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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bayukov O. A., Savitskii A. F.
Заглавие : Application of the superexchange model to the evaluation method of exchange and 3d-electron transfer parameters in magnetodielectrics
Место публикации : Phys. Status Solidi B. - 1989. - Vol. 152, Is. 2. - P.K51-K53. - ISSN 0370-1972, DOI 10.1002/pssb.2221520236
Примечания : Cited References: 6
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sofronova S. N., Moshkina E. M., Nazarenko I. I., Seryotkin Yu. V., Nepijko S. A., Ksenofontov V., Medjanik K., Veligzhanin A. A., Bezmaternykh L. N.
Заглавие : Crystal growth, structure, magnetic properties and theoretical exchange interaction calculations of Cu2MnBO5
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2016. - Vol. 420. - P.309-316. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2016.07.019
Примечания : Cited References: 35. - X-ray diffraction experiment was carried out at the Centre on Molecular Design and Ecologically Safe Technologies at the Novosibirsk State University. The reported study was funded by Russian Foundation for Basic Research (RFBR) and Government of Krasnoyarsk Territory according to the research project No. 16-42-243028.
Предметные рубрики: SPIN-GLASS BEHAVIOR
SINGLE-CRYSTALS
SUPEREXCHANGE INTERACTIONS
LUDWIGITE
DIELECTRICS
CO3B2O6NI3B2O6
WARWICKITES
FE3O2BO3
IFEFFIT
NI3B2O6
Ключевые слова (''Своб.индексиров.''): oxyborates--ludwigites--xmcd--exafs--magnetism
Аннотация: Single crystals of ludwigite Cu2MnBO5 were synthesized by flux growth technique. The detailed structural and magnetic characterizations of the synthesized samples have been carried out. The cations composition of the studied crystal was determined using X-ray diffraction and EXAFS technique, the resulting composition differ from the content of the initial Mn2O3–CuO components of the flux. Magnetic susceptibility measurements and the calculations of the exchange integrals in frameworks of indirect coupling model revealed that monoclinic distortions strongly affect exchange interactions and appearance of magnetic ordering phase at the temperature T=93 K. The hypothesis of the existence of several magnetic subsystems was supposed. © 2016 Elsevier B.V.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Kazak N. V., Nazarenko I. I., Sofronova S. N., Rostovtsev N. D., Bartolome J., Arauzo A., Ovchinnikov S. G.
Заглавие : Effect of magnetic frustrations on magnetism of the Fe3BO5 and Co3BO5 ludwigites
Место публикации : J. Magn. Magn. Mater. - 2019. - Vol. 474. - P.493-500. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2018.10.126
Примечания : Cited References: 33. - The Russian Foundation for Basic Research, Russia (project no. 17-02-00826-a ). S.G.O. thanks the Russian Academy of Science , Russia (project no. 0356-2017-0030 ) for financial support. J.B. and A.A. acknowledge the financial support of the Spanish MINECO-MAT2017-83468R project, Aragonese E-12 17R RASMIA (co-funded by Fondo Social Europeo), and the European Union (FEDER (ES)).
Ключевые слова (''Своб.индексиров.''): antiferromagnetics--superexchange interactions--frustrations
Аннотация: The magnetic structures of Fe3BO5 and Co3BO5 ludwigites have been studied experimentally by magnetic measurements and theoretically by the combination of the group theoretical analysis and semi empiric calculations of the superexchange interactions. The different collinear spin configurations in the triads 3-1-3 and 4-2-4 including ferromagnetic, antiferromagnetic and dimer have been considered. For Fe3BO5 the antiferromagnetic state with zero magnetic moment per unit cell, showing the lowest energy, results to be the most probable magnetic ground state. The unusual magnetic structure comprising two virtually independent orthogonal subsystems is formed to avoid heavy frustrations of superexchange interactions between the 3-1-3 and 4-2-4 spin ladders. In Co3BO5 the magnetic frustrations present for the Co3+ high-spin state are quenched for a Co3+ low spin state resulting in the ferrimagnetic long-range order. The obtained results are discussed in comparison with experimental magnetic data.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Troyanchuk I. O., Bushinsky M. V., Sikolenko V., Efimov V., Volkov N. V., Tobbens D. M., Ritter C., Raveau B.
Заглавие : Ferromagnetism in single-valent manganites
Место публикации : J. Alloys Compd.: Elsevier Science, 2015. - Vol. 619. - P.719-725. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2014.08.236. - ISSN 1873-4669
Примечания : Cited References: 46. - The authors would like to thank J.B. Goodenough for the fruitful discussion. This work has been supported by Belarusian Republican Foundation for Fundamental Research (Grant F14R-040).
