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    Magnetic Hysteresis of Blocked Ferrihydrite Nanoparticles / S. Komogortsev, D. Balaev, A. Krasikov, S. Stolyar, R. Yaroslavtsev, V. Ladygina and R. Iskhakov // 65th Annual conference on мagnetism and мagnetic мaterials (MMM-2020) : abstract book. - 2020. - Ст. C4-02. - P. 74
   Перевод заглавия: Высоко-индукционные пленки FeCo: Зеленый синтез и магнитные свойства

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Доп.точки доступа:
Komogortsev, S. V.; Комогорцев, Сергей Викторович; Balaev, D. A.; Балаев, Дмитрий Александрович; Krasikov, A. A.; Красиков, Александр Александрович; Stolyar, S. V.; Столяр, Сергей Викторович; Yaroslavtsev, R. N.; Ярославцев, Роман Николаевич; Iskhakov, R. S.; Исхаков, Рауф Садыкович; Annual conference on мagnetism and мagnetic мaterials(65 ; 2020 ; 2-6 Nov. ; Virtual Conference)
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Magnetic hysteresis of blocked ferrihydrite nanoparticles / S. V. Komogortsev, D. A. Balaev, A. A. Krasikov [et al.] // AIP Adv. - 2021. - Vol. 11, Is. 1. - Ст. 015329, DOI 10.1063/9.0000111. - Cited References: 23. - The magnetic measurements were partially carried out on the equipment of the Krasnoyarsk Regional Center for Collective Use, Krasnoyarsk Science Center, Siberian Branch, Russian Academy of Sciences. This study was supported by the Council of the President of the Russian Federation for State Support of Young Scientists and Leading Scientific Schools (project no. MK-1263.2020.3) . - ISSN 2158-3226
Кл.слова (ненормированные):
Hysteresis -- Hysteresis loops -- Magnetic anisotropy -- Magnetic materials -- Nanoparticles -- Anisotropy field -- Ferrihydrites -- Field amplitudes -- Magnetic anisotropy field -- Minor hysteresis loop -- Stoner-Wohlfarth model -- Uniaxial anisotropy -- Nanomagnetics
Аннотация: Using minor hysteresis loops in the Stoner-Wohlfarth model allows describing the experimental behavior of the coercive force of minor hysteresis loops in ferrihydrite nanoparticles with a change in the field amplitude. The description allows estimating the parameters of the distribution of the magnetic anisotropy field in nanoparticles. The best agreement of the anisotropy fields estimated by different approaches is achieved for the assumption of uniaxial anisotropy in ferrihydrite nanoparticles.

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Держатели документа:
Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, 660036, Russian Federation
Krasnoyarsk Science Center, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Komogortsev, S. V.; Комогорцев, Сергей Викторович; Balaev, D. A.; Балаев, Дмитрий Александрович; Krasikov, A. A.; Красиков, Александр Александрович; Stolyar, S. V.; Yaroslavtsev, R. N.; Ladygina, V. P.; Iskhakov, R. S.; Исхаков, Рауф Садыкович
}
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Общие закономерности и различия в поведении динамического перемагничивания ферримагнитных (CoFe2O4) и антиферромагнитных (NiO) наночастиц / С. И. Попков, А. А. Красиков, С. В. Семенов [и др.] // Физ. тверд. тела. - 2020. - Т. 62, Вып. 9. - С. 1354-1360, DOI 10.21883/FTT.2020.09.49753.25H. - Библиогр.: 46. - Исследование выполнено при финансовой поддержке Российского фонда фундаментальных исследований, Правительства Красноярского края, Красноярского краевого фонда науки в рамках научного проекта No 18-42-240012: ”Перемагничивание магнитных наночастиц в сильных импульсных магнитных полях — новый подход к исследованию динамических эффектов, связанных с процессами намагничивания магнитных наночастиц“ . - ISSN 0367-3294
Кл.слова (ненормированные):
наночастицы CoFe2O4 -- антиферромагнитные наночастицы NiO -- динамическое перемагничивание -- коэрцитивная сила
Аннотация: В наноразмерных антиферромагнитных (АФМ) частицах формируется дополнительная ферромагнитная (ФМ) подсистема, приводя к возникновению у АФМ-наночастиц нескомпенсированного магнитного момента и магнитных свойств, типичных для обычных ФМ-наночастиц. Для выявления закономерностей и различий динамического перемагничивания ФМ- и АФМ-наночастиц в настоящей работе исследованы типичные представители таких материалов: наночастицы CoFe2O4 и NiO средними размерами 6 и 8 nm соответственно. Большие величины полей необратимого поведения намагниченности этих образцов определяют необходимость использования сильных импульсных полей (амплитудой до 130 kOe) для исключения влияния эффекта частной петли гистерезиса при исследованиях динамического магнитного гистерезиса. Для образцов обоих типов коэрцитивная сила HC при динамическом перемагничивании заметно превосходит HC при квазистатических условиях. HC возрастает с уменьшением длительности импульса tauP и при увеличении максимального приложенного поля H0. Зависимость HC от скорости изменения поля dH/dt=H0/2τP является однозначной функцией для наночастиц CoFe2O4, и именно такое поведение ожидается от системы однодоменных ФМ-наночастиц. В то же время для АФМ-наночастиц NiO коэрцитивная сила уже не является однозначной функцией dH/dt, и большее влияние оказывает величина приложенного поля H0. Такое различие в поведении ФМ- и АФМ-наночастиц вызвано взаимодействием ФМ-подсистемы и АФМ-"ядра" внутри АФМ-наночастицы. Указанное обстоятельство необходимо учитывать при построении теории динамического гистерезиса АФМ-наночастиц и принимать во внимание при их практическом применении.

