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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : ZAMKOVA N. G., ZINENKO V. I.
Заглавие : THERMODYNAMICS OF THE 2-DIMENSIONAL SUPEREXCHANGE MODEL OF MITSUI
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1989. - Vol. 79, Is. 2. - P530-536. - ISSN 0040-5779, DOI 10.1007/BF01016535
Примечания : Cited References: 14
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2.

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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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Bayukov O. A., Ovchinnikov S. G., Vasiliev A. D., Rudenko V. V., Ivanova N. B., Knyazev Yu. V., Bartolom J., Arauzo A.
Заглавие : The superexchange interactions in mixed Co-Fe ludwigite
Место публикации : J. Magn. Magn. Mater. - 2011. - Vol. 323, Is. 5. - P.521-527. - MAR. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2010.09.057
Примечания : Cited Reference Count: 15. - Гранты: This study was supported by the Russian Foundation for Basic Research (Project no. 09-02-00171-a), the Federal Agency for Science and Innovation (Rosnauka) (Project no. MK-5632. 2010.2), Physical Division of the Russian Academy of Science, the program "Strongly Correlated Electrons", project 2.3.1.; The financial support of Spanish MINCYT, MAT08/1077 and Aragonese E-34 project are also acknowledged.Финансирующая организация: Russian Foundation for Basic Research [09-02-00171-a]; Federal Agency for Science and Innovation (Rosnauka) [MK-5632. 2010.2]; Physical Division of the Russian Academy of Science; "Strongly Correlated Electrons" [2.3.1]; Spanish MINCYT [MAT08/1077]; Aragonese E-34 project
Предметные рубрики: TRANSPORT-PROPERTIES
SPECTRA
Ключевые слова (''Своб.индексиров.''): ludwigite structure--magnetic susceptibility--magnetic frustration--mott conductivity--ludwigite structure--magnetic frustration--magnetic susceptibility--mott conductivity--ac susceptibility--cation distributions--crystal data--crystallographic sites--electrical resistivity--iron atoms--low temperatures--ludwigite structure--magnetic behavior--magnetic frustrations--magnetic system--magnetic transitions--mossbauer--mossbauer effects--mott conductivity--mott hopping--superexchange energy--superexchange interaction--temperature regions--trivalent iron--variable range--cobalt--electric conductivity--magnetic susceptibility--magnetism--mossbauer spectroscopy--x ray diffraction--crystal structure
Аннотация: The crystal structure, cation distribution and exchange interactions in the Co2.25Fe0.75O2BO3 ludwigite have been explored through X-ray diffraction, electrical resistivity, ac-susceptibility and Mossbauer effect measurements. The crystal data have shown that iron atoms occupy the most symmetric crystallographic sites Fe4 and Fe2. The complex magnetic behavior with two magnetic transitions near 70 and 115 K at low temperatures was found. The Mossbauer data have displayed the trivalent iron states only. The values of superexchange energies have been estimated for Co3O2BO3 and Co2.25Fe0.75O2BO3 yielding a significant role of frustrations in the ludwigite magnetic system. Variable range Mott hopping conductivity law was proved to be valid in the wide temperature region, pointing out a localized character of charge carriers rather than collective. (C) 2010 Elsevier B.V. All rights reserved.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sofronova S. N., Bezmaternykh L. N., Eremin E. V., Nazarenko I. I., Volkov N. V., Kartashev A. V., Moshkina E. M.