Предметные рубрики: PHASE-SEPARATION
DOPED MANGANITES
DOUBLE EXCHANGE
DIFFRACTION
OXIDES
NMR
Ключевые слова (''Своб.индексиров.''): magnetically ordered materials--solid state reactions--exchange and superexchange--magnetic measurements--neutron diffraction
Аннотация: Structural and magnetization measurements have been performed on the La0.7Sr0.3Mn0.85 Nb 0.15 - x 5 + Mg x 2 + O3 stoichiometric compounds. With rise of the Mg2+ content the formal oxidation state manganese increases from +3 ( x = 0 ) up to +3.55 ( x = 0.15 ) . The compositions with 0 ⩽ x ≤ 0.08 undergo a structural transition from rhombohedral to orthorhombic symmetry below room temperature whereas x = 0.1 and x = 0.15 compounds are rhombohedral down to 2 K. The structural parameters evidence that the orthorhombic phase is not long-range orbitally ordered and that the structural transition is associated with a steric effect. The Mg-free compound is ferromagnetic with the Curie point of around 150 K and a magnetic moment of 3.1 μ B /Mn. The substitution of Nb5+ with Mg2+ leads to a gradual weakening of the ferromagnetic component while in the x = 0.15 compound A-type antiferromagnetic short-range order is stabilized in spite of macroscopic R 3 ¯ c symmetry. All the compositions show insulating behavior. It is suggested that ferromagnetism is originated from superexchange interactions via oxygen. Covalence enhances the positive part of the superexchange interactions whereas structural disorder induced by Nb5+ and Mg2+ ions leads to suppression of ferromagnetism.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I., Ovchinnikov S. G.
Заглавие : Cation spin and superexchange interaction in oxide materials below and above spin crossover under high pressure [Electronic resource]
Место публикации : ArXiv. - 2019. - Ст.1911.06482
Вид и объем ресурса: Electronic text data
Примечания : Cited References: 63. - We acknowledge the support of the Russian Science Foundation through Grant 18-12-00022.
Предметные рубрики: Materials Science
Strongly Correlated Electrons
Аннотация: We derived simple rules for the sign of superexchange interaction based on the multielectron calculations of the superexchange interaction in the transition metal oxides that are valid both below and above spin crossover under high pressure. The superexchange interaction between two cations in dn configurations is given by a sum of individual contributions related to the electron-hole virtual excitations to the different states of the dn+1 and dn−1 configurations. Using these rules, we have analyzed the sign of the superexchange interaction of a number of oxides with magnetic cations in electron configurations from d2 till d8: the iron, cobalt, chromium, nickel, copper and manganese oxides with increasing pressure. The most interesting result concerns the magnetic state of cobalt and nickel oxides CoO, Ni2O3 and also La2CoO4, LaNiO3 isostructural to well-known high-TC and colossal magnetoresistance materials. These oxides have a spin 12 at the high pressure. Change of the interaction from antiferromagnetic below spin crossover to ferromagnetic above spin crossover is predicted for oxide materials with cations in d5(FeBO3) and d7(CoO) configurations, while for materials with the other dn configurations spin crossover under high pressure does not change the sign of the superexchange interaction.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I., Ovchinnikov S. G.
Заглавие : Cation spin and superexchange interaction in oxide materials below and above spin crossover under high pressure
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [18-12-00022]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 9. - Ст.094409. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.094409. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 65. - We acknowledge the support of the Russian Science Foundation through Grant No. 18-12-00022
Предметные рубрики: EXCHANGE INTERACTION
PHASE-TRANSITIONS
STATE
ELECTRON
IRON
Аннотация: We derived simple rules for the sign of 180° superexchange interaction based on the multielectron calculations of the superexchange interaction in the transition metal oxides that are valid both below and above spin crossover under high pressure. The superexchange interaction between two cations in dn configurations is given by a sum of partial contributions related to the electron-hole virtual excitations to the different states of the dn+1 and dn−1 configurations. Using these rules, we have analyzed the sign of the 180° superexchange interaction of a number of oxides with magnetic cations in electron configurations from d2 until d8: the iron, cobalt, chromium, nickel, copper, and manganese oxides with increasing pressure. The most interesting result concerns the magnetic state of cobalt and nickel oxides CoO, Ni2O3 and also La2CoO4, LaNiO3 isostructural to well-known high-TC and colossal magnetoresistance materials. These oxides have a spin 12 at the high pressure. Change of the interaction from antiferromagnetic below spin crossover to ferromagnetic above spin crossover is predicted for oxide materials with cations in d5(FeBO3) and d7(CoO) configurations, while for materials with the other dn configurations spin crossover under high pressure does not change the sign of the 180∘ superexchange interaction.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I., Ovchinnikov S. G.