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Переводная версия General regularities and differences in the behavior of the dynamic magnetization switching of ferrimagnetic (CoFe2O4) and antiferromagnetic (NiO) nanoparticles [Текст] / S. I. Popkov, A. A. Krasikov, S. V. Semenov [et al.] // Phys. Solid State. - 2020. - Vol. 62 Is. 9.- P.1518-1524

Держатели документа:
Институт физики им. Л.В. Киренского Сибирского отделения Российской академии наук, Красноярск, Россия
Сибирский федеральный университет, Красноярск, Россия
Институт катализа им. Г.К. Борескова СО РАН, Новосибирск, Россия

Доп.точки доступа:
Попков, Сергей Иванович; Popkov, S. I.; Красиков, Александр Александрович; Krasikov, A. A.; Семенов, Сергей Васильевич; Semenov, S. V.; Дубровский, Андрей Александрович; Dubrovskii, A. A.; Якушкин, С. С.; Кириллов, В. Л.; Мартьянов, О. Н.; Балаев, Дмитрий Александрович; Balaev, D. A.
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Features of the quasi-static and dynamic magnetization switching in NiO nanoparticles: Manifestation of the interaction between magnetic subsystems in antiferromagnetic nanoparticles / D. A. Balaev, A. A. Krasikov, S. I. Popkov [et al.] // J. Magn. Magn. Mater. - 2020. - Vol. 515. - Ст. 167307, DOI 10.1016/j.jmmm.2020.167307. - 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 . - ISSN 0304-8853
Кл.слова (ненормированные):
Antiferromagnetic nanoparticle -- Dynamic magnetization -- Irreversible magnetization -- Magnetic subsystems -- Magnetization switching -- Quasi-static conditions -- Sub-micron particles -- Universal parameters
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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Держатели документа:
Kirensky Institute of Physics, Federal Research Center “Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences”, Krasnoyarsk, 660036, Russian Federation
Siberian Federal University, Krasnoyarsk, 660041, Russian Federation
Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russian Federation

Доп.точки доступа:
Balaev, D. A.; Балаев, Дмитрий Александрович; Krasikov, A. A.; Красиков, Александр Александрович; Popkov, S. I.; Попков, Сергей Иванович; Dubrovskiy, A. A.; Дубровский, Андрей Александрович; Semenov, S. V.; Семёнов, Сергей Васильевич; Velikanov, D. A.; Великанов, Дмитрий Анатольевич; Kirillov, V. L.; Martyanov, O. N.
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General regularities and differences in the behavior of the dynamic magnetization switching of ferrimagnetic (CoFe2O4) and antiferromagnetic (NiO) nanoparticles / S. I. Popkov, A. A. Krasikov, S. V. Semenov [et al.] // Phys. Solid State. - 2020. - Vol. 62, Is. 9. - P. 1518-1524, DOI 10.1134/S1063783420090255. - Cited References: 46. - This work was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk region, and the Krasnoyarsk Regional Foundation for Science, project no. 18-42-240012: "Magnetization switching of magnetic nanoparticles in strong pulsed magnetic fields is a new approach to studying the dynamic effects related to the processes of magnetization of magnetic nanoparticles" . - ISSN 1063-7834. - ISSN 1090-6460

