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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Stolyar S. V., Balaev D. A., Ladygina V. P., Dubrovskiy A. A., Krasikov A. A., Popkov S. I., Bayukov O. A., Knyazev Yu. V., Yaroslavtsev R. N., Volochaev M. N., Iskhakov R. S., Dobretsov K. G., Morozov E. V., Falaleev O. V., Inzhevatkin E. V., Kolenchukova O. A., Chizhova I. A.
Заглавие : Bacterial ferrihydrite nanoparticles: preparation, magnetic properties, and application in medicine
Место публикации : J. Supercond. Novel Magn. - 2018. - Vol. 31, Is. 8. - P.2297-2304. - ISSN 15571939 (ISSN), DOI 10.1007/s10948-018-4700-1
Примечания : Cited References: 37. - The electron microscopy examination was carried out at the Center for Collective Use of the Krasnoyarsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences (Krasnoyarsk, Russia).
Ключевые слова (''Своб.индексиров.''): nanoparticles--ferrihydrite--magnetic properties--drug delivery
Аннотация: Nanoparticles of antiferromagnetically ordered materials acquire the uncompensated magnetic moment caused by defects and surface effects. A bright example of such a nano-antiferromagnet is nanoferrihydrite consisting of particles 2–5 nm in size, the magnetic moment of which amounts to hundreds of Bohr magnetons per particle. We present a brief review of the studies on magnetic properties of ferrihydrite produced by bacteria. Special attention is focused on the aspects of possible biomedical applications of this material, i.e., the particle elimination, toxicity, and possible use for targeted drug delivery.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Stolyar S. V., Balaev D. A., Ladygina V. P., Dubrovskiy A. A., Krasikov A. A., Popkov S. I., Bayukov O. A., Yaroslavtsev R. N., Volochaev M. N., Iskhakov R. S., Dobretsov K. G., Falaleev O.V., Chizhova I. A.
Заглавие : Bacterial ferrihydrite nanoparticles: preparation, magnetic properties, and application in medicine
Коллективы : Moscow International Symposium on Magnetism, Московский государственный университет им. М.В. Ломоносова, Российский фонд фундаментальных исследований
Место публикации : Moscow Int. Symp. on Magnet. (MISM-2017): 1-7 July 2017 : book of abstracts. - 2017. - Ст.3RP-O-10. - P.417
Примечания : Cited References: 8. - Support by the Special Program for Siberian Federal University of the Ministry of Education and Science of the Russian Federation is acknowledged
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Stolyar S. V., Kolenchukova, Oksana A., Boldyreva, Anna V., Kudryasheva, Nadezda S., Gerasimova Yu. V., Krasikov A. A., Yaroslavtsev R. N., Bayukov O. A., Ladygina, Valentina P., Birukova, Elena A.
Заглавие : Biogenic ferrihydrite nanoparticles: Synthesis, properties in vitro and in vivo testing and the concentration effect
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk Territory; Regional Science Foundation [20-416-242907]
Место публикации : Biomedicines. - 2021. - Vol. 9, Is. 3. - Ст.323. - ISSN 2227-9059(eISSN), DOI 10.3390/biomedicines9030323
Примечания : 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
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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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Freydman A. L., Popkov S. I., Krasikov A. A., Mikhashenok N. V.
Заглавие : Capacitance dilatometer for small deformations measurements caused by external magnetic and electric fields and temperature
Коллективы : Moscow International Symposium on Magnetism, Московский государственный университет им. М.В. Ломоносова, Российский фонд фундаментальных исследований
Место публикации : Moscow International Symposium on Magnetism (MISM-2017): 1-7 July 2017 : book of abstracts. - 2017. - Ст.5PO-I2-2. - P.1047 (Шифр 29916280)
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Stolyar S. V., Iskhakov R. S., Ladygina V. P., Yaroslavtsev R. N., Bayukov O. A., Vorotynov A. M., Volochaev M. N., Dubrovskiy A. A.
Заглавие : Change in the magnetic properties of nanoferrihydrite with an increase in the volume of nanoparticles during low-temperature annealing
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 58, Is. 9. - P.1782-1791. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783416090092
Примечания : Cited References: 32. - This study was supported by the Ministry of Education and Science of the Russian Federation within the State Task for 2014-2016.
