные рубрики: SUPERCONDUCTIVITY
ANTIFERROMAGNETISM
Ключевые слова (''Своб.индексиров.''): hight-temperature cuprate superconductors--tree-band p-d model--spin--polaron--strong electron correlations
Аннотация: It is demonstrated for the first time that the strong coupling between spin moments of copper ions and oxygen holes, which arises upon hybridization mixing of two hole subsystems in the Emery model, not only affects the formation of spin polaron quasiparticles but also ensures effective attraction between them via the exchange interaction. This results in the Cooper instability with d-wave pairing in a 2D ensemble of spin polaron quasiparticles. The T-x phase diagram obtained using this approach agrees well with the available experimental data. (C) 2014 Elsevier B.V. All rights reserved.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kulbakov A. A., Sarkar R., Janson O., Dengre S., Weinhold T., Moshkina E. M., Portnichenko P. Y., Luetkens H., Yokaichiya F., Sukhanov A. S., Eremina R. M., Schlender P., Schneidewind A., Klauss H. -H., Inosov D. S.
Заглавие : Destruction of long-range magnetic order in an external magnetic field and the associated spin dynamics in Cu2GaBO5 and Cu2AlBO5 ludwigites
Место публикации : Phys. Rev. B. - 2021. - Vol. 103, Is. 2. - Ст.024447. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.103.024447
Примечания : Cited References: 46. - We thank U. Nitzsche for technical assistance. This project was funded in part by the German Research Foundation (DFG) under Grant IN 209/9-1, via Project C03 of the Collaborative Research Center SFB 1143 (project-id 247310070) at the TU Dresden, and the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, project-id 390858490). O.J. was supported by the Leibniz Association through the Leibniz Competition
Аннотация: The quantum spin systems Cu2M′BO5 (M′=Al,Ga) with the ludwigite crystal structure consist of a structurally ordered Cu2+ sublattice in the form of three-leg ladders, interpenetrated by a structurally disordered sublattice with a statistically random site occupation by magnetic Cu2+ and nonmagnetic Ga3+ or Al3+ ions. A microscopic analysis based on density-functional-theory calculations for Cu2GaBO5 reveals a frustrated quasi-two-dimensional spin model featuring five inequivalent antiferromagnetic exchanges. A broad low-temperature 11B nuclear magnetic resonance points to a considerable spin disorder in the system. In zero magnetic field, antiferromagnetic order sets in below TN≈4.1 K and ∼2.4 K for the Ga and Al compounds, respectively. From neutron diffraction, we find that the magnetic propagation vector in Cu2GaBO5 is commensurate and lies on the Brillouin-zone boundary in the (H0L) plane, qm=(0.45,0,−0.7), corresponding to a complex noncollinear long-range ordered structure with a large magnetic unit cell. Muon spin relaxation is monotonic, consisting of a fast static component typical for complex noncollinear spin systems and a slow dynamic component originating from the relaxation on low-energy spin fluctuations. Gapless spin dynamics in the form of a diffuse quasielastic peak is also evidenced by inelastic neutron scattering. Most remarkably, application of a magnetic field above 1 T destroys the static long-range order, which is manifested in the gradual broadening of the magnetic Bragg peaks. We argue that such a crossover from a magnetically long-range ordered state to a spin-glass regime may result from orphan spins on the structurally disordered magnetic sublattice, which are polarized in magnetic field and thus act as a tuning knob for field-controlled magnetic disorder.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Kokorina E. E., Pchelkina Z. V.
