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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Балаев, Дмитрий Александрович, Дубровский, Андрей Александрович, Шайхутдинов, Кирилл Александрович, Попков, Сергей Иванович, Петров, Михаил Иванович
Заглавие : Особенности временной эволюции магнитосопротивления гранулярных ВТСП в постоянном магнитном поле
Коллективы : "Фундаментальные проблемы высокотемпературной сверхпроводимости", международная конференция, Физический институт им. П.Н. Лебедева РАН
Место публикации : Третья международная конференция "Фундаментальные проблемы высокотемпературной сверхпроводимости" ФПС'08: 13-17 окт., Звенигород, 2008 : сборник трудов. - С. 117-118
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Петров, Михаил Иванович, Гохфельд Ю.С., Балаев, Дмитрий Александрович, Попков, Сергей Иванович, Дубровский, Андрей Александрович, Гохфельд, Денис Михайлович, Шайхутдинов, Кирилл Александрович
Заглавие : Локальные искажения электронной плотности как центры пиннинга в Y1−xRExBa2Cu3O7−δ
Коллективы : "Фундаментальные проблемы высокотемпературной сверхпроводимости", международная конференция
Место публикации : Третья Междунар. конф. "Фундам. пробл. высокотемпер. сверхпроводимости" ФПС'08: 13-17 окт., Звенигород, 2008 : сборник трудов. - С. 156-157
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Petrov M. I., Gokhfeld Yu. S., Balaev D. A., Popkov S. I., Dubrovskiy A. A., Gokhfeld D. M., Shaykhutdinov K. A.
Заглавие : Pinning enhancement by heterovalent substitution in Y1−xRExBa2Cu3O7−δ
Место публикации : 25th International Conference on Low Temperature Physics (LT25). – Amsterdam, Netherlands. - August 6-13. – 2008. – PB-Tu130, p.304
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Platunov M. S., Fedorova N. A., Pyastolova Yu. V., Laptash N. M., Knyazev Yu. V., Tomilin F. N., Dubrovskiy A. A.
Заглавие : Unraveling dynamic Jahn-Teller effect and magnetism in FeTiF6×6H2O single crystal
Колич.характеристики :9 с
Место публикации : J. Alloys Compd. - 2024. - Vol. 999. - Ст.175104. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2024.175104. - ISSN 18734669 (eISSN)
Примечания : Cited References: 51. - The authors thank the Joint Supercomputer Center (JSCC) of the Russian Academy of Sciences. The authors would like to express their sincere gratitude to the ID12 beamline staff their exceptional dedication and professionalism in performing the synchrotron experiment during the challenging circumstances of the COVID-pandemic. We are particularly grateful to the postdocs, scientists, and technicians who took part in the experiment, ensuring its successful completion. We also gratefully acknowledge the provision of beamtime (Proposal HC-4375) by the European Synchrotron Radiation Facility (ESRF). The access to this world-class facility was instrumental in obtaining the high-quality data that formed the basis of our research. We are deeply appreciative of the contributions of all involved, and we extend our heartfelt thanks to each and every one of them
Аннотация: Hydrated iron fluoridotitanate (FeTiF6 × 6 H2O) single crystals are fascinating magnetic materials with unique properties. To understand the underlying mechanisms, this study combines X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) techniques, complemented by density functional theory (DFT) calculations. Polarization-dependent X-ray absorption spectroscopy, encompassing XANES and XMCD, is a powerful technique for probing the local structures and magnetic properties of materials. It is element-selective, bulk-sensitive, and compatible with a wide range of experimental conditions. In this study, we used XANES and XMCD spectroscopies to investigate the local structures and magnetic properties of Fe and Ti in FeTiF6 × 6 H2O single crystals. XANES analysis revealed distinct local environments around Fe and Ti, providing insights into their coordination environments. Element-selective magnetization measurement at the Fe K-edge demonstrated that iron sites in the oxidation state Fe2+ have an unambiguous paramagnetic contribution to the magnetization along the b-axis. Notably, the absence of an XMCD signal at the Ti K-edge confirmed the absence of a magnetic moment in Ti atoms within the crystal. DFT calculations corroborate the experimental findings and provide insights into the electronic structure and magnetic interactions. The combined results provide a comprehensive understanding of the dynamic Jahn-Teller effect in FeTiF6 × 6 H2O single crystals, highlighting the significance of polarization-dependent X-ray absorption spectroscopy in unraveling the intricate magnetic behavior of such materials. This study contributes to the fundamental understanding of magnetism in these materials and paves the way for the development of novel magnetic materials with tailored properties.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkova E. A., Platunov M. S., Antipin A. M., Alpanova R. R., Dubrovskiy A. A., Pyastolova Yu. V., Podobraznyh A. D., Kosorukov V. L., Koporulina E. V., Maltsev V. V.
