ε-Fe2O3 nanoparticles embedded in silica xerogel – Magnetic metamaterial

Panjan

Journal of Electrical Engineering

et al. 2019

Using the sol-gel method we synthesized hematite (α − Fe2O3) nanoparticles in a silica matrix with 60 wt % of hematite. X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra of the sample demonstrate the formation of the α − Fe2O3 phase and amorphous silica. A transmission electron microscopy (TEM) measurements show that the sample consists of two particle size distributions of the hematite nanoparticles with average sizes around 10 nm and 20 nm, respectively. Magnetic properties of hematite nanoparticles were measured using a superconducting quantum interference device (SQUID). Investigation of the magnetic properties of hematite nanoparticles showed a divergence between field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves and two maxima. The ZFC magnetization curves displayed a maximum at around TB = 50 K (blocking temperature) and at TM = 83 K (the Morin transition). The hysteresis loop measured at 5 K was symmetric around the origin, with the values of coercivity, remanent and mass saturation magnetization HC10K ≈ 646 A/cm, (810 Oe), Mr10K = 1.34 emu/g and MS10K = 6.1 emu/g respectively. The absence of both coercivity (HC300K = 0) and remanent magnetization (Mr300K = 0) in M(H) curve at 300 K reveals super-paramagnetic behavior, which is desirable for application in biomedicine. The bimodal particle size distributions were used to describe observed magnetic properties of hematite nanoparticles. The size distribution directly influences the magnetic properties of the sample.

Section: Introductionmentioning

confidence: 99%

Magnetic properties of hematite (α − Fe₂O₃) nanoparticles synthesized by sol-gel synthesis method: The influence of particle size and particle size distribution

Panjan

Journal of Electrical Engineering

et al. 2019

“…Магнитные свойства наноструктурированных систем определяются не только молекулярной формулой компонентов, но и наличием неоднородностей на наномасштабе [5]. Высокая чувствительность магнитных взаимодействий к структурным неоднородностям является ключевым фактором, который открывает широкие возможности для создания систем с уникальными свойствами [6][7][8], что и определяет повышенный интерес исследователей к данной области.…”

Section: Introductionunclassified

Синтез и магнитные свойства наночастиц Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=-/CoFe-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=- со структурой ядро/оболочка

Balaev¹,

Semenov²,

Dubrovskiĭ³

et al. 2020

Физика Твердого Тела

Fe3O4 / CoFe2O4 nanoparticles with a core-shell structure with an average size of 5 nm were obtained by co-precipitation from solutions of iron and cobalt chlorides. An analysis of the magnetic properties of the resulting system and their comparison with the data for single-phase Fe3O4 (4 nm) and CoFe2O4 (6 nm) nanoparticles led to the conclusion that there is a noticeable interaction between the soft magnetic (Fe3O4) and magnetically hard (CoFe2O4) phases that form the core and the shell of hybrid particles, correspondingly.

“…С целью установления картины температурной эволюции динамической коэрцитивной силы, а также выявления причин указанного расхождения модели и эксперимента при T = 77 K в данной работе проведены исследования импульсного перемагничивания материала на основе наночастиц ε-Fe 2 O 3 (средний размер ∼ 8 nm). Диапазон, в котором проведены измерения, составляет 80−300 K, что охватывает как магнитожесткую фазу (температурный диапазон ее существования 150−500 K), так и сложную (в точности неустановленную к настоящему времени) несоразмерную магнитную структуру при 80 K, формирующуюся после магнитного перехода, происходящего в температурном интервале 80−150 K. [27,28].…”

Section: Introductionunclassified

Особенности импульсного перемагничивания высококоэрцитивного материала на основе наночастиц ε-Fe-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

Попков¹,

Красиков²,

Семенов³

et al. 2020

Физика Твердого Тела

The magnetic structure of the polymorphic modification of iron oxide ε-Fe2O3 is collinear ferrimagnetic in the range from room temperature to ~ 150 K. Further, with decreasing a temperature in ε-Fe2O3, a magnetic transition occurs, accompanied by a significant decrease in the coercive force HC, and in the low temperature range ε-Fe2O3 is characterized by a complex incommensurate magnetic structure. In this work, we experimentally investigated the processes of dynamic magnetization reversal of ε-Fe2O3 nanoparticles of an average size of 8 nm in the temperature range of 80–300 K, comprising various types of magnetic structure of this iron oxide. A bulk material was studied - xerogel SiO2 with ε Fe2O3 nanoparticles embedded in pores. To measure the magnetic hysteresis loops under dynamic magnetization reversal, a pulsed magnetic field technique of Hmax up to 130 kOe was used, using the method of discharging a capacitor bank through a solenoid. The coercive force of HC during dynamic magnetization reversal noticeably exceeds HC for quasi-static conditions. This is caused by processes of superparamagnetic relaxation of the magnetic moments of particles during pulsed magnetization reversal. In the range from room temperature to ~ 150 K, the rate of change of the external field dH / dt is the main parameter determining the behavior of the coercive force under the conditions of dynamic magnetization reversal. This behavior is expected for a system of single-domain ferro- and ferrimagnetic particles. Under external conditions (at a temperature of 80 K), when the magnetic structure of ε Fe2O3 is incommensurate, the coercive force during pulsed magnetization reversal already depends on the parameter dH / dt, and is largely determined by the maximum applied field Hmax. Such a behavior, atypical for systems of ferrimagnetic particles, is already caused by dynamic spin processes inside ε-Fe2O3 particles during fast magnetization reversal.