Предметные рубрики: FERRIHYDRITE NANOPARTICLES
BACTERIAL FERRIHYDRITE
FERRITIN
HYSTERESIS
MOSSBAUER
ORIGIN
Аннотация: The results of the investigation into the effect of low-temperature annealing of a powder of nanoparticles of bacterial ferrihydrite on its magnetic properties have been presented. It has been found that an increase in the time (up to 240 h) and temperature (in the range from 150 to 200°C) of annealing leads to a monotonic increase in the superparamagnetic blocking temperature, the coercive force, and the threshold field of the opening of the magnetic hysteresis loop (at liquid-helium temperatures), as well as to an increase in the magnetic resonance line width at low temperatures and in the magnetic susceptibility at room temperature. At the same time, according to the results of the analysis of the Mossbauer spectra, the annealing of ferrihydrite does not lead to the formation of new iron oxide phases. Most of these features are well consistent with the fact that the low-temperature annealing of ferrihydrite causes an increase in the size of nanoparticles, which is confirmed by the results of transmission electron microscopy studies. © 2016, Pleiades Publishing, Ltd.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gokhfel'd D. M., Semenov S. V., Balaev D. A., Dubrovskiy A. A., Terent'yev K. Yu., Freydman A. L., Krasikov A. A., Petrov M. I.
Заглавие : Control of peak effect in YBCO by Nd substitution
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : VI Euro-Asian Symposium "Trends in MAGnetism" (EASTMAG-2016): abstracts/ ed.: O. A. Maksimova, R. D. Ivantsov. - Krasnoyarsk: KIP RAS SB, 2016. - Ст.O2.7. - P.140. - ISBN 978-5-904603-06-9 (Шифр -478014040)
Примечания : References: 4. - The work was supported by Russian Foundation for Basic Research Grant No.16-38-00400
Ключевые слова (''Своб.индексиров.''): peak effect--paramagnetic magnetization--bulk superconductors--critical current--irreversibility field
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Poperechny I. S., Krasikov A. A., Shaikhutdinov K. A., Dubrovskiy A. A., Popkov S. I., Balaev A. D., Yakushkin S. S., Bukhtiyarova G. A., Martyanov O. N., Raikher, Yu. L.
Заглавие : Dynamic magnetization of ε-Fe2O3 in pulse field: Evidence of surface effect
Место публикации : J. Appl. Phys.: American Institute of Physics, 2015. - Vol. 117, Is. 6. - Ст.063908. - ISSN 0021, DOI 10.1063/1.4907586. - ISSN 10897550(eISSN)
Примечания : Cited References:30. - The work was supported by RFBR Grant Nos. 14-02-96002 and 12-02-00897, and project MIG S26/617 from the Ministry of Education and Science of Perm Region.
Предметные рубрики: FERROMAGNETIC-RESONANCE
COERCIVE FIELD
NANOPARTICLES
ANISOTROPY
Аннотация: The magnetization dynamics of ε-Fe2O3 nanoparticles with an average size of about 9 nm is investigated. From comparison of the hysteresis loops obtained in quasi-static conditions and under pulse fields with amplitudes up to 200 kOe and pulse lengths 8–32 ms, it follows that the effective coercivity increases considerably with the variation rate of the imposed magnetic field. A theoretical explanation of this behavior is proposed. The model takes into account the superparamagnetic effects as well as the fact that magnetic anisotropy of the nanoparticles, along with the bulk term, includes a surface contribution. The latter, being of minor importance for the observed magnetic behavior of 25–100 nm particles, becomes essential when the particle size is below 10 nm. From the experimental data, a reference value of the surface anisotropy of nanodisperse ε-Fe2O3 is established, and evidence is presented to the effect that below 300 K this contribution does not significantly depend on temperature.
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Poperechny I. S., Krasikov A. A., Semenov S. V., Popkov S. I., Knyazev Yu. V., Kirillov V. L., Yakushkin S. S., Martyanov O. N., Raikher Y. L.