Заглавие : Synthesis, structure and magnetic properties of monoclinic lanthanum-chromium borate LaCr3(BO3)4
Колич.характеристики :9 с
Место публикации : J. Alloys Compd. - 2024. - Vol. 994. - Ст.174683. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2024.174683. - ISSN 1873-4669
Примечания : Cited References: 38. - Single crystal X-ray analysis was carried out within the State assignment NRC "Kurchatov institute" (research contribution of A.M.A.). The research contribution of M.S.P. was partially supported by the Ministry of Science and Higher Education of the Russian Federation within the governmental assignment for Synchrotron radiation facility "SKIF", Boreskov Institute of Catalysis (project FWUR-2024–0040)
Аннотация: Single crystals of LaCr3(BO3)4 were synthesized through spontaneous nucleation from a K2Mo3O10 flux melt. The crystal structure was determined using single-crystal X-ray diffraction (XRD) at temperatures of 293 K and 85 K. LaCr-borate crystallizes in the monoclinic C2/c space group with unit cell parameters a = 7.47980(5) Å, b = 9.55180(7) Å, c = 11.48330(8) Å, β= 104.0060(6)°, V = 796.04(1) Å3 (for C1, T = 293 K), and a = 7.47380(5) Å, b = 9.55520(7) Å, c = 11.47100(8) Å, β = 103.9330(6)°, V = 795.08(1) Å3 (for C2, T = 85 K), each with Z = 4. The temperature dependence of the unit cell parameters, including the monoclinic angle (β) and the unit cell volume (V), was investigated over the range of 85–293 K. No structural phase transitions were observed in the low-temperature region down to 85 K. Differential scanning calorimetry (DSC) measurements revealed no high-temperature phase transitions between 50 and 1350°C. Infrared (IR) spectroscopy confirmed the monoclinic structure of LaCr3(BO3)4 crystals, revealing characteristic absorption bands, including the lowest frequency mode associated with the translational vibrations of the La3+ ion.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Platunov M. S., Ikkert O. P., Semenov S. V., Bayukov O. A., Nikolenko A. D., Nazmov V. P., Volochaev M. N., Dubrovskiy A. A., Molokeev M. S., Smorodina E. D., Balaev D. A., Karnachuk O. V.