РУБ Physics, Condensed Matter
Рубрики:
PARTICLE-SIZE
   EXCHANGE-BIAS
   TEMPERATURE
   STATE
   COERCIVITY
Кл.слова (ненормированные):
CoFe2O4nanoparticles -- antiferromagnetic NiO nanoparticles -- dynamic magnetization switching -- coercive force
Аннотация: In antiferromagnetic (AFM) nanoparticles, an additional ferromagnetic phase forms and leads to the appearance in AFM nanoparticles of a noncompensated magnetic moment and the magnetic properties typical of common FM nanoparticles. In this work, to reveal the regularities and differences of the dynamic magnetization switching in FM and AFM nanoparticles, the typical representatives of such materials are studied: CoFe2O4 and NiO nanoparticles with average sizes 6 and 8 nm, respectively. The high fields of the irreversible behavior of the magnetizations of these samples determine the necessity of using strong pulsed fields (amplitude to 130 kOe) to eliminate the effect of the partial hysteresis loop when studying the dynamic magnetic hysteresis. For both types of the samples, coercive force HC at the dynamic magnetization switching is markedly higher than HC at quasi-static conditions. HC increases as the pulse duration τP decreases and the maximum applied field H0 increases. The dependence of HC on field variation rate dH/dt = H0/2τP is a unambiguous function for CoFe2O4 nanoparticles, and it is precisely such a behavior is expected from a system of single-domain FM nanoparticles. At the same time, for AFM NiO nanoparticles, the coercive force is no longer an unambiguous function of dH/dt, and the value of applied field H0 influences more substantially. Such a difference in the behaviors of FM and AFM nanoparticles is caused by the interaction of the FM subsystem and the AFM “core” inside AFM nanoparticles. This circumstance should be taken into account when developing the theory of dynamic hysteresis of the AFM nanoparticles and also to take into account their practical application.

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Публикация на русском языке Общие закономерности и различия в поведении динамического перемагничивания ферримагнитных (CoFe2O4) и антиферромагнитных (NiO) наночастиц [Текст] / С. И. Попков, А. А. Красиков, С. В. Семенов [и др.] // Физ. тверд. тела. - 2020. - Т. 62 Вып. 9. - С. 1354-1360

Держатели документа:
Russian Acad Sci, Siberian Branch, Krasnoyarsk Sci Ctr, Kirensky Inst Phys, Krasnoyarsk 660036, Russia.
Siberian Fed Univ, Krasnoyarsk 660041, Russia.
Russian Acad Sci, Boreskov Inst Catalisis, Siberian Branch, Novosibirsk 630090, Russia.

Доп.точки доступа:
Popkov, S. I.; Попков, Сергей Иванович; Krasikov, A. A.; Красиков, Александр Александрович; Semenov, S. V.; Семёнов, Сергей Васильевич; Dubrovskii, A. A.; Дубровский, Андрей Александрович; Yakushkin, S. S.; Kirillov, V. L.; Mart'yanov, O. N.; Balaev, D. A.; Балаев, Дмитрий Александрович; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk region; Krasnoyarsk Regional Foundation for Science [18-42-240012]
}
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Biogenic ferrihydrite nanoparticles: Synthesis, properties in vitro and in vivo testing and the concentration effect / S. V. Stolyar, O. A. Kolenchukova, A. V. Boldyreva [et al.] // Biomedicines. - 2021. - Vol. 9, Is. 3. - Ст. 323, DOI 10.3390/biomedicines9030323. - Cited References: 52. - This research was funded by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory and the Regional Science Foundation, grant number 20-416-242907 . - ISSN 2227-9059

РУБ Biochemistry & Molecular Biology + Medicine, Research & Experimental + Pharmacology & Pharmacy