Заглавие : The superexchange interactions and magnetic ordering in low-dimentional ludwigite Ni5GeB2O10
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2016. - Vol. 401. - P.217-222. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2015.10.024
Примечания : Cited References: 23. - This study was supported by Russian Foundation for Basic Research (RFFI Siberia No. 15-42-04186). We thank S. Popkov, G. Yurkin for help on the magnetic measurements and M.S. Molokeev for help on the x-ray diffraction
Предметные рубрики: DIELECTRICS
EXCHANGE
CATION
Ключевые слова (''Своб.индексиров.''): ludwigites--magnetic order--heat capacity--exchange interactions--ferrimagnetic
Аннотация: The ludwigite Ni5Ge(BO5)2 belongs to a family of oxyborates which have low-dimensional subunits in the form of three-leg ladders unit structure. This material was studied by magnetic and thermodynamic measurements. Ni5Ge(BO5)2 does not show full long-range magnetic order, but one goes into a partial ordering or spin-glass state at 87 K. The superexchange interactions were calculated in the framework of a simple indirect coupling model. Different models of magnetic structure of Ni5Ge(BO5)2 and its unique magnetic behaviour was discussed. © 2015 Elsevier B.V.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sofronova S. N., Nazarenko I. I.
Заглавие : Super-Superexchange Influence on Magnetic Ordering in Ni3B2O6 Kotoite
Место публикации : Phys. Status Solidi B. - 2019. - Vol. 256, Is. 10. - Ст.1900060. - ISSN 03701972 (ISSN) , DOI 10.1002/pssb.201900060
Примечания : Cited References: 22. - The study was carried out with the financial support of the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory, the Krasnoyarsk Regional Science Foundation as part of a research project: “Low-dimensional and frustrated magnetism in nickel oxyborates and manganites with the substitution of manganese by Yang-Teller ions,” No. 18-42-240007.
Аннотация: Using ab initio software package WIEN2k, the calculations of electronic propertiesand of the energies of various magnetically ordered structures are carried out and possible mechanisms of magnetic ordering are analyzed in Ni3B2O6. The superexchange (Ni-O-Ni) and super-superexchange interactions (Ni-O-B-O-Ni) are calculated, a magnetic ordering model is proposed.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sofronova S. N., Chernyshev A.
Заглавие : Magnetic ordering and the role of superexchange Ni–O–B–O–Ni upon the formation of magnetic order in ludwigite Ni2MnBO5 from first-principal calculations
Место публикации : Comput. Condens. Matter. - 2024. - Vol. 40. - Ст.e00918. - ISSN 23522143 (eISSN), DOI 10.1016/j.cocom.2024.e00918
Примечания : Cited References: 28
Аннотация: The energies of various magnetically ordered structures for ludwigite Ni2MnBO5 have been calculated in the framework of the first-principles approach using the Wien2K program package, with the parameters of exchange interactions being determined. Two subsystems can be distinguished in the magnetic system, which are associated with the triads 4-2-4 and 3-1-3. The magnetic moments of the ions in both triads are antiferromagnetically oriented. The analysis of the exchange contribution to the energy shows that there occurs an increase of the magnetic cell relative to the crystallographic one due to antiferromagnetic ordering of the magnetic moments along the c axis in three-legged ladders formed by 4-2-4 triads. However, in three-legged ladders formed by 3-1-3 triads, the magnetic moments of the ions are ordered along the c-axis ferromagnetically. The predicted type of magnetic ordering in Ni2MnBO5 is similar to magnetic ordering in Fe3BO5. Non-collinear ordering of the magnetic moments of the subsystems at different temperatures is also likely to be observed in Ni2MnBO5, as is the case in Fe3BO5. Superexchange (indirect) interactions (No-O-B-O-Ni) influence the orientation of the magnetic moments of two 3-1-3 (4-2-4) triads within the unit cell. It is these interactions that may be responsible for the formation of long-range magnetic order in Co3BO5 and ferrimagnetic-antiferromagnetic spin-reorientation transition in Fe3BO5.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Troyanchuk I. O., Bushinsky M. V., Volkov N. V., Sikolenko V., Efimova E. A., Ritter C.
Заглавие : Role of superexchange interactions in the ferromagnetism of manganites
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 120, Is. 1. - P.97-102. - ISSN 1063, DOI 10.1134/S1063776115010173. - ISSN 10906509(eISSN)
Примечания : Cited References:25. - This work was supported by the Belarussian Foundation for Basic Research, project no. F12SO-026.