Заглавие : Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: the LDA + GTB approach
Разночтения заглавия :авие SCOPUS: Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: The LDA+GTB approach
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2007. - Vol. 19, Is. 48. - Ст.486203. - ISSN 0953-8984, DOI 10.1088/0953-8984/19/48/486203
Примечания : Cited References: 36
Предметные рубрики: NARROW ENERGY BANDS
HUBBARD-MODEL
SUPERCONDUCTORS
DENSITY
TEMPERATURE
ORBITALS
WAVE
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--band structure--correlation methods--crystal structure--local density approximation--superconducting materials--electronic correlations--fermionic quasiparticles--neodymium compounds
Аннотация: In the present work we report band structure calculations for the high-temperature superconductor Nd2-xCexCuO4 in the regime of strong electronic correlations within an LDA + GTB method, which combines the local density approximation (LDA) and the generalized tight-binding method (GTB). The two mechanisms of band structure doping dependence were taken into account. Namely, the one-electron mechanism provided by the doping dependence of the crystal structure, and the many-body mechanism provided by the strong renormalization of the fermionic quasiparticles due to the large on-site Coulomb repulsion. We have shown that, in the antiferromagnetic and in the strongly correlated paramagnetic phases of the underdoped cuprates, the main contribution to the doping evolution of the band structure and Fermi surface comes from the many-body mechanism.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min V. I., Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Effect of canted antiferromagnetic order on the electronic structure in the t–J* model within the cluster perturbation theory
Место публикации : J. Exp. Theor. Phys.: Maik Nauka-Interperiodica Publishing, 2016. - Vol. 123, Is. 3. - P.511-519. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776116090065
Примечания : Cited References: 50. - We are grateful to V.V. Val’kov for stimulating discussions. This work was supported by the Russian Science Foundation (project no. 14-12-00061)
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--electronic structure--high temperature superconductors--magnetic fields--antiferromagnetic orderings--cluster perturbation theories--electron-doping--external fields--external magnetic field--non-monotonic dependence--short-range correlations--spectral weight--perturbation techniques
Аннотация: The electronic structure in the two-dimensional t–J* model with canted antiferromagnetic order in an external magnetic field has been calculated within the cluster perturbation theory. In zero external field, the evolution of the Fermi surface with n-type doping has been obtained in good agreement with experimental data on cuprate superconductors. It has been shown that the inclusion of short-range correlations can result in a nonmonotonic dependence of the spectral weight distribution at the Fermi level on the external magnetic field. In contrast to the case of electron doping, such changes in the case of hole doping can be expected at experimentally achievable fields. © 2016, Pleiades Publishing, Inc.
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18.

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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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Zlotnikov A. O.
Заглавие : Effect of pressure on antiferromagnetic and superconducting ordering in systems with heavy fermions
Коллективы : International Interdisciplinary Symposium “Ordering in Minerals and Alloys” (14th; 8 -13 Sept. 2011; Rostov-on-Don)
Место публикации : Bull. Russ. Acad. Sci.: Phys.: Allerton Press, 2012. - Vol. 76, Is. 7. - P.733-736. - ISSN 0022-2860, DOI 10.3103/S1062873812070362
Примечания : Cited References: 7. - This work was supported by the Department of Physical Sciences, Russian Academy of Sciences (the Strong Electron Correlations Program); the Russian Foundation for Basic Research, projects nos. 100200251 and 110200741; the RFBR Sibir’, project no. 110298007; and by the federal target program Scientific and Pedagogical Personnel of an Innovative Russia, 2009–2013.
Ключевые слова (''Своб.индексиров.''): antiferromagnetic orderings--antiferromagnetic orders--antiferromagnetic phasis--antiferromagnetics--cooper instability--effect of pressure--external pressures--heavy fermion--impurity level--localized state--periodic anderson model--seed energy--spin moments--superconducting ordering--superexchange interaction--superconductivity--antiferromagnetism
Аннотация: Characteristics of the superconducting and antiferromagnetic phases of heavy-fermion intermet-allides are described within a periodic Anderson model with allowance for the superexchange interaction between spin moments of the localized states. It is shown that an external pressure that changes the seed energy of an impurity level can rapidly destroy the long-range antiferromagnetic order. The development of the Cooper instability near such an order-disorder transition induces the experimentally observed state in which superconductivity coexists with the antiferromagnetic ordering. В© 2012 Allerton Press, Inc.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Korshunov M. M., Shneyder E. I.
Заглавие : Effect of short antiferromagnetic correlations on the normal and superconducting properties in copper oxides
Место публикации : Diffusion and Defect Data Pt.B: Solid State Phenomena: Trans Tech Publications Ltd, 2011. - Vol. 168-169. - С. 561-566. - ISSN 10120394 (ISSN); 9783037850213 (ISBN), DOI 10.4028/www.scientific.net/SSP.168-169.561
Ключевые слова (''Своб.индексиров.''): high temperature superconductivity--short range antiferromagnetic order--strong electron correlations--antiferromagnetic materials--antiferromagnetism--copper oxides--electron correlations--electron density measurement--antiferromagnetism--electron correlations--ab initio--antiferromagnetic correlations--cuprates--high-t--high-temperature superconductivity--hubbard--low energies--multiband model--short range antiferromagnetic order--strong electron correlations--superconducting properties--t-j models--antiferromagnetic orderings--superconductivity--copper oxides--high temperature superconductivity
Аннотация: The abnormal "normal" state and origin of high temperature superconductivity in cuprates are still not clear [1-2]. The strong electron correlations (SEC) are known to be one of the main difficulties for the theory of high- Tc cuprates. The conventional LDA (local density approximation) approach to the band structure fails in the regime of SEC. Various realistic multiband models of a CuO2 layer at low energy result in the effective Hubbard or t - J models [3-7]. The hybrid LDA+GTB scheme [8] generates the low-energy effective t - t? - t? - J* model with all parameters calculated ab initio.
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