Efficient heating of magnetic nanoparticles by means of the ferromagnetic resonance method is demonstrated with the use of isotropic superparamagnetic nickel ferrite powder as an example. The kinetic heating curves Delta T ( t ) were measured at frequency of f = 8.9 GHz. It is shown that the obtained Delta T values are fairly well described by theoretical expressions for the absorption of microwave energy in an isotropic superparamagnet. This imparts some basic quantification to the idea of magnetic hyperthermia that operates in the ultra-high frequency range.

The structure, magnetic properties and ferromagnetic resonance curves of cobalt ferrite particles synthesized by chemical coprecipitation technique have been studied. The possibility of resonant heating of powder in a magnetic anisotropy field of particles is shown, which can find application in medicine for magnetic hyperthermia.

Results are presented from investigating the ferromagnetic resonance spectra of arrays of Co‒Ni and Co‒Fe‒Ni wires with different composition gradients, deposited into polycarbonate track-etched membranes. The effect interfaces and concentration gradients have on the effective fields of the investigated wires is examined. An anomalous angular dependence of the fields of ferromagnetic resonance is observed for the wire arrays at a pore density of 18

We discussed experimental results concerning the ferromagnetic resonance spectra characteristics of Co-Ni and Co-Fe-Ni wires arrays with different gradients of composition deposited into porous of track etched polycarbonate membranes. The influence of interfacial boundaries and concentration gradients on the effective field of the investigated wires has been studied. An anomalous angular dependence of the FMR resonance fields is observed for wires arrays with a membrane pore density of ~18%.

The study investigates carbon-containing coatings of 3d-metals (Ni, Co, Fe) produced by chemical deposition method using arabinogalactan. The coatings were analyzed using X-ray diffraction, FMR, and M(H) magnetometry. Measurement of M(H) in plane and perpendicular to the plane of the magnetic coatings allowed determining the distribution of demagnetizing factor in the studied coatings. The obtained distributions of the demagnetizing factor were used to analyze the angular dependences of the ferromagnetic resonance field. The values of magnetization and perpendicular anisotropy field were estimated. The paper illustrates the effect of texture on the magnetic parameters.

By the example of α-Fe2O3 hematite, 5Fe2O3⋅9H2O ferrihydrite, and γ-Fe2O3 maghemite powders, a microwave-radiation-induced powder system temperature growth ΔTmax of several degrees has been measured in the ferromagnetic resonance mode at a frequency of 8.9 GHz. The powders heat up the most in the external field H coinciding with the ferromagnetic resonance field. The value of the ΔTmax effect depends on the magnetization of a powder material. The results obtained allow us to propose a new magnetic hyperthermia method for biomedical applications.

Ferrihydrite nanoparticles are synthesized and characterized. The dependences of heating of powders are studied upon pumping by a high-frequency electromagnetic field on a dc magnetic field. It is shown that the experimental dependence of the temperature of particles on a dc magnetic field is consistent with the theory of ferromagnetic resonance for an isotropic superparamagnet.

Nickel and cobalt ferrite nanoparticles have been synthesized using the chemical precipitation method; the nanoparticle sizes were found to be 63 ± 22 and 26 ± 4 nm, respectively. The static hysteresis loops and Mössbauer spectra have been measured. It is shown that cobalt ferrite powders are magnetically harder than nickel ferrite powders. Ferromagnetic resonance (FMR) curves have been studied. It is found that the FMR absorption for cobalt ferrite is observed at room temperature and above. The time dependences of the nanoparticle warm-up under FMR conditions have been measured. The maximum temperature changes for nickel ferrite and cobalt ferrite particles are 8 and 11 K, respectively. Using the example of cobalt ferrite powder, the possibility of effectively heating of particles in the FMR mode in their own field without using a DC magnetic field source is shown. The observed effect can be used in magnetic hyperthermia.

Nickel ferrite nanoparticles 4 nm in size were synthesized by chemical deposition. Subsequent annealing at T=700 o C for 5 h led to an increase in the particle size to 63 nm. The Mossbauer spectra and the frequency-field dependences of ferromagnetic resonance have been measured. It has been shown that freshly prepared powders are superparamagnetic at room temperature. The kinetic dependences of the heating of nanoparticles in the ferromagnetic resonance mode at a frequency of 8.9 GHz were measured. It was found that the maximum rate of temperature increase in this mode for a ferromagnetic powder is an order of magnitude greater than for the superparamagnetic state (1.2 and 0.13 K/s, respectively). The latter is determined by the saturation magnetization of the studied powders. Keywords: ferromagnetic resonance, superparamagnetic powders, relaxation frequency, frequency-field dependence, heating of powders.