Предметные рубрики: PHASE
NMR
Аннотация: Compound La0.7Sr0.3Mn0.85Nb0.15O3, in which manganese ions are in an oxidation state close to 3+, are studied by neutron diffraction and magnetic measurements. This compound is shown to be a ferromagnet with T C = 145 K and a magnetic moment of 3.1 μB/Mn at T = 10 K. No signs of cooperative orbital ordering are detected. When Mg2+ ions substitute for some Nb5+ ions, Mn4+ ions appear but ferromagnetism is not enhanced. An increase in the structural distortions leads to a decrease in the ferromagnetic component. The ferromagnetic state is assumed to be caused by substantial hybridization of the e g orbitals of manganese and oxygen, which increases the positive part of the superexchange interactions.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Pchelkina Z. V., Nekrasov I. A., Ovchinnikov S. G.
Заглавие : Pressure effect on the energy structure and superexchange interaction in undoped orthorhombic La2CuO4
Место публикации : Int. J. Mod. Phys. B: World Scientific Publishing, 2016. - Vol. 30, Is. 25. - ISSN 02179792 (ISSN), DOI 10.1142/S0217979216501800
Ключевые слова (''Своб.индексиров.''): antiferromagnetic la214--pressure--superexchange interaction
Аннотация: We studied the pressure dependences of the electronic structure and superexchange interaction J(P)=JA−JB (where JA and JB are antiferromagnetic (AFM) and ferromagnetic (FM) contributions) in antiferromagnetic La214 under hydrostatic, uniaxial (along c-axial) 3% compressions and 1% in-plane compressions by the local density approximation with generalized tight-binding method (LDA + GTB cell approach). The changes in J(P) correlated with the experimentally known TC(P) dependence are in accordance with the relation dTC/dP=(∂TC/∂J)(∂J/∂P), where ∂TC/∂J∼0.1. The in-plane pressure more effectively stabilizes the ground singlet two-hole state A1 than the simple hydrostatic pressure, its effect on J and TC is the largest. Within the same cell approach together with the superexchange interaction J(P), the valence band structure was calculated. Its changes with pressure clearly reproduce the k-distribution of the singlet and triplet quasi-particles over the Brillouin zone (BZ).
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9.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Polukeev S. I., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : In-gap excitation effect on a superexchange in La2CuO4 by creating a nonequilibrium photoexcited centers
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : VI Euro-Asian Symposium "Trends in MAGnetism" (EASTMAG-2016): abstracts/ ed.: O. A. Maksimova, R. D. Ivantsov. - Krasnoyarsk: KIP RAS SB, 2016. - Ст.P1.30. - P.90-91. - ISBN 978-5-904603-06-9 (Шифр -478014040)
Примечания : References: 10. - This work was supported by RFBR Grant 16-02-00273
Ключевые слова (''Своб.индексиров.''): superexchange--mott-hubbard materials--light pumping--la214
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Polukeev S. I., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Exchange interaction in LaCoO3 between cobalt ions Co3+ in different spin states
Место публикации : Phys. Solid State. - 2022. - Vol. 64, Is. 12. - P.1887-1890. - ISSN 10637834 (ISSN), DOI 10.21883/PSS.2022.12.54381.426. - ISSN 10906460 (eISSN)
Примечания : Cited References: 38. - The work was carried out with the financial support of the Russian Foundation for Basic Research (project No. 20-42-240016)
Аннотация: The values and signs of the contributions to the superexchange interaction of Co3+ ions in LaCoO3 in different spin states, namely, the superexchange of a pair of ions in the intermediate (IS) state and the superexchange of a pair of ions, one of which is in the intermediate state and the other in the high-spin (HS) state, are studied. For this purpose, virtual electron-hole pairs produced in the course of superexchange (the so-called exchange loops) have been studied within the framework of a multiband generalization of the Hubbard model. It is shown that the cobalt ions in the intermediate state are ordered ferromagnetically, while a pair of ions in different HS and IS states makes an AFM contribution to the superexchange.
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