Заглавие : Microbially mediated synthesis of vivianite by Desulfosporosinus on the way to phosphorus recovery
Колич.характеристики :15 с
Место публикации : Environ. Sci.: Adv. - 2024. - Vol. 3, Is. 6. - P.897-911. - ISSN 27547000 (eISSN), DOI 10.1039/D4VA00040D
Примечания : Cited References: 120. - This study was supported by the Russian Science Foundation, project no. 22-24-00601 (https://rscf.ru/project/22-24-00601/). The electron microscopy and Mössbauer studies were carried out on the equipment of the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences. The research contribution of M. S. P. was partially supported by the Ministry of Science and Higher Education of the Russian Federation within the governmental assignment for Synchrotron radiation facility “SKIF”, Boreskov Institute of Catalysis (project FWUR-2024-0040)
Аннотация: We explored the role of biomineralization in industrial waste sludge formation, using the laboratory cultivation of Desulfovibrio sp. OL sulfate reducing species isolated from the Komsomolsky waste sludge (Russia). The most frequently reported sulfate-reducing bacteria (SRB) biomineralization products are various iron sulfides. Here we present first studies of the products of Desulfosporosinus metallidurans, acidophilic SRB from acid mine drainage. We analyzed the biomineralized sample using X-ray diffraction, electron microscopy, X-ray absorption and Mossbauer spectroscopies, and magnetization measurements via First-Order Reversal Curve (FORC) diagram analysis. Our findings show that the biomineralization occurring under pure culture conditions leads to the formation of greigite (Fe3S4) nanorods, along with larger microbially mediated crystals of vivianite (Fe3(PO4)2·8H2O) and siderite (FeCO3). Energy dispersive X-ray spectroscopy revealed that the crystal sizes of vivianite and siderite were comparatively larger than those of the nanorod-shaped greigite. Transmission electron microscopy and Mossbauer spectroscopy detected ultrafine ferrihydrite (Fe2O3·nH2O) superparamagnetic nanoparticles with an average size of 2.5 nm. FORC analysis showed significant magnetic interactions among these nanoparticles, suggesting their potential for magnetic separation applications. The current study demonstrates that ferrihydrite nanoparticles have a strong magnetic affinity for other crystal phases produced by Desulfosporosinus metallidurans. Therefore, we believe that the investigated bacterial species can be exploited in advanced magnetic separation techniques. This offers a cost-effective and environmentally friendly method for purifying sediments in industrial waste sludge.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Dubrovskiy A. A., Knyazev Yu. V., Velikanov D. A., Vorotynov A. M., Laptash N. M., Gerasimova Yu. V.
Заглавие : Giant anisotropy of magnetic properties of hydrated iron fluoridotitanate molecular single crystal
Коллективы : International Baltic Conference on Magnetism, Балтийский федеральный университет им. И. Канта
Место публикации : V International Baltic Conference on Magnetism. IBCM: Book of abstracts. - 2023. - P.57
Примечания : Cited References: 4. - РНФ № 23-22-10037 ; Красноярский регион. фонд науки
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gerasimova Yu. V., Aleksandrovsky A. S., Laptash N. M., Krylov A. S., Gerasimov M. A., Dubrovskiy A. A.
Заглавие : Raman scattering, absorption and luminescence spectroscopy of CoSiF6·6H2O crystal and CoSiF6·6H2O:Mn4+ red-emitting phosphor
Колич.характеристики :6 с
Место публикации : Opt. Mater. - 2023. - Vol. 144. - Ст.114343. - ISSN 09253467 (ISSN), DOI 10.1016/j.optmat.2023.114343. - ISSN 18731252 (eISSN)
Примечания : Cited References: 30. - The reported study was funded by Russian Science Foundation , Government of Krasnoyarsk Territory and Krasnoyarsk Regional Foundation of Science according to the research project ‘‘Synthesis, spectral and magnetic properties of ABF6·6H2O systems, new materials for photonics.” No. 23-22-10037 . https://rscf.ru/en/project/23-22-10037/ . Usage of equipment of Krasnoyarsk Regional Center of Research Equipment of Federal Research Center “Krasnoyarsk Science Center SB RAS is acknowledged. We thank A. Yu. Mamaev for recording the luminesce spectra of CoSiF6·6H2O:Mn 4+
Аннотация: CoSiF6·6H2O and CoSiF6·6H2O:Mn4+ crystals were investigated by means of Raman, optical absorption, and luminescence spectroscopy. Absorption spectra of CoSiF6·6H2O are analyzed by Tanabe-Sugano technique and are proved to be well-describable at crystal field strength Dq = 1000 cm−1, and Racah parameters B = 896 cm−1, C = 4408 cm−1, Dq/B = 1.116. Raman spectroscopy reveals a phase transition associated with the ordering of both the CoO6 and SiF6 octahedra, which occurs through the ordering of the H2O subsystem. Luminescence spectrum of Mn4+ ions in CoSiF6·6H2O lattice consists of six components corresponding to Stokes and anti-Stokes emission from 2E state of Mn4+ ion at vibrational frequencies of MnF6 octahedron ν6 = 230 cm−1, ν4 = 335 cm−1, and ν3 = 645 cm−1. Quantum efficiency of red emission maximizes at excitation wavelength 357 nm and equals to 5%. Decrease of quantum efficiency in comparison to other related materials is explained by absorption of Co2+ ions and non-radiative relaxation in the Co2+ subsystem.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Omelyanchik A., Kamzin A. S., Valiullin A. A., Semenov V. G., Vereshchagin S. N., Volochaev M. N., Dubrovskiy A. A., Sviridova T., Kozenkov I., Dolan E., Peddis D., Sokolov A. Е., Rodionova V.
