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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Ivanova N. B., Rudenko V. V., Ovchinnikov S. G., Vasil'Ev A. D., Knyazev Yu. V.
Заглавие : Conductivity study of Co3O2BO3 and Co 3-xFexO2BO3 oxyborates
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Solid State Phenomena. - 2009. - Vol. 152-153. - С. 104-107. - ISSN 10120394 (ISSN); 390845168X (ISBN); 9783908451686 (ISBN), DOI 10.4028/www.scientific.net/SSP.152-153.104
Ключевые слова (''Своб.индексиров.''): doped cobaltite--electrical conductivity--ludwigite--variable-range hopping--crystal structure--electric conductivity--magnetic materials--single crystals--crystal structure--electric conductivity--magnetic materials--magnetism--single crystals--electrical conductivity--electrical resistivity--experimental data--mott variable-range hopping--oxyborates--temperature regions--variable-range hopping--doped cobaltite--ludwigite--variable range hopping--cobalt--cobalt
Аннотация: Single crystals of cobalt oxyborates Co3O2BO 3 and Co3-xFexO2BO3 were synthesized. The crystal structure and electric properties were investigated. The difference in the electrical resistivity behaviors was found. For parent Co3O2BO3 nor simple activation law, nor Mott variable range hopping (VRH) are acquirable to describe the experimental data in wide temperature region. In contrast for Co3-xFex O 2BO3 Mott's variable-range hopping conductivity clearly dominates.
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2.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Kazak N. V., Bartolome J., Rudenko V. V., Vasil'ev A. D., Bayukov O. A., Knyazev Yu.V., Platunov M. S.
Заглавие : Distribution of Fe ions ludwigite structure of Co3-xFexO2BO3
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : V Euro-Asian simposium "Trend in MAGnetism": Nanomagnetism: abstracts. - Ekaterinburg, 2010. - P.378
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Kazak N. V., Knyazev Yu.V., Velikanov D. A., Bezmaternykh L. N., Ovchinnikov S. G., Vasiliev A. D., Platunov M. S., Bartolomé J., Patrin G. S.
Заглавие : Crystal structure and magnetic anisotropy of ludwigite Co2FeO2BO3
Место публикации : J. Experim. Theor. Phys. - 2011. - Vol. 113, Is. 6. - P.1015-1024. - DOI 10.1134/S1063776111140172
Примечания : Cited References: 14. - This work was supported by the Russian Founda tion for Basic Research (project no. 090200171a), the Russian Science Foundation (President project no. MK5632.2010.2), and the program of the Divi sion of Physical Sciences of the Russian Academy of Sciences “Strong Electronic Correlations.” REFE
Аннотация: Co3O2BO3 and Co2FeO2BO3 single crystals with a ludwigite structure are fabricated, and their crystal structure and magnetic properties are studied in detail. Substituted ludwigite Co2FeO2BO3 undergoes two-stage magnetic ordering at the temperatures characteristic of Fe3O2BO3 (T N1 ≈ 110 K, T N2 ≈ 70 K) rather than Co3O2BO3 (T N = 42 K). This effect is explained in terms of preferred occupation of nonequivalent crystallographic positions by iron, which was detected by X-ray diffraction. Both materials exhibit a pronounced uniaxial magnetic anisotropy. Crystallographic direction b is an easy magnetization axis. Upon iron substitution, the cobalt ludwigite acquires a very high magnetic hardness.
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4.

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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5.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Platunov M. S., Ovchinnikov S. G., Kazak N. V., Ivanova N. B., Rogalev A., Wilhelm F., Zabluda V. N.
Заглавие : XANES and XMCD study of ludwigite Co3BO5 and Co2FeBO5 single crystals
Коллективы : Magnetic Materials under Extreme Conditions. Workshop associated to the ESRF Users’ Meeting (2012 ; февр. ; 7-8; Grenoble, France)
Место публикации : MRS Fall Meeting and Exhibit . - 2012. - P.37
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu.V., Ivanova N. B., Kazak N. V., Platunov M. S., Bezmaternykh L. N., Velikanov D. A., Vasiliev A. D., Ovchinnikov S. G., Yurkin G. Yu.