Заглавие : Dynamic remagnetisation of CoFe2O4 nanoparticles: thermal fluctuational thawing of anisotropy
Коллективы : [AAAA-A17-117103050081-1]; [AAAAA20-120020690030-5]
Место публикации : J. Phys. D. - 2021. - Vol. 54, Is. 27. - Ст.275003. - ISSN 0022-3727, DOI 10.1088/1361-6463/abf371. - ISSN 1361-6463(eISSN)
Примечания : 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)
Предметные рубрики: COBALT-FERRITE NANOPARTICLES
MAGNETIC-PROPERTIES
SIZE
COERCIVITY
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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10.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Balaev D. A., Stolyar S. V., Krasikov A. A., Bayukov O. A., Yaroslavtsev R. N., Velikanov D. A., Iskhakov R. S., Knyazev Yu. V.
Заглавие : Effect of the interparticle interactions on superparamagnetic relaxation
Коллективы : Российская академия наук, Физико-технический институт им. Е.К. Завойского ФИЦ Казанского научного центра РАН, Казанский (Приволжский) федеральный университет, Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : VIII Euro-Asian symposium "Trends in magnetism" (EASTMAG-2022): Book of abstracts/ program com. S. G. Ovchinnikov [et al.]. - 2022. - Vol. 1, Sect.: Magnetotransport, magnetooptics and magnetophotonics. - Ст.D.O11. - P.437-438. - ISBN 978-5-94469-051-7
Примечания : Cited References: 3. - This study was supported by the Russian Science Foundation, Project No. 21-72-00025 (https://rscf.ru/project/21-72-00025/)
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gokhfeld D. M., Semenov S. V., Balaev D. A., Yakimov I. S., Dubrovskiy A. A., Terentyev K. Yu., Freydman A. L., Krasikov A. A., Petrov M. I.
Заглавие : Establishing of peak effect in YBCO by Nd substitution
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН , Russian Foundation for Basic Research [16-38-00400]
Место публикации : J. Magn. Magn. Mater.: Elsevier Science, 2017. - Vol. 440. - P.127-128. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2016.12.089. - ISSN 1873-4766(eISSN)
Примечания : Cited References:10. - The work was supported by Russian Foundation for Basic Research Grant No. 16-38-00400.
Предметные рубрики: SUPERCONDUCTORS
Ключевые слова (''Своб.индексиров.''): peak effect--magnetization--bulk superconductors--critical current--ybco--nd3+
Аннотация: Y0.75Nd0.25Ba2Cu3O7−d superconductor has the peak effect with pronounced fishtail feature on magnetization hysteresis. The magnetic field of the peak effect maximum is in ~4 times higher than one of NdBa2Cu3O7−d. The magnetization hysteresis is tilted anticlockwise due to paramagnetic Nd3+ ions occurred on the surface of grains and in the vortex cores.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Dubrovskiy A. A., Popkov S. I., Stolyar S. V., Iskhakov R. S., Ladygina V. P., Yaroslavtsev R. N.
Заглавие : Exchange bias in nano-ferrihydrite
Место публикации : J. Appl. Phys.: American Institute of Physics, 2016. - Vol. 120, Is. 18. - Ст.183903. - ISSN 00218979, DOI 10.1063/1.4967912
Примечания : Cited References: 43. - The authors are grateful to M. Volochaev for measurements and O. A. Bayukov for Mössbauer study.This work was supported in part by the Ministry of Education and Science of the Russian Federation.
Ключевые слова (''Своб.индексиров.''): anisotropy--cooling systems--hysteresis--magnetic fields--magnetic materials--magnetism--nanomagnetics--nanoparticles--particle size--characteristic value--exchange bias--exchange bias effects--external magnetic field--field cooling--high anisotropy--minor hysteresis loop--superparamagnetic blocking--hysteresis loops
Аннотация: We report the results of investigations of the effect of cooling in an external magnetic field starting from the temperature over superparamagnetic blocking temperature TB on the shift of magnetic hysteresis loops in systems of ferrihydrite nanoparticles from ∼2.5 to ∼5 nm in size with different TB values. In virtue of high anisotropy fields of ferrihydrite nanoparticles and open hysteresis loops in the range of experimentally attainable magnetic fields, the shape of hysteresis loops of such objects in the field-cooling mode is influenced by the minor hysteresis loop effect. A technique is proposed for distinguishing the exchange bias effect among the effects related to the minor hysteresis loops caused by high anisotropy fields of ferrihydrite particles. The exchange bias in ferrihydrite is stably observed for particles not less than 3 nm in size or with TB over 40 K, and its characteristic value increases with the particle size. © 2016 Author(s).