Заглавие : Iron oxide nanoparticles synthesized by a glycine-modified coprecipitation method: Structure and magnetic properties
Место публикации : Colloids Surf. A Physicochem. Eng. Asp. - 2022. - Vol. 647. - Ст.129090. - ISSN 09277757 (ISSN), DOI 10.1016/j.colsurfa.2022.129090
Примечания : Cited References: 80. - This work was supported by the Russian Science Foundation grant No. 21-72-20158 . The study of the structure was carried out on the equipment of the Center Collective Use " Materials Science and Metallurgy " which was purchased with the financial support of the Russian Federation represented by the Ministry of Education and Science (No. 075-15-2021-696)
Аннотация: Iron oxide magnetic nanoparticles (MNPs) are of interest in biomedicine and research owing to their moderate cytotoxicity and advanced properties, such as extensive surface-to-volume ratio and possibilities for tailoring their functionality through surface chemistry. To date, various approaches have been used for the synthesis of MNPs with controllable structural properties and various coatings to enhance their stability and functionality. This study describes a modified one-step method of coprecipitation in the presence of glycine allowing the production of particles with controllable size and in situ surface decoration. The effect of different glycine concentrations on the morphostructural and magnetic properties of iron oxide MNPs is studied. The particle size is reduced from 10.2 ± 0.3 to 7.2 ± 0.5 nm by increasing the glycine concentration from 0.06 up to 0.60 mol. The magnetic properties of obtained particles were tracked by SQUID magnetometry and Mossbauer spectroscopy. All samples of glycine capped iron oxide MNPs showed superparamagnetic behaviour at room temperature with maximal value of the saturation magnetization of 69 ± 4 Am2/kg. The results show the optimal concentration range of glycine which can be used in this method: a lower concertation than 0.15 mol does not affect the properties of obtained particles while higher concentrations than 0.3 mol lead to the reduction of magnetic properties (the saturation magnetisation reduces to 59 ± 3 Am2/kg when glycine concentration was 0.6 mol). The proposed economic and environment-friendly approach can be utilized to synthesise –NH2 functionalised MNPs for biomedical or wastewater treatment.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dubrovskiy A. A., Knyazev Yu. V., Velikanov D. A., Vorotynov A. M., Laptash N. M., Gerasimova Yu. V.
Заглавие : Giant anisotropy of magnetic properties of hydrated iron fluoridotitanate single crystal
Место публикации : J. Alloys Compd. - 2022. - Vol. 898. - Ст.162748. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2021.162748
Примечания : Cited References: 53. - The reported study was funded by Russian Foundation for Basic Research , Government of Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science according to the research project "Spectral and magnetic properties of single crystals of transition metal fluoride hexahydrates.” No. 20-42-240014
Аннотация: Study of the magnetic properties of the FeTiF6 ‧ 6 H2O single crystal has shown that this compound is a two-dimensional antiferromagnet with a Néеl temperature of TN = 8 K and its magnetic moment anisotropy attains 7000% at a temperature of T = 4.2 K. The Mössbauer spectroscopy data unambiguously indicate the paramagnetic state of iron cations in the temperature range of 4.2–300 K. However, a sharp change in the difference between the quadrupole doublet linewidths at 10 K has been observed, which is consistent with the temperature of magnetic ordering. It has been suggested that the long-range magnetic order is established in the crystal through the formation of the exchange coupling revealed by the electron spin resonance measurements on the oriented single crystals.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gerasimova Yu. V., Aleksandrovsky A. S., Laptash N. M., Gerasimov M. A., Krylov A. S., Vtyurin A. N., Dubrovskiy A. A.