Кл.слова (ненормированные):
ferrihydrite nanoparticles -- concentration effect -- microorganisms Klebsiella oxytoca -- neutrophilic granulocytes -- chemiluminescence -- toxicology
Аннотация: Biogenic ferrihydrite nanoparticles were synthesized as a result of the cultivation of Klebsiella oxytoca microorganisms. The distribution of nanoparticles in the body of laboratory animals and the physical properties of the nanoparticles were studied. The synthesized ferrihydrite nanoparticles are superparamagnetic at room temperature, and the characteristic blocking temperature is 23-25 K. The uncompensated moment of ferrihydrite particles was determined to be approximately 200 Bohr magnetons. In vitro testing of different concentrations of ferrihydrite nanoparticles for the functional activity of neutrophilic granulocytes by the chemiluminescence method showed an increase in the release of primary oxygen radicals by blood phagocytes when exposed to a minimum concentration and a decrease in secondary radicals when exposed to a maximum concentration. In vivo testing of ferrihydrite nanoparticles on Wister rats showed that a suspension of ferrihydrite nanoparticles has chronic toxicity, since it causes morphological changes in organs, mainly in the spleen, which are characterized by the accumulation of hemosiderin nanoparticles (stained blue according to Perls). Ferrihydrite can also directly or indirectly stimulate the proliferation and intracellular regeneration of hepatocytes. The partial detection of Perls-positive cells in the liver and kidneys can be explained by the rapid elimination from organs and the high dispersion of the nanomaterial. Thus, it is necessary to carry out studies of these processes at the systemic level, since the introduction of nanoparticles into the body is characterized by adaptive-proliferative processes, accompanied by the development of cell dystrophy and tension of the phagocytic system.

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Держатели документа:
RAS, Kirensky Inst Phys, Fed Res Ctr KSC SB, Krasnoyarsk 660036, Russia.
RAS, Krasnoyarsk Sci Ctr, Fed Res Ctr KSC SB, Krasnoyarsk 660036, Russia.
Siberian Fed Univ, Dept Biophys, Krasnoyarsk 660041, Russia.
RAS, Sci Res Inst Med Problems North, Fed Res Ctr KSC SB, Krasnoyarsk 660022, Russia.
RAS, Inst Biophys, Fed Res Ctr KSC SB, Krasnoyarsk 660036, Russia.

Доп.точки доступа:
Stolyar, S. V.; Столяр, Сергей Викторович; Kolenchukova, Oksana A.; Boldyreva, Anna V.; Kudryasheva, Nadezda S.; Gerasimova, Yu. V.; Герасимова, Юлия Валентиновна; Krasikov, A. A.; Красиков, Александр Александрович; Yaroslavtsev, R. N.; Ярославцев, Роман Николаевич; Bayukov, O. A.; Баюков, Олег Артемьевич; Ladygina, Valentina P.; Birukova, Elena A.; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk Territory; Regional Science Foundation [20-416-242907]
}
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Superparamagnetic effect on the dynamic remagnetization of CoFe2O4 nanoparticles in a pulse field / D. A. Balaev, I. S. Poperechny, A. A. Krasikov [et al.] // 4th International Baltic Conference on Magnetism (IBCM 2021) : Book of abstracts. - 2021. - P. 104. - Cited References: 7

