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Найдено документов в текущей БД: 3

    Magnetic structure and size-effects in the system of epsilon-Fe2O3/SiO2 nanoparticles
/ S. S. Yakushkin [et al.] // VI Euro-Asian Symposium "Trends in MAGnetism" (EASTMAG-2016) : abstracts / ed.: O. A. Maksimova, R. D. Ivantsov. - Krasnoyarsk : KIP RAS SB, 2016. - Ст. O9.5. - P. 383. - References: 6 . - ISBN 978-5-904603-06-9

Кл.слова (ненормированные):
ε-Fe2O3 nanoparticles -- superparamagnetic nanoparticles -- size effect -- FMR



Доп.точки доступа:
Yakushkin, S. S.; Якушкин С. С.; Balaev, D. A.; Балаев, Дмитрий Александрович; Shaikhutdinov, K. A.; Шайхутдинов, Кирилл Александрович; Dubrovsky, A. A.; Дубровский, Андрей Александрович; Bukhtiyarova, G. A.; Martyanov, O. N.; Euro-Asian Symposium "Trends in MAGnetism"(6 ; 2016 ; Aug. ; 15-19 ; Krasnoyarsk); "Trends in MAGnetism", Euro-Asian Symposium(6 ; 2016 ; Aug. ; 15-19 ; Krasnoyarsk); Институт физики им. Л.В. Киренского Сибирского отделения РАН

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    The Low-Temperature Magnetic State and Magnetic Ordering Temperature of ϵ-Fe2O3 Iron Oxide Nanoparticles
/ A. Dubrovskiy [et al.] // IEEE Magn. Lett. - 2019. - Vol. 10. - Ст. 6110103, DOI 10.1109/LMAG.2019.2956674. - Cited References: 22 . - ISSN 1949-307X
Аннотация: The ϵ-Fe2O3 iron oxide polymorph is a well-known magnetic material with a complex magnetic structure, which undergoes a series of magnetic transitions in different temperature ranges. However, the ϵ-Fe2O3 phase diagram is still unclear. We report on the magnetic properties of a sample consisting of ϵ-Fe2O3 nanoparticles with an average size of 8 nm embedded in a SiO2 xerogel matrix without an admixture of foreign phases. Along with the features typical of the well-known ϵ-Fe2O3 magnetic transition in the temperature range 80–150 K, the temperature dependence of magnetization M(T) of ϵ-Fe2O3 includes other low-temperature anomalies. In an external field of H = 70 kOe, there is a noticeable temperature hysteresis of magnetization at 50–90 K, and near T ≈ 50 K, the M(T) curves have a characteristic bending, which may be indicative of an additional magnetic transition. The ferromagnetic resonance spectra shows that, near 500 K, a magnetic phase transition occurs, which was previously thought to be a transition to the paramagnetic state. An analysis of the temperature dependence of the ferromagnetic resonance spectra shows that the magnetically ordered phase in ϵ-Fe2O3 exists up to about 800 K.

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Держатели документа:
Kirensky Institute of Physics SB RAS, 133887 Krasnoyarsk, Russian Federation
Boreskov Institute of Catalysis SB RAS, 104675 Novosibirsk, Russian Federation

Доп.точки доступа:
Dubrovskiy, A. A.; Дубровский, Андрей Александрович; Semenov, S. V.; Семёнов, Сергей Васильевич; Knyazev, Yu. V.; Князев, Юрий Владимирович; Popkov, S. I.; Попков, Сергей Иванович; Yakushkin, S.; Kirillov, V.; Martyanov, O.; Balaev, D. A.; Балаев, Дмитрий Александрович

    Features of the pulsed magnetization switching in a high-coercivity material based on ε-Fe2O3 nanoparticles
/ S. I. Popkov, A. A. Krasikov, S. V. Semenov [et al.] // Phys. Solid State. - 2020. - Vol. 62, Is. 3. - P. 445-453, DOI 10.1134/S1063783420030166. - 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." . - ISSN 1063-7834. - ISSN 1090-6460
РУБ Physics, Condensed Matter

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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Держатели документа:
Russian Acad Sci, Kirensky Inst Phys, Krasnoyarsk Sci Ctr, Siberian Branch, Krasnoyarsk 660036, Russia.
Russian Acad Sci, Boreskov Inst Catalysis, 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 Krai; Krasnoyarsk Territorial Foundation [18-42-240012]