Заглавие : Spectroscopy of structurally disordered hydrated iron fluoridotitanate in the regions of vibrational and electronic excitations
Место публикации : Spectrochim. Acta A. - 2022. - Vol. 264. - Ст.120244. - ISSN 13861425 (ISSN), DOI 10.1016/j.saa.2021.120244
Примечания : Cited References: 28. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory and Krasnoyarsk Regional Foundation of Science according to the research project “Spectral and magnetic properties of single crystals of transition metal fluoride hexahydrates.” No. 20-42-240014
Аннотация: Raman and optical absorption spectra of disordered hydrated iron fluoridotitanate (HITF) single crystal were studied. Temperature transformations of the Raman spectra indicate independent ordering processes of the [TiF6]2− and [Fe(H2O)6]2+ complexes below the structural phase transition. The absorption spectrum in the near-infrared and visible ranges includes transitions from the high spin ground state 5T2 of Fe2+ ion to the excited 5E state and a set of excited triplets. Analysis by Tanabe-Sugano method gives crystal field Dq = 490 cm−1 and Racah parameters B = 340 cm−1 and C = 1904 cm−1. Considerable decrease of B parameter as compared to the free ion value indicates a decrease of interelectron repulsion in the disordered neighborhood of Fe2+ ions.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dubrovskiy A. A., Knyazev Yu. V., Gerasimova Yu. V., Udovenko A. A., Laptash N. M.
Заглавие : Influence of the Jahn-Teller effect on magnetic anisotropy in single crystals of fluorine hexahydrates of transition metals
Место публикации : Phys. Solid State. - 2022. - Vol. 64, Is. 11. - P.1709-1712. - ISSN 10637834 (ISSN), DOI 10.21883/PSS.2022.11.54194.406. - ISSN 10906460 (eISSN)
Примечания : Cited References: 16. - The work was done with financial support from the Russian Foundation for Basic Research, Government of Krasnoyarsk Krai and the Krasnoyarsk Krai Foundation of Science within the research project No. 20-42-240014
Аннотация: The magnetic properties of fluorine hexahydrates of transition metals have been studied. It was found that the presence of spin-orbit interaction of the transition metal ion has a significant effect on anisotropy of magnetic properties. Depending on the direction of interaction of the orbital magnetic moment of a transition metal cation with a crystal field easy direction of magnetization changes from the crystallographic b-axis to the c-axis.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gerasimova Yu. V., Krylov A. S., Vtyurin A. N., Laptash N. M., Pogoreltsev E. I., Dubrovskiy A. A., Gerasimov M. A.
Заглавие : Dynamic processes of the water sublattice in FeTiF6·xH2O·yD2O crystal
Место публикации : J. Raman Spectrosc. - 2022. - Vol. 53, Is. 10: Special Issue: Vibrational Spectroscopy of Water. - P.1704-1709. - ISSN 03770486 (ISSN), DOI 10.1002/jrs.6430
Примечания : Cited References: 31. - The reported study was funded by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory and Krasnoyarsk Regional Foundation of Science according to the research project “Spectral and magnetic properties of single crystals of transition metal fluoride hexahydrates” No. 20-42-240014
Аннотация: Phase transition in FeTiF6·xH2O·yD2O crystals has been studied by Raman spectroscopy. The 611 cm-1 line corresponding to mode A1g of [TiF6]2- system does not exhibit anomalous behavior associated with the phase transition. The temperature studies showed that below the phase transition temperature, the equivalence of D2O molecules in FeTiF6·xH2O·yD2O octahedron is broken. The phase transition mechanism in the compound under study is associated with Fe(xH2O·yD2O) complex.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Ikkert O. P., Semenov S. V., Volochaev M. N., Molokeev M. S., Platunov M. S., Khramov E. V., Dubrovskiy A. A., Shestakov N. P., Smorodina E. D., Karnachuk O. V., Balaev D. A.