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Balaev A. D., Stolyar S. V., Ladygina V. P., Iskhakov R. S.
Заглавие : Features of relaxation of the remanent magnetization of antiferromagnetic nanoparticles by the example of ferrihydrite
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 7. - P.1172-1178. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783420070033
Примечания : Cited References: 53
Аннотация: The relaxation of the remanent magnetization of antiferromagnetically ordered ferrihydrite nanoparticles at the exchange bias effect implemented in these systems has been investigated. The magnetization relaxation depends logarithmically on time, which is typical of the thermally activated hoppings of particle magnetic moments through the potential barriers caused by the magnetic anisotropy. The barrier energy obtained by processing of the remanent magnetization relaxation data under the field cooling conditions significantly exceeds the barrier energy under standard (zero field cooling) conditions. The observed difference points out the possibility of using the remanent magnetization relaxation to analyze the mechanisms responsible for the exchange bias effect in antiferromagnetic nanoparticles and measure the parameters of the exchange coupling of magnetic subsystems in such objects.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popkov S. I., Krasikov A. A., Semenov S. V., Dubrovskii A. A., Yakushkin S. S., Kirillov V. L., Mart'yanov O. N., Balaev D. A.
Заглавие : Features of the pulsed magnetization switching in a high-coercivity material based on ε-Fe2O3 nanoparticles
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk Krai; Krasnoyarsk Territorial Foundation [18-42-240012]
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 3. - P.445-453. - ISSN 1063-7834, DOI 10.1134/S1063783420030166. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 44. - The study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Krai, and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project no. 18-42-240012 "Magnetization Switching of Magnetic Nanoparticles in Strong Pulsed Magnetic Fields: New Approach to Studying the Dynamic Effects Related to the Magnetization of Magnetic Nanoparticles."
Предметные рубрики: HIGH-TEMPERATURE
WAVE ABSORBER
OXIDE
FIELD
TRANSITION
RESONANCE
Аннотация: The magnetic structure of the ε-Fe2O3 iron oxide polymorphic modification is collinear ferrimagnetic in the range from room temperature to ~150 K. As the temperature decreases, ε-Fe2O3 undergoes a magnetic transition accompanied by a significant decrease in the coercivity Hc and, in the low-temperature range, the compound has a complex incommensurate magnetic structure. We experimentally investigated the dynamic magnetization switching of the ε-Fe2O3 nanoparticles with an average size of 8 nm in the temperature range of 80–300 K, which covers different types of the magnetic structure of this iron oxide. A bulk material consisting of xerogel SiO2 with the ε-Fe2O3 nanoparticles embedded in its pores was examined. The magnetic hysteresis loops under dynamic magnetization switching were measured using pulsed magnetic fields Hmax of up to 130 kOe by discharging a capacitor bank through a solenoid. The coercivity Нс upon the dynamic magnetization switching noticeably exceeds the Нс value under the quasi-static conditions. This is caused by the superparamagnetic relaxation of magnetic moments of particles upon the pulsed magnetization switching. In the range from room temperature to ~ 150 K, the external field variation rate dH/dt is the main parameter that determines the behavior of the coercivity under the dynamic magnetization switching. It is the behavior that is expected for a system of single-domain ferro- and ferrimagnetic particles. Under external conditions (at a temperature of 80 K) when the ε-Fe2O3 magnetic structure is incommensurate, the coercivity during the pulsed magnetization switching depends already on the parameter dH/dt and is determined, to a great extent, by the maximum applied field Hmax. Such a behavior atypical of systems of ferrimagnetic particles is caused already by the dynamic spin processes inside the ε-Fe2O3 particles during fast magnetization switching.
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15.

