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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Polukeev S. I., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Dependence of superexchange interaction in CrO2 on pressure
Коллективы : Российская академия наук, Уральское отделение РАН, Институт физики металлов им. М. Н. Михеева Уральского отделения РАН, Уральский федеральный университет им. первого Президента России Б.Н. Ельцина, Российский фонд фундаментальных исследований, Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : Euro-asian symposium "Trends in magnetism" (EASTMAG-2019): Book of abstracts/ чл. конс. ком.: S. G. Ovchinnikov, N. V. Volkov [et al.] ; чл. прогр. ком. D. M. Dzebisashvili [et al.]. - 2019. - Vol. 2. - Ст.H.P19. - P.103. - ISBN 978-5-9500855-7-4 (Шифр В33/E12-125657784)
Примечания : Cited References: 3. - Support by RSF grant 18-12-00022 is acknowledged
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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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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Polukeev S. I., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Dependence of superexchange interaction in CrO2 on pressure
Коллективы : Институт физики металлов им. М. Н. Михеева Уральского отделения РАН, Институт электрофизики УрО РАН, Международная зимняя школа физиков-теоретиков "Коуровка", "Коуровка", международная зимняя школа физиков-теоретиков
Место публикации : Международная зимняя школа физиков-теоретиков "Коуровка-XXXVIII": тезисы докладов : Верхняя Сысерть, 23 - 29 февр. 2020 г. - Екатеринбург, 2020. - P.70. - ISBN 978-5-9500855-9-8
Примечания : Cited References: 3. - Support by RSF grant № 18-12-00022 is acknowledged
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I., Ovchinnikov S. G.
Заглавие : Superexchange interaction in magnetic insulators with spin crossover
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 127, Is. 4. - P.713-720. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776118100023
Примечания : Cited References: 34. - This work was supported by the Russian Science Foundation (project no. 18-12-00022).
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--ground state--high pressure engineering--ions--iron compounds--magnetic materials
Аннотация: We present the derivation of a microscopic superexchange Hamiltonian for undoped magnetic insulators with an arbitrary spin. It is established that the sign of the (ferromagnetic or antiferromagnetic) superexchange between magnetic ions in the dn configuration depends on the spin nature of virtual multielectron states dn± 1, viz., low-spin or high-spin partners with S ± 1/2 relative to ground state of the dn configuration with spin S. A macroscopic substantiation is given for the Goodenough–Kanamori rules and simple mean-field estimates connecting the magnetic ordering temperature with the exchange constant. The conventional Anderson superexchange for magnetic materials with spin S = 1/2 and the P/T magnetic phase diagram for ferroborate FeBO3 with spin crossover S = (5/2 ↔ 1/2) at the Fe3+ ion under a high pressure are also reproduced as a test.
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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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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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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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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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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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10.

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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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Martynov S. N.
Заглавие : Ground State of a Two-Sublattice Anisotropic Ferromagnet in a Magnetic Field
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Krasnoyarsk Territorial Foundation [20-42-240006]
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 8. - P.1253-1261. - ISSN 1063-7834, DOI 10.1134/S1063783421080199. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 38. - This study was supported by the Russian Foundation for Basic Research and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project no. 20-42-240006 "Synthesis and Study of Pb2+-and Bi3+Containing Oxide Single Crystals with Partial Substitution in One of the Subsystems: Magnetic Structures and Magnetodielectric Effect"
Предметные рубрики: ANTIFERROMAGNETIC-RESONANCE
SUPEREXCHANGE INTERACTION
WEAK FERROMAGNETISM
Аннотация: The ground state of a classical two-sublattice ferromagnet with the noncollinear single-ion anisotropy axes of the sublattices and the antisymmetric and anisotropic symmetric exchanges between them has been investigated in a magnetic field applied along the hard magnetization directions in the crystal. The threshold relations for the parameters of the anisotropic interactions have been obtained, which determine the choice of the ground state among the three possible magnetic phases. Depending on the ground state type and the field direction, the transition between the phases is a first- or second-order phase transition. The antisymmetric exchange value above which the reorientation between the noncollinear phases ends with a second-order transition depends on the angle between the local easy axes and the single-ion anisotropy value. Field dependences of the magnetization and susceptibility for different ground states have been calculated. A comparison with the results of the magnetic measurements in the highly anisotropic PbMnBO4 ferromagnet has been made.
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12.

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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13.

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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14.

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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15.

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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16.

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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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : KRUSTALEV B. P., BALAEV A. D., SOSNIN V. M.
Заглавие : EXCHANGE INTERACTIONS IN SUPERPARAMAGNETIC NANOCLUSTER FILMS FE-SIO
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 1995. - Vol. 95, Is. 5. - P271-275. - ISSN 0038-1098, DOI 10.1016/0038-1098(95)00264-2
Примечания : Cited References: 9
Ключевые слова (''Своб.индексиров.''): nanostructures--thin films--exchange and superexchange
Аннотация: The magnetic properties of superparamagnetic films Fe-SiO have been investigated. It has been shown that a proper consideration of intra- and intercluster interactions describes well the magnetic behavior of the films. Their main parameters have been determined. On the basis of a proposed cluster model, the decrease of the effective magnetic moment per one iron atom is explained.
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18.

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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19.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Knyazev Yu.V., Bayukov O. A., Ivanova N. B., Kazak N. V., Bezmaternykh L. N., Platunov M. S., Arauzo A., Bartolomé J., Ovchinnikov S. G.
Заглавие : Magnetic structure of CoFeBO4 warwickite in terms of superexchange
Коллективы : Moscow International Symposium on Magnetism, Московский государственный университет им. М.В. Ломоносова
Место публикации : Moscow Int. Symp. on Magnet. (MISM-2014): Book of abstracts. - 2014. - Ст.1PO-I1-12. - P.447. - ISBN 978-5-91978-025-0
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20.

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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