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS

Доп.точки доступа:
Balaev, D. A.; Балаев, Дмитрий Александрович; Poperechny, I. S.; Krasikov, A. A.; Красиков, Александр Александрович; Semenov, S. V.; Семёнов, Сергей Васильевич; Popkov, S. I.; Попков, Сергей Иванович; Knyazev, Yu. V.; Князев, Юрий Владимирович; Kirillov, V. L.; Yakushkin, S. S.; Martyanov, O.; Raikher, Y. L.; International Baltic Conference on Magnetism: focus on nanobiomedicine and smart materials(4 ; 2021 ; Aug. 29-Sept. 2 ; Svetlogorsk, Russia); Балтийский федеральный университет им. И. Канта
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Role of the surface effects and interparticle magnetic interactions in the temperature evolution of magnetic resonance spectra of ferrihydrite nanoparticle ensembles / D. A. Balaev, S. V. Stolyar, Y. V. Knyazev [et al.] // Results Phys. - 2022. - Vol. 35. - Ст. 105340, DOI 10.1016/j.rinp.2022.105340. - Cited References: 119. - Authors thank to A.D. Balaev, S.V. Komogortsev for fruitful discussions and M.N. Volochaev for TEM studies. The TEM study and measurements of X-band FMR spectra were carried out on the equipment of the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences. This study was supported by the Russian Science Foundation, project no. 21-72-00025 (https://rscf.ru/project/21-72-00025/) "Tuning the Magnetic Properties of Ultrafine Biocompatible Ferrihydrite Nanoparticles through Interparticle Interactions" . - ISSN 2211-3797
Кл.слова (ненормированные):
Ferrihydrite nanoparticles -- Superparamagnetism -- Interparticle magnetic interactions -- Ferromagnetic resonance
Аннотация: Ferrihydrite is characterized by the antiferromagnetic ordering and, in ferrihydrite nanoparticles, as in nanoparticles of any antiferromagnetic material, an uncompensated magnetic moment is formed. We report on the investigations of ferrihydrite powder systems with an average particle size of ∼ 2.5 nm obtained (i) as a product of the vital activity of bacteria (sample FH-bact) and (ii) by a chemical method (sample FH-chem). In the first approximation, these samples can be considered to be identical. However, in sample FH-chem, particles contact directly, while in sample FH-bact, they have organic shells; therefore, the interparticle magnetic interactions in these samples have different degrees. The main goal of this work has been to establish the effects of the interparticle magnetic interactions and individual characteristics of ferrihydrite nanoparticles on ferromagnetic resonance (FMR) spectra. The FMR spectra have been measured at different (9.4–75 GHz) frequencies in a wide temperature range. It has been found that, at low temperatures, the field-frequency dependence ν(HR) of the investigated systems has a gap ν/γ = HR + HA, where HR is the resonance field and HA is the induced anisotropy, which decreases with increasing temperature. To estimate a degree of the effect of interparticle interactions on the results obtained and to correctly determine the temperature range of the superparamagnetic (or blocked) state, the static magnetic measurement and Mössbauer spectroscopy data have been obtained and analyzed. It has been shown that the most striking feature of the FMR spectra - a gap in the field-frequency dependences - is a manifestation of individual characteristics of ferrihydrite nanoparticles. The induced anisotropy is caused by freezing of a subsystem of surface spins and its coupling with the particle core, which is observed in both samples at a temperature of ∼80 K. The temperature range (below 80 K) in which the gap exists corresponds to the blocked state in the FMR technique. In sample FH-bact, the ratio between the FMR parameters HA and linewidth ΔH obeys the standard expression HA ∼ (ΔH)3. In sample FH-chem, however, the interparticle magnetic interactions dramatically affect the behavior of parameters of the FMR spectra, which change nonmonotonically upon temperature variation. This fact is attributed to the collective freezing of the magnetic moments of particles under the conditions of sufficiently strong interactions, which follows from the temperature dependence of the particle magnetic moment relaxation time determined from the Mössbauer spectroscopy and static magnetometry data obtained in weak magnetic fields.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Akademgorodok 50, bld. 38, Krasnoyarsk, 660036, Russian Federation
Siberian Federal University, Svobodniy 79, Krasnoyarsk, 660041, Russian Federation
Krasnoyarsk Scientific Center, Federal Research Center KSC SB RAS, Akademgorodok 50, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Balaev, D. A.; Балаев, Дмитрий Александрович; Stolyar, S. V.; Столяр, Сергей Викторович; Knyazev, Yu. V.; Князев, Юрий Владимирович; Yaroslavtsev, R. N.; Ярославцев, Роман Николаевич; Pankrats, A. I.; Панкрац, Анатолий Иванович; Vorotynov, A. M.; Воротынов, Александр Михайлович; Krasikov, A. A.; Красиков, Александр Александрович; Velikanov, D. A.; Великанов, Дмитрий Анатольевич; Bayukov, O. A.; Баюков, Олег Артемьевич; Ladygina, V. P.; Iskhakov, R. S.; Исхаков, Рауф Садыкович
}
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Interparticle magnetic interactions in synthetic ferrihydrite: Mossbauer spectroscopy and magnetometry study of the dynamic and static manifestations / Y. V. Knyazev, D. A. Balaev, S. V. Stolyar [et al.] // J. Alloys Compd. - 2022. - Vol. 889. - Ст. 161623, DOI 10.1016/j.jallcom.2021.161623. - Cited References: 84. - This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory, and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project no. 19–42–240012 R-A “Magnetic Resonance in Ferrihydrite Nanoparticles: Effects Related to the Core-Shell Structure” . - ISSN 0925-8388
Кл.слова (ненормированные):
Ferrihydrite nanoparticles -- Superparamagnetism -- Interparticle magnetic interactions
Аннотация: Samples of synthetic ferrihydrite with an average nanoparticle size of 2.7 nm have been examined by magnetometry and Mossbauer spectroscopy. Ferrihydrite is characterized by the antiferromagnetic interactions between the magnetic moments of iron atoms. In ferrihydrite nanoparticles, as in any other antiferromagnetic ones, structural defects induce the formation of an uncompensated magnetic moment, which determines the magnetic properties typical of single-domain ferro- and ferrimagnetic particles. The manifestation of the magnetic interactions between ferrihydrite nanoparticles in the magnetic properties of the material and in the temperature evolution of Mossbauer spectra has been in focus. The results obtained on synthetic ferrihydrite have been compared with the data for the biogenic ferrihydrite sample with a similar average size of particles surrounded by a polysaccharide shell, which weakens and screens the interparticle magnetic interactions. A clear manifestation of the effect of the interparticle magnetic interactions on the transition to the blocked state is the presence of a significant contribution of the relaxation component in the Mossbauer spectra at temperatures of the transition from the superparamagnetic to blocked state. The temperature dependence of the particle relaxation time obtained from the Mossbauer spectra points out the collective effect of freezing of the magnetic moments of particles due to the magnetic interactions between them.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Akademgorodok 50, bld. 38, Krasnoyarsk, 660036, Russian Federation
Siberian Federal University, Svobodniy 79, Krasnoyarsk, 660041, Russian Federation
Krasnoyarsk Scientific Center, Federal Research Center KSC SB RAS, Akademgorodok 50, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Knyazev, Yu. V.; Князев, Юрий Владимирович; Balaev, D. A.; Балаев, Дмитрий Александрович; Stolyar, S. V.; Столяр, Сергей Викторович; Krasikov, A. A.; Красиков, Александр Александрович; Bayukov, O. A.; Баюков, Олег Артемьевич; Volochaev, M. N.; Волочаев, Михаил Николаевич; Yaroslavtsev, R. N.; Ярославцев, Роман Николаевич; Ladygina, V. P.; Velikanov, D. A.; Великанов, Дмитрий Анатольевич; Iskhakov, R. S.; Исхаков, Рауф Садыкович
}
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10.