Заглавие : Contribution from optically excited many-electron states to the superexchange interaction in Mott-Hubbard insulators
Место публикации : Phys. Rev. B: American Physical Society, 2017. - Vol. 95, Is. 14. - Ст.144424. - ISSN 10980121 (ISSN), DOI 10.1103/PhysRevB.95.144424
Примечания : Cited References: 49. - This work was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory and Krasnoyarsk Region Science and Technology Support Fund to the research Project No. 17-42-240212. We are also grateful to the RFBR Grants No. 16-02-00273, No. 16-02-00098, and No. NSh-7559.2016.2.
Аннотация: We investigated the effects of excited many-electron states in the optical control of the magnetic state in undoped Mott-Hubbard insulator. To derive the spin Hamiltonian in material under optical pumping one has used a many-electron approach based on the X-operator representation. Extending the projection operators approach on arbitrary energy spectra of the Mott-Hubbard insulator, we obtained the Hamiltonian of superexchange interaction in analytical form. The Hamiltonian includes the spin-exciton variables which are usually missing in discussion on the magnetic response to optical pumping. The superexchange is also not additive over contributions from the ground and optical excited states, and nonzero contributions to the Dzyaloshinskii-Moriya interaction are induced in insulators with different spins at the ground and excited cell states. As a test, a microscopic background for the optical induced superexchange was analyzed in La2CuO4 (further La214) and FeBO3 with spins 1/2 and 5/2, respectively. © 2017 American Physical Society.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I.
Заглавие : Magnetic interaction in doped 2D perovskite cuprates with nanoscale inhomogeneity: Lattice nonlocal effects vs. superexchange
Место публикации : Condens. Matter. - 2022. - Vol. 7, Is. 4. - Ст.57. - ISSN 24103896, DOI 10.3390/condmat7040057
Примечания : Cited References: 78. - This work was supported by the Russian Science Foundation, research grant RSF No.22-22-00298
Аннотация: We have studied the superexchange interaction Jij in doped 2D cuprates. The AFM interaction strongly depends on the state of the lattice of a CuO2 layer surrounded by two LaO rock salt layers. In a static U and D stripe nanostructure, the homogeneous AFM interaction is impossible due to the U/D/U… periodic stripe sequence and TN=0. In a dynamic stripe nanostructure, the ideal CuO2 layer with nonlocal effects and the homogeneous AFM interaction are restored. However, the interaction Jij decreases by the exponential factor due to partial dynamic quenching. The meaning of the transition from the dynamic to the static cases lies in the spontaneous θ-symmetry breaking with respect to the rotation of all the tilted CuO6 octahedra by an orientation angle δθ=n⋅(45°) (where n=1÷4) in the U and D stripe nanostructure of the CuO2 layer. Moreover, the structural features help to study various experimental data on the charge inhomogeneity, Fermi level pinning in the p type cuprates only and time reversal symmetry breaking from a unified point of view.
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9.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I.
Заглавие : Magnetic interaction in doped 2D perovskites with nanoscale inhomogenety: lattice nonlocal effects vs superexchange
Коллективы : "Сильно коррелированные электронные системы и квантовые критические явления", конференция, Российская академия наук, Физический институт им. П.Н. Лебедева РАН
Место публикации : XIX Конференция "Сильно коррелированные электронные системы и квантовые критические явления": сборник тезисов/ чл. прогр. ком. С. Г. Овчинников и др. - Москва, 2022. - P.194-196. - ISBN 978-5-4344-0954-4
Примечания : Библиогр.: 1
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10.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gavrichkov V. A.
Заглавие : Superexchange in 2D perovskite HTSC with stripe nanostructure
Коллективы : "Functional materials", International conference, Крымский федеральный университет имени В.И. Вернадского
Место публикации : Ovchinnikov S. G. International conference "Functional materials": book of abstracts/ ed. V. N. Berzhansky ; org. com. S. G. Ovchinnikov [et al.]. - Simferopol, 2021. - P.223-2224
Примечания : Библиогр.: 3 назв. - The reported study was supported by the grant RFFI 19-02-00034 and the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, and Krasnoyarsk Regional Fund of Science according to the research project ”Studies of superexchange and electron-phonon interactions in correlated systems as a basis for searching for promising functional materials No. 20-42-240016.
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