Заглавие : Superparamagnetic blocking and magnetic interactions in nanoferrihydrite adsorbed on biomineralized nanorod-shaped F3S4 crystallites
Место публикации : J. Alloys Compd. - 2022. - Vol. 923. - Ст.166346. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2022.166346
Примечания : Cited References: 109. - This study was supported by the Russian Science Foundation, project no. 22-24-00601 (https://rscf.ru/project/22–24–00601/)The electron microscopy and Mössbauer spectroscopy studies were carried out on the equipment of the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences. We thank Dr. Ivan Nemtsev for the SEM images. The contribution of M. P. (development of methodology of sample preparation for EXAFS measurements) was partially supported by the Russian Ministry of Science and Higher Education via the budget project of SRF SKIF, Boreskov Institute of Catalysis
Аннотация: A composite based on nanorod-shaped greigite (Fe3S4) crystallites with adsorbed ferrihydrite (Fe2O3 ‧ nH2O) nanoparticles has been synthesized. The synthesis has been performed by biomineralization of the bacterial wall of a sulfate-reducing Desulfovibrio sp. A2 bacteria. The phase composition of the synthesized composite has been investigated by X-ray powder and electron diffraction, as well as Fourier-transform infrared, extended X-ray absorption fine structure, and Mössbauer spectroscopy. The magnetic measurement data have shown that the sample under study contains two magnetic phases: multidomain nanorod-shaped greigite and ultrasmall ferrihydrite nanoparticles. The constant atomic fraction of the greigite crystalline phase in the range of 4–300 K (~20%) revealed by Mössbauer spectroscopy is indicative of a blocked magnetic moment of nanorod-shaped Fe3S4. It is shown that nanorod-shaped Fe3S4 crystallites are strongly magnetically bound with adsorbed Fe2O3 ‧ nH2O (Eint ~ 1200kB) nanoparticles. This significantly slows down the superparamagnetic relaxation of the magnetic moments of ferrihydrite nanoparticles. Therefore, the blocking temperature noticeably increases and attains, according to the Mössbauer spectroscopy data, a value of TB = 140 K (the magnetic measurements yield TB = 72 K). The processes of superparamagnetic blocking of the magnetic moments of ferrihydrite nanoparticles manifest themselves in the evolution of the magnetic properties of the investigated sample (a significant increase in the coercivity and remanent magnetization). In support of the Mössbauer spectroscopy data, a sufficiently high superparamagnetic blocking temperature has been established, which discloses the effect of magnetizing of ferrihydrite nanoparticles by coarser greigite formations, analogously to the effect of interparticle magnetic interactions.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Chumakov A. I., Dubrovskiy A. A., Semenov S. V., Sergueev I., Yakushkin S. S., Kirillov V. L., Martyanov O. N., Balaev D. A.
Заглавие : Nuclear forward scattering application to the spiral magnetic structure study in epsilon-Fe2O3
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [17-12-01111, SC-4708]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 9. - Ст.094408. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.094408. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 44. - We thank Dr. Natalia Kazak for assistance with the NFS measurements. This study was supported by the Russian Science Foundation, Project No. 17-12-01111. We thank the European Synchrotron Radiation Facility for provision of the synchrotron radiation facilities at the beamline ID18 (Exp. No. SC-4708)
Предметные рубрики: INCOMMENSURATE STRUCTURES
MOSSBAUER-SPECTROSCOPY
HIGH-TEMPERATURE
Аннотация: The ε−Fe2O3 magnetic structure has been analyzed using the synchrotron radiation source. Time spectra of nuclear forward scattering for isolated nanoparticles with an average size of 8 nm immobilized in a xerogel matrix have been recorded in the temperature range of 4–300K in applied magnetic fields of 0–4T in the longitudinal direction at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). It has been found that the external magnetic field does not qualitatively change the Hhf(T) behavior, but makes a strong opposite impact on the hyperfine fields in the nonequivalent iron sites, leading to the divergence of Hhf polar angle dependences below 80 K. A complete diagram of the ε−Fe2O3 magnetic structure in the temperature range of 4–300K is proposed. At 300 K, the ε−Fe2O3 compound is confirmed to be a collinear ferrimagnet. The experimental results show that the magnetic transition at 150–80K leads to the formation of a noncollinear magnetic structure. Furthermore, in the range of the 80–4 K, the ground state of a magnetic spiral is established. The experimental results are supplemented by the analysis of the exchange interactions and temperature dependence of the magnetization in a magnetic field of 7 T.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Popkov S. I., Dubrovskiy A. A., Semenov S. V., Velikanov D. A., Kirillov V. L., Martyanov O. N.
