A combination of X-ray diffraction, Mössbauer spectroscopy, and measurements of magnetic characteristics are used to study the crystal structure, morphology, and magnetic properties of nanocomposite powders based on transition metals Ni, Co, Cu, and Fe, synthesized in low-temperature underwater plasma for the first time. Results demonstrate the possibility of synthesizing nanocomposites with given contents of NiFe2O4, CoFe2O4, and Ni1 – xCuхFe2O4 ferrites, which ensure small ferromagnetic resonance linewidths, and ε-Fe2O3, which has high frequency resonance in the millimeter range of electromagnetic radiation.

Using atomic force microscopy methods, the surface structure of strip amorphous alloys—foils based on the composition Fe73(SiBNb)27, obtained by ultra-fast cooling by spraying the melt on a rapidly rotating copper drum was studied. The morphology of free and contact surfaces of foils was studied.

A mixed magnetite–maghemite solid solution and a bentonite–iron oxide composite material are synthesized via chemical coprecipitation. It is found that the bentonite–iron oxides composite is characterized by considerably weaker residual magnetization and stronger coercive force than Fe3O4/γ-Fe2O3 powder. X-ray diffraction and Mössbauer spectroscopy data show that bentonite influenced structural features of the magnetite–maghemite in the composite.

Magnetic force microscopy is used to investigate the effect magnetic pulse treatment has on the local magnetic properties of surfaces of ribbon amorphous Fe(Ni,Cu)(SiB) alloys obtained via ultrafast cooling of melts sprayed onto a rotating copper drum.

Results are presented from studying the effect magnetic pulse processing has on the local structure and magnetic properties of substituted ferrite BaFe12 – xZnxO19 (0.25 ≥ x ≥ 0) for microwave devices. The change in the magnetic properties of ferrites due to the action of weak magnetic field pulses testifies to the possibility of controlling the parameters of ferrites by magnetic fields and affecting the resonant characteristics of microwave devices based on them.

We explore the specific features of the surface state that determine the domain structure, magnetic properties and magnetic loss upon magnetization reversal of ribbon amorphous Fe(Ni,Cu)(SiB) alloys obtained by ultrafast cooling by melt sputtered onto a rotating drum. We use scanning electron microscopy, atomic-force microscopy, and magnetic-force microscopy and measurements of the magnetic characteristics before and after treatment by pulses of a weak magnetic field (10–100 kA/m) of low frequency (10–20 Hz). Both foil surfaces are studied. The surfaces of the samples adjacent to the copper drum had an inhomogeneous structure, typical of all rapidly hardened samples. The other sides of the foils are smoother, which make them look shiny. Atomic-force microscopy shows no changes in the surface structure of the foils after their magnetic-pulse processing. Changes are detected in the images of the shiny side of the samples, obtained by magnetic-force microscopy. No domain structure is observed in the samples before magnetic-pulse processing. After magnetic-pulse treatment, stripe domains with a width of 0.6–0.8 nm and closure domains with a width of 1.0–1.6 nm are found at structural defects, and a weak magnetic contrast as large and small domains with a shape close to triangular is detected in some areas of the surface. The magnetization-reversal loss is largely related to the loss caused by eddy currents and is affected by the domain width (about 1.5 nm), which depends only slightly on the modes of magnetic-pulse processing. The results can be used to refine the procedure for relieving stress arising during the manufacturing of amorphous ribbons.

Atomic force microscopy and magnetic force microscopy have been used to study the influence of weak magnetic field pulses on the local properties of ribbon amorphous Fe(Ni, Cu)(SiB) alloys about 100 µm thick, 10 mm wide, and 50 mm long, which were obtained by ultrafast cooling of the melt on a rotating copper drum. On the surface of the tape adjacent to the copper drum, there were practically no areas with low rough-ness, which did not allow subsequent studies of this side of the tape by magnetic force microscopy. This method was used to investigate another, free surface of the foil, which was not adjacent to the copper drum and did not have significant roughness. Prior to the impact of magnetic field pulses on the foil, no magnetic contrast was observed on the free side of the ribbon. After magnetic pulse processing, a magnetic contrast was registered on this side of the foil: stripe domains 0.6–0.8 μm wide became visible, and closing domains, became visible on structural defects, wedge-shaped Neel domains, from 1 µm to 1.6 µm wide. The results of the study allow us to say that the magnetization reversal losses are to a large extent associated with losses due to eddy currents and are associated with the domain width, which depends slightly on the modes of magnetic pulse processing. The obtained results of the research can be used to refine the method for relieving stresses arising in the process of manufacturing amorphous ribbons.

Results are presented from studying nanosized particles of NiFe2O4 and ɛ-Fe2O3, synthesized in low temperature underwater plasma. It is shown that nanocomposites with a fixed ratio of nickel ferrite (which ensures low values of the ferromagnetic resonance linewidth) and ɛ-Fe2O3 (which exhibits high-frequency resonance in the millimeter range of electromagnetic radiation) can be synthesized.