Dynamic remagnetisation of CoFe2O4 nanoparticles: thermal fluctuational thawing of anisotropy / D. A. Balaev, I. S. Poperechny, A. A. Krasikov [et al.] // J. Phys. D. - 2021. - Vol. 54, Is. 27. - Ст. 275003, DOI 10.1088/1361-6463/abf371. - Cited References: 63. - Experimental measurements were supported by Project No. AAAA-A17-117103050081-1. I S P and Yu L R acknowledge the support of ICMM in the framework of topical task AAAAA20-120020690030-5. The numerical calculations were performed on the Uran supercomputer (Ural Branch, Russian Academy of Sciences, Ekaterinburg) . - ISSN 0022-3727. - ISSN 1361-6463

РУБ Physics, Applied
Рубрики:
COBALT-FERRITE NANOPARTICLES
   MAGNETIC-PROPERTIES
   SIZE
   COERCIVITY
Кл.слова (ненормированные):
nanoparticles -- cobalt ferrite -- magnetodynamics -- superparamagnetism -- effective anisotropy
Аннотация: We report a study of the magnetodynamics of cobalt ferrite (CoFe2O4) nanoparticles with an average diameter of ~6 nm. Hysteresis loops were measured under quasi-static conditions and in pulse fields with amplitudes H0 of up to 130 kOe and for durations τP of 8 and 16 ms. The growth of coercivity Hc observed with an increase in the magnetic field variation rate dH/dt (determined by the values of H0 and τP) and the reduction of Hc with temperature is ascribed to the superparamagnetic effect. The proposed theoretical model explains the observed dependences fairly well. Notably, the effective magnetic anisotropy constant obtained exceeds the value for bulk crystals and might be indicative of the contribution of surface magnetic anisotropy.

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Держатели документа:
Russian Acad Sci, Inst Phys, Siberian Branch, Krasnoyarsk 660000, Russia.
Russian Acad Sci, Inst Continuous Media Mech, Ural Branch, Perm 614068, Russia.
Perm State Natl Res Univ, Dept Phase Transit Phys, Perm 614990, Russia.
Russian Acad Sci, Boreskov Inst Catalysis, Siberian Branch, Novosibirsk 630090, Russia.

Доп.точки доступа:
Balaev, D. A.; Балаев, Дмитрий Александрович; Poperechny, I. S.; Krasikov, A. A.; Красиков, Александр Александрович; Semenov, S. V.; Семёнов, Сергей Васильевич; Popkov, S. I.; Попков, Сергей Иванович; Knyazev, Yu. V.; Князев, Юрий Владимирович; Kirillov, V. L.; Yakushkin, S. S.; Martyanov, O. N.; Raikher, Y. L.; [AAAA-A17-117103050081-1]; [AAAAA20-120020690030-5]
}
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