Films of metal-insulator nanogranular composites M_xD_100-x with different compositions and atomic percentage of metal and dielectric phases (M = Fe, Co, Ni, CoFeB; D = Al_2O_3, SiO_2, ZrO_2; x ≈ 15-60 at. are investigated by electron magnetic resonance in a wide range of frequencies (f = 7-37 GHz) and temperatures (T = 4.2-360 K). At concentrations of the metallic ferromagnetic phase below the percolation threshold, the experimental spectra, besides the conventional ferromagnetic resonance signal, demonstrate an additional absorption peak characterized by a double effective g-factor g ≈ 4. The appearance of such a peak in the resonance spectra and its unusual properties are explained in the framework of the quantum mechanical "giant spin" model by the excitation of "forbidden" ("double quantum") transitions in magnetic nanogranules with a change of the spin projection Δ m = ±2.

The possibility of electrochemical formation of Al–Ni composite coatings from an aluminum suspension in an electrolyte based on a deep eutectic solvent has been studied. The composition of the electrolyte was proposed, and the influence of the aluminum content on the composition, structure, and morphology of the coating was studied.

Abstract—The work is devoted to the study of the properties and selection of the optimal method for applying an intermediate coating on steel, which serves as an adhesive support layer for extremely hard CVD coatings. In this work, a study of the structure and properties of multilayer coatings of the Ni–P and W–C systems was carried out. The morphology, phase and elemental composition of the layers obtained have been studied by scanning electron microscopy, X-ray diffractometry and X-ray photoelectron spectroscopy. It is shown that nickel coatings consist mainly of a metallic phase, despite the high phosphorus content in the Ni-P layers. Mechanical tests of the coatings showed that the support layer obtained by the method of electroless plating tends to increase in hardness, and tests for adhesion strength showed some advantage of electroless nickel plating over electroplating, providing a higher resistance to destructive effects during testing.

Films of metal-insulator nanogranular composites M x D 100 – x with different composition and percentage of metal and dielectric phases (M = Fe, Co, CoFeB; D = Al 2 O 3 , SiO 2 , LiNbO 3 ; x ≈ 15–70 at %) are investigated by magnetic resonance in a wide range of frequencies ( f = 7–37 GHz) and temperatures ( T = 4.2–360 K). In addition to the usual ferromagnetic resonance signal from an array of nanogranules, the experimental spectra contain an additional absorption peak, which we associate with the electron paramagnetic resonance (EPR) of Fe and Co ions dispersed in the insulating space between the granules. In contrast to the traditional EPR of Fe and Co ions in weakly doped non-magnetic matrices, the observed peak demonstrates a number of unusual properties, which we explain by the presence of magnetic interactions between ions and granules.

The features of the interface of the W–C system obtained by chemical-vapor deposition and Ni‒P–W layers of various compositions obtained by chemical-catalytic metallization are studied. Ni–P–W layers are used as support layers for coatings of the W–C system to improve the adhesive strength of the applied coatings to steels and resistance to loads directed along the normal to the surface. The methods of scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are used to study the morphology, and phase and elemental composition of the obtained layers, as well as phase transformations occurring in the layers during heat treatment. Mechanical tests show that Ni–P layers with a low phosphorus content, in terms of their characteristics, demonstrate the best support properties.

Films of metal-insulator nanogranular composites MxD100 – x with different composition and percentage of metal and dielectric phases (M = Fe, Co, CoFeB; D = Al2O3, SiO2, LiNbO3; x ≈ 15–70 at %) are investigated by magnetic resonance in a wide range of frequencies (f = 7–37 GHz) and temperatures (T = 4.2–360 K). In addition to the usual ferromagnetic resonance signal from an array of nanogranules, the experimental spectra contain an additional absorption peak, which we associate with the electron paramagnetic resonance (EPR) of Fe and Co ions dispersed in the insulating space between the granules. In contrast to the traditional EPR of Fe and Co ions in weakly doped non-magnetic matrices, the observed peak demonstrates a number of unusual properties, which we explain by the presence of magnetic interactions between ions and granules.