Заглавие : Crystal structure and magnetic properties of Mn substituted ludwigite Co3O2BO3
Место публикации : J. Magn. Magn. Mater.: Elsevier Science BV, 2012. - Vol. 324, Is. 6. - P.923-927. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2011.07.044
Примечания : Cited References: 15. - The 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), the Physical Division of the Russian Academy of Science, the program "Strongly Correlated Electrons", Project 2.3.1.
Предметные рубрики: BOND VALENT SUMS
COORDINATION CHEMISTRY
OXIDATION -STATE
O BONDS
COMPLEXES
MANGANESE
COBALT
Ключевые слова (''Своб.индексиров.''): transition metal oxyborate--distinct crystallographic position--spin glass magnetic ordering
Аннотация: The needle shape single crystals Co3−x MnxO2BO3 with ludwigite structure have been prepared. According to the X-ray diffraction data the preferable character of distinct crystallographic positions occupation by Mn ions is established. Magnetization field and temperature dependencies are measured. Paramagnetic Curie temperature value Θ=−100 K points out the predominance of antiferromagnetic interactions. Spin-glass magnetic ordering takes the onset at TN=41 K. The crystallographic and magnetic properties of Co3O2BO3:Mn are compared with the same for the isostructural analogs Co3O2BO3 and CoO2BO3:Fe.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Platunov M. S., Knyazev Yu.V., Kazak N. V., Bezmaternykh L. N., Vasiliev A. D., Ovchinnikov S. G., Nizhankovskii V. I.
Заглавие : Effect of the diamagnetic dilution on the magnetic ordering and electrical conductivity in the Co3O2BO3 : Ga ludwigite
Место публикации : Phys. Solid State. - 2012. - Vol. 54, Is. 11. - P.2212–2221. - ISSN 1063-7834, DOI 10.1134/S1063783412110133
Примечания : Cited References: 30. - This study was supported by the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-1044.2012.2) and the Russian Foundation for Basic Research (project nos. 12-02-00175-a and 12-02-00470-a).
Аннотация: Single crystals of cobalt ludwigite Co3O2BO3 with diamagnetic substitution of Ga3+ ions for a part of the cobalt ions have been grown by the flux method. A detailed investigation of the crystal structure and magnetic properties of the compound has been carried out. A preferred character of the occupation of non-equivalent crystallographic positions by gallium has been revealed. It has been found that the effective magnetic moment and the magnetic ordering temperature are decreased compared to those in the original crystal of the Co3O2BO3 ludwigite. It has been noted that the pronounced magnetic anisotropy observed in the crystal lographic ab plane of the original material of the Co3O2BO3 composition disappears in the presence of gallium.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Platunov M. S., Knyazev Yu. V., Kazak N. V., Bezmaternykh L. N., Eremin E. V., Vasiliev A. D.
Заглавие : Spin-glass magnetic ordering in CoMgGaO2BO3 ludwigite
Место публикации : Физ. низких температур: Физико-технический институт низких температур им. Б.И. Веркина НАН Украины, 2012. - Т. 38, Вып. 2. - С.214-217. - ISSN 0132-6414. - ISSN 1816-0328
Примечания : Библиогр.: 13 назв. - This work 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), the Physics Division of the Russian Academy of Sciences, the program "Strongly Correlated Electrons" (project 2.3.1).