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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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popkov S. I., Krasikov A. A., Velikanov D. A., Kirillov V. L., Martyanov O. N., Balaev D. A.
Заглавие : Formation of the magnetic subsystems in antiferromagnetic NiO nanoparticles using the data of magnetic measurements in fields up to 250 kOe
Место публикации : J. Magn. Magn. Mater. - 2019. - Vol. 483. - P.21-26. - ISSN 03048853 (ISSN) , DOI 10.1016/j.jmmm.2019.03.004
Примечания : Cited References: 76. - We are grateful S.V. Semenov and A.A. Dubrovskiy for their help, S.V. Komogortsev and A.D. Balaev for fruitful discussions, and M.N. Volochaev for the TEM measurements. The TEM investigations were carried out on the equipment of the Center of Collective Use of the Federal Research Center “Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences”.The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science, to the research project: «Magnetic reversal of magnetic nanoparticles in strong pulsed magnetic fields - a new approach to the study of dynamic effects associated with the magnetization of magnetic nanoparticles» (project no. 18-42-240012).
Ключевые слова (''Своб.индексиров.''): antiferromagnetic nanoparticle--external magnetic field--low temperature regions--magnetic subsystems--magnetically actives--magnetization curves--paramagnetic subsystems--pulsed magnetic fields--magnetic bubbles
Аннотация: It is well-known that the fraction of surface atoms and the number of defects in an antiferromagnetic particle increase with a decrease in the particle size to tens of nanometers, which qualitatively changes the properties of the particle. Specifically, in antiferromagnetic nanoparticles, spins in the ferromagnetically ordered planes can partially decompensate; as a result, an antiferromagnetic particle acquires a magnetic moment. As a rule, uncompensated chemical bonds of the surface atoms significantly weaken the exchange coupling with the antiferromagnetic particle core, which can lead to the formation of an additional magnetic subsystem paramagnetic at high temperatures and spin-glass-like in the low-temperature region. The existence of several magnetic subsystems makes it difficult to interpret the magnetic properties of antiferromagnetic nanoparticles. It is shown by the example of NiO nanoparticles with an average size of 8 nm that the correct determination of the contributions of the magnetic subsystems forming in antiferromagnetic nanoparticles requires magnetic measurements in much stronger external magnetic fields than those commonly used in standard experiments (up to 60–90 kOe). An analysis of the magnetization curves obtained in pulsed magnetic fields up to 250 kOe allows one to establish the contributions of the uncompensated particle magnetic moment μun, paramagnetic subsystem, and antiferromagnetic particle core. The μun value obtained for the investigated NiO particles is consistent with the Néel model, in which μun ∼ N1/2 (N is the number of magnetically active atoms in a particle), and thereby points out the existence of defects on the surface and in the bulk of a particle. It is demonstrated that the anomalous behavior of the high-field susceptibility dM/dH of antiferromagnetic NiO nanoparticles, which was observed by many authors, is caused by the existence of a paramagnetic subsystem, rather than by the superantiferromagnetism effect.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popkov S. I., Krasikov A. A., Semenov S. V., Dubrovskii A. A., Yakushkin S. S., Kirillov V. L., Mart'yanov O. N., Balaev D. A.
Заглавие : General regularities and differences in the behavior of the dynamic magnetization switching of ferrimagnetic (CoFe2O4) and antiferromagnetic (NiO) nanoparticles
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk region; Krasnoyarsk Regional Foundation for Science [18-42-240012]
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 9. - P.1518-1524. - ISSN 1063-7834, DOI 10.1134/S1063783420090255. - ISSN 1090-6460(eISSN)
Примечания : 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"
Предметные рубрики: PARTICLE-SIZE
EXCHANGE-BIAS
TEMPERATURE
STATE
COERCIVITY
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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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pankrats A. I., Balaev A. D., Skorobogatov S. A., Krasikov A. A., Kolkov M. I., Zharkov S. M., Zeer G. M., Pavlovskii M. S., Balaev D. A.