This article is devoted to an overview of approaches to improving the characteristics of electrosurgical instruments. Currently, in minimally invasive surgery, the main material of an electrosurgical instrument is usually stainless steel. However, during operation, tissue sticking and carbonization occur, as well as corrosion of the instrument, which leads to a decrease in efficiency and adverse events. In this regard, it is very promising to develop new physicochemical approaches to improve the characteristics of electrosurgical instruments in order to avoid disadvantages noted above. On the one hand, it is proposed to replace stainless steel with other electrically conductive materials (gold, tungsten, zirconium dioxide, etc.). On the other hand, options for developing functional coatings of stainless steel (metallic, polymeric and composite) are considered. Among the "classical" approaches, one can distinguish coatings with gold, as well as nitrides and oxides of refractory metals (Cr, Zr, Ti), which are characterized by higher thermal conductivity and a pronounced anti-sticking effect. Very promising is the use of coatings based on diamond-like carbon, which have a higher contact angle compared to stainless steel (97.25 +/- 1.87 degrees versus 75.47 +/- 2.55 degrees) with a higher microhardness of the coating (2250 Hv versus 500 Hv). Particular attention is drawn to superhydrophobic coatings, for example, a coating based on hexamethyldisilazane with Sid e nanoparticles, the contact angle of which is two times higher than stainless steel (153.4 +/- 2.6 degrees versus 73.1 +/- 0.6 degrees). An alternative to coatings is the formation of microchannels and nanoroughness on the surface of electrosurgical instruments in order to reduce tissue adhesion and the risk of carbonization. Implementation of the principles of biomimicry, i.e. imitation of the structures of wildlife, has led to research in the field of creating analogues of microstructures (pangolin scales, shark skin), as well as liquid-infused surfaces, imitating the properties of the leaves of the carnivorous Nepenthes pitcher plant, which, due to the lubricant layer on their surface, have lower adhesive properties compared to unmodified material. Thus, the problem of modifying the surface of electrosurgical instruments has already been approached from several angles, and it can be stated with a sufficient degree of confidence that the number of studies in this direction will only increase.

Magnetic characteristics of iron borate, FeBO3, film on diamagnetic gallium borate substrate were determined from electron magnetic resonance studies in the microwave frequency range of 15–36 GHz and the temperature range of 4 K to room temperature. The temperature dependence of the Dzyaloshinskii–Moriya field in the film is in accordance with that previously determined for FeBO3 single crystals. In contrast, the isotropic energy gap in the film is several times larger than in the single crystal. This discrepancy has been related to deformations caused by the mismatch between the lattice parameters of the film and the substrate.

Films of metal–insulator nanogranular (CoFeB)x(LiNbO3)100 – x and (CoFeB)x(Al2O3)100 – x composites with different content x of a ferromagnetic metallic phase have been investigated by the magnetic resonance method in a wide temperature range (4.2–360 K). The systems under study are characterized by a high concentration of paramagnetic Fe and Co ions, which are dispersed in the insulating medium between ferromagnetic CoFeB granules. The experimental spectra of these systems show a peak of ferromagnetic resonance associated with the ferromagnetic granule array and an additional less intense absorption peak associated with the electron paramagnetic resonance of Fe3+ ions in the insulating matrix. It has been found that the position and intensity of this peak depend on the composition of the system and temperature. The observed behavior is explained by existence of exchange interaction between magnetic ions and ferromagnetic granules.

The room-temperature magnetic resonance spectra of metal–insulator (CoFeB)x(LiNbO3)100 – x and (CoFeB)x(Al2O3)100 – x nanogranular composite films with various ferromagnetic metallic phase contents x near the percolation threshold are investigated. The systems under study are characterized by a high concentration of paramagnetic ions dispersed in an insulator matrix between ferromagnetic granules. In addition to a usual ferromagnetic resonance signal, these films are found to exhibit an additional absorption peak in weak fields. In contrast to the usual ferromagnetic resonance excited by a transverse high-frequency magnetic field, the additional peak demonstrates a weak dependence of its amplitude on the resonance excitation geometry. The position of this peak depends on the composition of the system, the resonance excitation frequency (f = 7–38 GHz), and the magnetic field orientation with respect to the film plane. This behavior is associated with the paramagnetic resonance of Fe3+ ions, which are present in the insulator matrix and interact with ferromagnetic granules.

Thin films of MnxSi1 – x (x ≈ 0.5) alloy were synthesized by pulsed laser deposition in a droplet-free mode on sapphire substrates with different crystallographic cut-off plane orientations (c-Al2O3 and r-Al2O3) at various laser energy densities E at the polycrystalline target MnSi. X-ray structure properties, as well as static and resonance magnetic characteristics of the films depending on the value of E and substrate orientation were investigated. The presence of a ferromagnetic phase with an unusually high Curie temperature TC ~ 300 K which is untypical of MnSi single crystals (TC ~ 30 K) was revealed in films deposited using high laser energy densities E > 6 J/cm2 at the target. The magnetic moment of the films on c-Al2O3 substrates is somewhat larger than in the case of r-Al2O3 substrates. Moreover, the films deposited on c-Al2O3 substrates show significantly higher values of the effective magnetic anisotropy field 4πMeff, measured by ferromagnetic resonance. Obtained data show that the structure of the substrate has a remarkable influence on the formation process and magnetic properties of the high-temperature ferromagnetic phase in the MnxSi1 – x films.