Предметные рубрики: AC Magnetic susceptibility
DC magnetization
Field cooled
Flux methods
Frequency dependent
Magnetic system
Magnetic transitions
Needle shape
Parent compounds
Spin-glasses freezing
Temperature dependencies
Unit-cell volume
Zero-field-cooled
Cobalt
Cobalt compounds
Freezing
Glass
Magnetic susceptibility
Magnetism
Single crystals
X-ray diffraction
Spin glass
Ключевые слова (''Своб.индексиров.''): spin-glass freezing--transition metal ludwigites
Аннотация: The single crystal needle shape samples of diamagnetically diluted cobalt ludwigite CoMgGaO2BO3 have been grown by the flux method. The results of x-ray diffraction and both dc and ac magnetic measurements are presented. The unit cell volume undergoes a noticable growth under dilution from 328.31 Å3 for the parent compound Co3O2BO3 to 345.46 Å3 for CoMgGaO2BO3. The temperature of magnetic transition is considerably lower for the latter compound (25 K against 43 Kfor Co3O2BO3). The dc magnetization temperature dependencies undergo the splitting of field cooled and zero-field cooled regimes and the ac magnetic susceptibility temperature dependencies are frequency dependent pointing out a possible spin-glass freezing in the magnetic system.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Platunov M. S., Knyazev Yu. V., Kazak N. V., Bezmaternykh L. N., Eremin E. V., Vasiliev A. D.
Заглавие : Spin-glass magnetic ordering in CoMgGaO2BO3 ludwigite
Место публикации : Low Temp. Phys.: American Institute of Physics, 2012. - Vol. 38, No. 2. - P.172-174. - ISSN 1063-777X, DOI 10.1063/1.3679627
Примечания : Cited References: 13. - This work 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), the Physics Division of the Russian Academy of Sciences, the program "Strongly Correlated Electrons" (project 2.3.1).
Аннотация: The single crystal needle shape samples of diamagnetically diluted cobalt ludwigite CoMgGaO2BO3 have been grown by the flux method. The results of x-ray diffraction and both dc and ac magnetic measurements are presented. The unit cell volume undergoes a noticable growth under dilution from 328.31 Å3 for the parent compound Co3O2BO3 to 345.46 Å3 for CoMgGaO2BO3. The temperature of magnetic transition is considerably lower for the latter compound (25 K against 43 Kfor Co3O2BO3). The dc magnetization temperature dependencies undergo the splitting of field cooled and zero-field cooled regimes and the ac magnetic susceptibility temperature dependencies are frequency dependent pointing out a possible spin-glass freezing in the magnetic system.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Platunov M. S., Ivanova N. B., Knyazev Yu. V., Bezmaternykh L. N., Eremin E. V., Vasil'ev A. D., Bayukov O. A., Ovchinnikov S. G., Velikanov D. A., Zubavichus Y. V.
Заглавие : Crystal structure and magnetization of a Co3B2O6 single crystal
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2013. - Vol. 117, Is. 1. - P.94-107. - ISSN 1063-7761, DOI 10.1134/S1063776113060186
Примечания : Cited References: 43. - The synchrotron measurements were performed at the Kurchatov Center of Synchrotron Radiation and Nanotechnologies (state contract no. 16.552.11.7055).This work was supported by the Russian Foundation for Basic Research (project nos. 12-02-00175-a, 12-02-90410-Ukr_a, 12-02-31543mol_a, 13-02-00958-a), the President of the Russian Federation (grant no. NSh-1044.2012.2), the Siberian Branch of the Russian Academy of Sciences (project no. 38), the Ministry of Education and Science of the Russian Federation (project no. 8365), and an integration project of SO RAN-NAN of Belarus (project no. 29).
Предметные рубрики: ABSORPTION FINE-STRUCTURE
NICKEL ORTHOBORATE
RAY
GDFE3(BO3)(4)
LUDWIGITE
NI3(BO3)2
NI3B2O6
SPECTRA
Аннотация: The crystal structure and magnetic properties of Co3B2O6 single crystals are studied. Orthorhombic symmetry with space group Pnnm is detected at room temperature. The measurements of static magnetization and dynamic magnetic susceptibility reveal two magnetic anomalies at T (1) = 33 K and T (2) = 10 K and an easy-axis magnetic anisotropy. The effective magnetic moment indicates a high-spin state of the Co2+ ion. A spin-flop transition is found at low temperatures and H (sf) = 23 kOe. EXAFS spectra of the K-edge absorption of Co are recorded at various temperatures, the temperature-induced changes in the parameters of the local environment of cobalt are analyzed, and the effective Co-Co and Co-O distances are determined. The magnetic interactions in the crystal are analyzed in terms of an indirect coupling model.
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