Заглавие : Inclined magnetic structures and magnetic phase diagrams for the Pb2Fe2−xMnxGe2O9 (x = 0.16) single crystal
Место публикации : J. Magn. Magn. Mater. - 2022. - Vol. 563. - Ст.170021. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2022.170021
Примечания : Cited References: 24. - 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. 20-42-2 40006 “Synthesis and Study of Pb 2+ and Bi 3+ -Containing Oxide Single Crystals with Partial Substitution in One of the Subsystems: Magnetic Structures and Magnetodielectric Effect”. The SEM and EDS studies were carried out at the Joint Scientific Center of the Siberian Federal University within the state assignment (#FSRZ-2020-0011) of the Ministry of Science and Higher Education of the Russian Federation
Аннотация: Single crystals of the Pb2Fe2?xMnxGe2O9 (x = 0.16) antiferromagnet have been grown. Using the specific heat measurements, a Neel temperature of TN = (42.0 ± 0.5) K for the synthesized crystals has been found. It has been shown using the magnetic measurements that, due to the competition between the magnetoanisotropic contributions of the iron and manganese subsystems in the crystals, near a temperature of Tc = 22 K, a spontaneous spin-reorientation transition occurs, the temperature of which in an applied magnetic field changes with the field value and orientation relative to the rhombic axes of the crystal. Based on the analysis of the temperature and field dependences of the magnetization obtained at different orientations of the magnetic field, it has been established that, below Tc, an inclined magnetic structure is formed in the crystal. The antiferromagnetic vector of the inclined structure rotates smoothly in the rhombic bc plane with increasing temperature from a direction close to the b axis at T = 4.2 K and tends to the rhombic c axis at T = Tc. The rotation of the antiferromagnetic vector occurs also at fixed temperatures T < Tc with increasing magnetic field. In the temperature range of Tc < T < TN, the antiferromagnetic vector is oriented along the rhombic c axis. Magnetic phase diagrams of states have been built for different magnetic field orientations relative to the rhombic axes of the crystal. The richest phase diagram is shown to correspond to the orientation H||c and contains, along with the above-listed states, one more inclined phase, in which the antiferromagnetic vector rotates toward the rhombic a axis direction with a change in temperature or magnetic field.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krasikov A. A., Knyazev Yu. V., Balaev D. A., Velikanov D. A., Stolyar S. V., Mikhlin Yu. L., Yaroslavtsev R. N., Iskhakov R. S.
Заглавие : Interparticle magnetic interactions and magnetic field dependence of superparamagnetic blocking temperature in ferrihydrite nanoparticle powder systems
Место публикации : Phys. B: Condens. Matter. - 2023. - Vol. 660. - Ст.414901. - ISSN 09214526 (ISSN), DOI 10.1016/j.physb.2023.414901. - ISSN 18732135 (eISSN)
Примечания : Cited References: 66. - This study was supported by his work was supported by the Russian Science Foundation, project no. 22-72-00134
Аннотация: In this study, nanoparticles of initial synthetic ferrihydrite have been coated with arabinogalactan. The synthesized series of samples with different degrees of coverage of particles has been characterized by X-ray photoelectron spectroscopy, Mossbauer spectroscopy, transmission electron microscopy and magnetometry. The superparamagnetic blocking temperature decreases monotonically with an increase in the degree of coverage of ferrihydrite particles, which is unambiguously related to the different role of the interparticle magnetic interactions in the investigated powder systems. Analysis of the field dependence of the blocking temperature within the random anisotropy model has shown that an increase in the degree of coverage of ferrihydrite particles leads to a decrease in the size of a cluster in which the behaviors of the nanoparticle magnetic moments are correlated. The results obtained have shown the possibility of effective control of the strength of magnetic interparticle interactions in powder ferrihydrite systems by coating nanoparticles with arabinogalactan.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Balaev D. A., Stolyar S. V., Krasikov A. A., Bayukov O. A., Volochaev M. N., Yaroslavtsev R. N., Ladygina V. P., Velikanov D. A., Iskhakov R. S.
Заглавие : Interparticle magnetic interactions in synthetic ferrihydrite: Mossbauer spectroscopy and magnetometry study of the dynamic and static manifestations
Место публикации : J. Alloys Compd. - 2022. - Vol. 889. - Ст.161623. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2021.161623
Примечания : 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”
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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