The magnetocaloric effect in nanosystems based on exchange-coupled ferromagnets with different Curie temperatures is calculated within the mean-field theory. Good agreement between the results of the mean-field theory and the Landau theory, valid near the critical phase transition temperature, is demonstrated for a flat-layered Fe/Gd/Fe structure. We show that a high magnetic cooling efficiency in this system is attainable in principle and prove the validity of the Maxwell relation, enabling an experimental verification of the predictions made. The theory developed for flat-layered structures is generalized to a granular medium.

Thin films of MnxSi1-x (x ≈ 0.5) alloy were synthesized by pulsed laser deposition in a droplet-free mode on sapphire substrates with different crystallographic orientations of the cut plane (c-Al2O3 and r-Al2O3) at various laser energy densities E at the polycrystalline MnSi target. The X-ray structural, as well as static and resonance magnetic properties of the films were studied depending on E and the orientation of the substrate. The films deposited at high E > 6 J/cm2 are found to demonstrate the presence of a ferromagnetic phase with anomalously high Curie temperature TC ~ 300 K which is not typical of MnSi single crystals (TC ≈ 30 K). In the case of the c-Al2O3 sub-strates, the magnetic moment of the films turns out to be somewhat higher than in the case of the r-Al2O3 substrates. Moreover, the films deposited on the c-Al2O3 substrates exhibit noticeably higher values of the effective surface anisotropy field 4πMeff measured by ferromagnetic resonance. The data obtained indicate a significant effect of the substrate structure on the formation and magnetic properties of the high-temperature ferromagnetic phase in the MnxSi1-x films.

Магнитокалорический эффект (МКЭ) заключается в изменении температуры образца при приложении внешнего магнитного поля. Классическим примером МКЭ является охлаждение парамагнитных солей до сверхнизких (10−2−10−3 K) температур при их адиабатическом размагничивании [1]. В последние годы интерес к МКЭ связан с возможностью создания “магнитных холодильников” на основе сплавов гадолиния, работающих при комнатной температуре [2, 3]. Эффективность адиабатического магнитного охлаждения характеризуется отношением dT/dH изменения температуры образца к изменению магнитного поля. Достигнутые к настоящему времени значения эффективности охлаждения при адиабатическом размагничивании в однородном внешнем поле не превышают 10 град./Тл [4]. Целью данной работы является исследование магнитокалорического эффекта в магнитных многослойных структурах, для которых намагничивание (или размагничивание) определяется эффектом “близости”, связанным с обменным взаимодействием различных магнитных слоев. Мы покажем, что эффективность магнитного охлаждения в этих системах может достигать предельного значения в однородных системах, или даже превышать его [4]. Отметим, что изучение особенностей МКЭ в наноструктурах вызывает возрастающий интерес [5, 6]. Рассмотрим многослойную структуру F/f/F, где под F понимается “сильный” ферромагнетик, температура Кюри которого выше температуры образца (TF > T ), а под f – прослойка “слабого” ферромагнетика, для которого температура Кюри Tf < TF. Тем-

Thin films of MnxSi1-x (x ~ 0.5) were obtained by pulsed laser deposition in droplet-free mode on c- and r-Al2O3 substrates at different laser energy densities E at the target. Their structural, electrical, and magnetic properties were studied depending on the value of E and the orientation of the substrate. The films are X-ray amorphous on the substrates of both types at E < 6.8 J/cm2, and only at E ≅ 6.8 J/cm2 the reflections of ε-MnSi crystallites with B20-type of structure begin to appear in the MnxSi1-x films on c-Al2O3 and at E ≅ 7.4 J/cm2 - on r-Al2O3 substrates. The X-ray diffraction data of the samples indicate the presence in the films of the ε-MnSi nanocrystallites of an optimal size for the manifestation of high-temperature ferromagnetism; the concentration of nanocrystallites is controlled by the type of substrate and the energy density at the target. It is found that at E > 5.5 J/cm2 the high-temperature ferromagnetic phase shows in the films, and at E ≅ 4 - 5 J/cm2, the low-temperature ferromagnetic phase predominates and there is no influence of the sapphire substrate orientation. The highest Curie temperature TC reached was 330 K at E ≅ 7.4 J/cm2 for the MnxSi1-x films obtained on c- and r-Al2O3. The correlated behavior of the magnetization and the signal of diffuse X-ray radiation scattering confirms the existence of ε-MnSi nanocrystallites.

Metal-insulator nanocomposite (CoFeB)x(LiNbO3)1−x films are studied by the ferromagnetic resonance method in the temperature range of 4–320 K. In the low-temperature region, the maximum of the ferromagnetic resonance linewidth and a negative dynamic shift of the absorption peak, typical of the mechanism of slow ion relaxation on magnetic impurities, are found. The observed magnetic relaxation features can be caused by paramagnetic Co and Fe ions, which are dispersed in the dielectric LiNbO3 matrix and are exchange-coupled to ferromagnetic CoFeB granules. Experimental temperature dependences of the ferromagnetic resonance linewidth and shift are in good agreement with theoretical curves obtained within the proposed approach.