Заглавие : Features of the quasi-static and dynamic magnetization switching in NiO nanoparticles: Manifestation of the interaction between magnetic subsystems in antiferromagnetic nanoparticles
Место публикации : J. Magn. Magn. Mater. - 2020. - Vol. 515. - Ст.167307. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2020.167307
Примечания : Cited References: 89. - We are grateful to A.D. Balaev for fruitful discussions. The TEM study and magnetic measurements using a PPMS-6000 facility were carried out on the equipment of the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences
Аннотация: We report on the investigations of a system of 8-nm NiO particles representing antiferromagnetic (AFM) materials, which are weak magnetic in the form of submicron particles, but can be considered to be magnetoactive in the form of nanoparticles due to the formation of the uncompensated magnetic moment in them. The regularities of the behavior of magnetization switching in AFM nanoparticles are established by studying the magnetic hysteresis loops under standard quasi-static conditions and in a quasi-sinusoidal pulsed field of up to 130 kOe with pulse lengths of 4–16 ms. The magnetic hysteresis loops are characterized by the strong fields of the irreversible magnetization behavior, which is especially pronounced upon pulsed field-induced magnetization switching. Under the pulsed field-induced magnetization switching conditions, which are analogous to the dynamic magnetic hysteresis, the coercivity increases with an increase in the maximum applied field H0 and a decrease in the pulse length. This behavior is explained by considering the flipping of magnetic moments of particles in an external ac magnetic field; however, in contrast to the case of single-domain ferro- and ferrimagnetic particles, the external field variation rate dH/dt is not a universal parameter uniquely determining the coercivity. At the dynamic magnetization switching in AFM nanoparticles, the H0 value plays a much more important role. The results obtained are indicative of the complex dynamics of the interaction between magnetic subsystems formed in AFM nanoparticles.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yakushkin S. S., Bukhtiyarova G. A., Dubrovskiy A. A., Knyazev Yu. V., Balaev D. A., Martyanov O. N.
Заглавие : In Situ FMR Study of the Selective H2S-Oxidation Stability of ε-Fe2O3/SiO2 Catalysts
Коллективы : Russian Science Foundation [17-12-01111]
Место публикации : Appl. Magn. Reson. - 2019. - Vol. 50, Is. 5. - P.725-733. - ISSN 0937-9347, DOI 10.1007/s00723-019-1109-3. - ISSN 1613-7507(eISSN)
Примечания : Cited References:32. - This work was supported by the Russian Science Foundation, project no. 17-12-01111.
Предметные рубрики: HYDROGEN-SULFIDE
CALCINATION TEMPERATURE
OXIDATION
PHASE
BED
Аннотация: The stability of a catalyst for partial H2S oxidation has been studied by the ferromagnetic resonance (FMR) technique combined with transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and magnetostatic investigations. The ε-Fe2O3 iron oxide nanoparticles supported on silica have been examined for their stability under the selective H2S oxidation conditions. The combination of the physicochemical methods has been used to study the state of reacted catalysts. The ε-Fe2O3 phase has been found to remain stable under the selective H2S oxidation conditions at temperatures up to 300 °C. The active phase state during the catalytic reaction has been explored using in situ FMR experiments. It has been established that the ε-Fe2O3 nanoparticles retain their structure and magnetic properties in the presence of H2S at high temperatures. During the in situ FMR experiments, the ε-Fe2O3 sulfidation process has been studied.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Yakushkin S. S., Bukhtiyarova G. A., Martyanov O. N.
Заглавие : Temperature of the Magnetic Ordering of the Trivalent Iron Oxide ε-Fe2O3
Место публикации : Phys. Solid State. - 2019. - Vol. 61, Is. 3. - P.345-349. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783419030053
Примечания : Cited References: 39. - This study was supported by the Russian Science Foundation, project no. 17-12-01111.