The properties of synthesized nanostructured materials are determined by the methods of their preparation. The combination of electric discharges with liquid is a new tool for the synthesis of pure structures but the conditions for obtaining structures play an important role as in the case of traditional synthesis methods. In this work, the electrical and emission characteristics of a low-temperature direct-current plasma in contact with water at currents of 0.25 and 0.80 A are studied. The values of the power (energy) of single discharges are calculated. It is established that this type of discharge burns in the pulsed mode. The value of the discharge current affects the frequency of occurrence of discharges and the energy of a single discharge. It is shown that low-temperature underwater plasma is an effective tool for the synthesis of nanocomposites based on metal oxides, the precursors of which are metal electrodes. The emission spectroscopy method is used to study the emission spectra of underwater plasma. The sputtering of electrodes during plasma combustion is established. X-ray phase analysis shows that the phase composition of the resulting products is determined by the strength of the plasma current. The formation of oxides and hydroxides of Ni and Cr with different valences of metal ions is found.

Атомно-силовая микроскопия аморфных электротехнических сплавов Fe(Ni, Cu)(SiB) Т.П.Каминская 1 , М.Н.Шипко 2 , М.А.Степович 3 , В.В.Попов 1 , А.И.Тихонов 2 1 Московский государственный университет им.М.В.Ломоносова г.Москва 2 Ивановский государственный энергетический университет им.В.И.Ленина, г.Иваново 3 Калужский государственный университет им.К.Э.Циолковского, г

A study is performed of the effect magnetic pulse treatment has on the electromagnetic properties and crystal structure of high-temperature multiferroics (scandium-substituted barium hexaferrites). It is shown that a pulsed magnetic field enhances the covalence of the chemical bonds between Fe3+ ions in fivefold coordination and non-centered octahedra as a result of the ordering of ions, cationic and anion vacancies, and additional displacement of Sc3+ and Fe3+ ions from the center of polyhedra.

An investigation is performed of synthesized halloysite/magnetite composite materials and their porous structure, surface morphology, and physicochemical properties. It is established that the halloysite/magnetite composite samples have values of the effective field of anisotropy and coercive force that are higher than those found for magnetite.

Halloysite is modified with magnetite nanoparticles by the chemical coprecipitation of iron salts. To characterize the surface and study the physical-chemical properties of the resulting composite and its components (halloysite and magnetite), we use dynamic light scattering, electron microscopy, the low-temperature adsorption–desorption of nitrogen, X-ray diffraction analysis, Mössbauer and IR (infrared) spectroscopy, and magnetic measurements. Energy-dispersive analysis data and X-ray diffraction patterns confirm the modification of halloysite by magnetite nanoparticles, changing the zeta potential and the adsorption capacity of the surface. IR spectral analysis of the studied composites reveal shifts in the characteristic bands of halloysite and magnetite during their formation. The halloysite/magnetite composite samples have a higher field strength of effective anisotropy and coercive force compared to magnetite.

Different structures of iron oxides are obtained via reagent-free synthesis under the low-temperature plasma of an electric discharge in contact with a liquid. Experimental results are explained using a geometric model built from data on layered structure of iron oxides. A mechanism is proposed for the transformation of an FeO lattice into an Fe3O4 or Fe2O3 polymorph.

Halloysite/magnetite composite was synthesized by chemical coprecipitation. To evaluate the crystal structure, texture, surface morphology, and magnetization of the composite, electron microscopy, low-temperature nitrogen adsorption–desorption, X-ray diffraction analysis, and magnetic measurements were used. Granulometric analysis of the obtained materials showed that larger particles appear when halloysite is modified with magnetite. It was revealed that the studied samples of halloysite and composite belong to mesoporous bodies. An increase in the size of magnetite crystallites was found in the structure of magnetized clay. It is shown that samples of magnetized halloysite are characterized by higher values of the coercive force and lower values of the specific saturation magnetization compared to those found for magnetite.

Polycrystalline spinel ferrites of composition Li0.33Fe2.29Zn0.21Mn0.17O4 have been synthesized by the ceramic method at sintering temperatures of 950, 1000, 1050, and 1100°С. The crystal structure of the resulting samples has been studied by X-ray powder diffraction, and the chemical composition of the ferrites has been refined by the secondary ion mass spectrometry. Magnetic characteristics of the samples have been measured on an MK-3E magnetic measuring device. Room-temperature Mössbauer spectra have been recorded on an Ms-1104 Em spectrometer. The cation distribution in the crystal lattice of the resulting ferrites has been established; crystal chemical formulas have been calculated for each sintering temperature. The Mössbauer spectra of all the obtained samples are modeled by five sextets, which is explained by the appearance of nonequivalent Fe3+ ions in octahedral and tetrahedral positions, differing in the composition of the second coordination sphere. Combinations of lithium, manganese, and zinc ions in the nearest cationic environment of octahedral iron ions have been determined on the basis of a model that takes into account the peculiarities of changes in the Mössbauer parameters with an increase in the sintering temperature of ferrites. It has been shown that Mössbauer spectroscopy in combination with X-ray powder diffraction and magnetometry provides efficient control of the phase composition, cation distribution, and magnetic properties in substituted ferrites.