Аннотация: The trivalent iron oxide ε-Fe2O3 is a fairly rare polymorphic iron oxide modification, which only exists in the form of nanoparticles. This magnetically ordered material exhibits an intriguing magnetic behavior, specifically, a significant room-temperature coercivity HC (up to ~20 kOe) and a magnetic transition in the temperature range of 80–150 K accompanied by a sharp decrease in the HC value. Previously, the temperature of the transition to the paramagnetic state for ε-Fe2O3 was believed to be about 500 K. However, recent investigations have shown that the magnetically ordered phase exists in ε-Fe2O3 also at higher temperatures and, around 500 K, another magnetic transition occurs. Using the data on the magnetization and temperature evolution of the ferromagnetic resonance spectra, it is shown that the temperature of the transition of ε-Fe2O3 particles 3–10 nm in size to the paramagnetic state is ~850 K.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Балаев, Дмитрий Александрович, Дубровский, Андрей Александрович, Якушкин С. С., Бухтиярова Г. А., Мартьянов О. Н.
Заглавие : Температура магнитного упорядочения оксида трехвалентного железа ε-Fe2O3
Место публикации : Физ. тверд. тела. - 2019. - Т. 61, Вып. 3. - С. 478-482. - ISSN 0367-3294, DOI 10.21883/FTT.2019.03.47239.277
Примечания : Библиогр.: 38. - Работа выполнена при поддержке Российского научного фонда, грант N 17-12-01111.
Аннотация: Оксид трехвалентного железа ε-Fe2O3 является достаточно редкой полиморфной модификацией оксида железа и существует только в виде наночастиц. Этот магнитоупорядоченный материал демонстрирует интересное магнитное поведение: значительную коэрцитивную силу HC при комнатной температуре (до ~ 20 kOe), магнитный переход в температурном диапазоне 80-150 K, сопровождающийся резким уменьшением величины HC. Ранее считалось, что температура перехода в парамагнитное состояние для ε-Fe2O3 составляет около 500 K. Однако недавние исследования показали, что магнитоупорядоченная фаза в ε-Fe2O3 существует до более высоких температур, и при этом в окрестности 500 K происходит ещё один магнитный переход. В настоящей работе на основании данных по намагниченности и температурной эволюции спектров ферромагнитного резонанса показано, что температура перехода в парамагнитное состояние для частиц ε-Fe2O3 размерами 3-10 nm составляет ~850 K.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Dubrovskiy A. A., Balaev A. D., Popkov S. I., Kirillov V. L., Martyanov O. N.
Заглавие : Dynamic magnetization switching in NiO nanoparticles: Pulsed field magnetometry study
Место публикации : J. Supercond. Novel Magn. - 2019. - Vol. 32, Is. 2. - P.405–411. - ISSN 15571939 (ISSN), DOI 10.1007/s10948-018-4726-4
Примечания : Cited References: 32. - We are grateful to Yu.V. Knyazev, S.V. Semenov, and M.I. Kolkov for their help and to M.N. Volochaev for the TEM measurements. TEM studies were performed on the facility of Resource Sharing Center of Krasnoyarsk Scientific Center of Siberian Branch of Russian Academy of Sciences.The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project no. 17-42-240138.
Ключевые слова (''Своб.индексиров.''): nio nanoparticles--pulsed field magnetization--coercivity
Аннотация: The dynamic magnetization switching of antiferromagnetic nickel oxide nanoparticles with a characteristic size of 8 nm has been experimentally investigated by pulsed field magnetometry. It is shown that, due to the presence of defects in NiO nanoparticles, as in other antiferromagnetic particles, the uncompensated magnetic moment is induced by the incomplete compensation of spins at the antiferromagnetic ordering. The dynamic magnetic hysteresis loops have been studied in pulsed fields with the maximum field (Hmax) of up to 130 kOe and pulse lengths (τP) of 4, 8, and 16 ms. According to the results obtained, the coercivity (HC) depends on both the τP and Hmax values. The observed increase in the HC value with decreasing pulse length (i.e., with increasing switching field frequency) is unambiguously related with the relaxation processes typical of single-domain ferromagnetic nanoparticles. However, the observed effect of the maximum applied field (Hmax) on the HC value is assumed to be a feature of antiferromagnetic nanoparticles.
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