Nickel ferrite nanoparticles 4 nm in size were synthesized by chemical deposition. Subsequent annealing at T=700℃ for 5 h led to an increase in the particle size to 63 nm. The Mössbauer spectra and the frequency-field dependences of ferromagnetic resonance have been measured. It has been shown that freshly prepared powders are superparamagnetic at room temperature. The kinetic dependences of the heating of nanoparticles in the ferromagnetic resonance mode at a frequency of 8.9 GHz were measured. It was found that the maximum rate of temperature increase in this mode for a ferromagnetic powder is an order of magnitude greater than for the superparamagnetic state (1.2 and 0.13 K/s, respectively). The latter is determined by the saturation magnetization of the studied powders.

The structural and magnetic properties of nanostructured Fe 100-x Ni x -C (0<x<100) coatings produced by electroless plating with different carbohydrates as reducing agents have been investigated. The phase-structural state of the films was studied by diffraction and electron microscopy. The Ni concentration ranges of FCC and BCC phases existence in electroless deposited films were determined. The surface morphology, saturation magnetization, local magnetic anisotropy field and coercivities of films are dependent on the iron content and type of reducing agent. The correlation between coercivity H c and the anisotropy field of the magnetic stochastic domain which were established by correlation magnetometry suggests that the magnitude of H c is mainly determined by this anisotropy. Keywords: 3d-metal alloys, the approach to saturation magnetization law, coercivity.

The structural and magnetic properties of nanostructured Fe-Ni‒C coatings produced by electroless plating with different carbohydrates as reducing agents have been investigated. The phase-structural state of the films was studied by X-ray diffraction and electron microscopy. The Ni concentration ranges of FCC and BCC phases existence in electroless deposited Fe-Ni‒C films were determined. The surface morphology, saturation magnetization, local magnetic anisotropy field and coercivities of FeNi-C films are dependent on the iron content and type of reducing agent. The correlation between coercivity and the anisotropy field of the magnetic stochastic domain which were established by correlation magnetometry suggests that the magnitude of Hc is mainly determined by this anisotropy

Powders of maghemite γ-Fe 2 O 3 with an average diameter of 8 nm, γ-Fe 2 O 3 /SiO 2 composites with an agglomerate diameter of about 50 nm and a size of interspersed γ-Fe 2 O 3 particles of 6 nm, and γ‑Fe 2 O 3 /SiO 2 /aptamer(FAS9) composites were synthesized by chemical deposition. Mössbauer spectra were measured, the static and dynamic magnetic properties of the powders were studied, and the coercive force was determined, which decreases from 14 Oe for γ-Fe 2 O 3 powders to 3 Oe for the γ-Fe 2 O 3 /SiO 2 composite. It is shown that the particle blocking temperature is close to room temperature. The increment of temperature of the powders was measured in the ferromagnetic resonance mode; the temperature of the Fe 2 O 3 /SiO 2 composite (Δ T ≈ 16°C) turned out to be higher than that of the pure γ-Fe 2 O 3 powder (Δ T ≈ 10°C). It has been experimentally shown that temperature increment Δ T is proportional to the square of the microwave field amplitude. It has been shown that the composition γ-Fe 2 O 3 /SiO 2 /aptamer FAS9 is able to effectively bind to tumor cells, and FMR hyperthermia leads to a decrease in the viability of tumor cells.

The article considers the features of the influence of wind load in the Arctic and Far North regions on the static and dynamic state of direct waveguides. Waveguides have a thin-walled design with restrictions on wall deflections, so the theory of plates and shells is used to calculate them. In the static state, the wind load is modeled by uniform pressure on one side of the waveguide. This made it possible to obtain an analytical solution to the problem by the plate theory, identify the features of the stress distribution over the waveguide structure, and clarify the solution compared to the beam theory. Comparing the results of the calculation according to the proposed method with the results of beam theory showed good convergence. The dynamic state was estimated by the first natural frequency of waveguides, considering ice deposits. The results of the calculations showed a significant impact of ice deposits on the frequency of oscillations and showed the need for deicing.

In this paper, we conduct research of the waveguide strength under icing. Icing is assumed to be uniform along the perimeter and length of the waveguide, so ice deposits is considered in the form of an equivalent increase in the density of the structure. As a result, the icing problem is reduced to the problem of gravitational bending of the waveguide. Waveguide has a thin-walled rectangular cross-section; therefore, a solution demand using the theory of plate. We model the waveguide in the form of 4 plates that made it possible to obtain an analytical solution to the problem according to the plate theory. Also, it makes possible to identify the features of the stress distribution both in length and in the height of cross-section of the waveguide and refine the results in comparison with the theory of beams. The results of analytical calculation according to the developed method is compared with the data obtained according to beam theory, which show good convergence with the data obtained according to beam theory, which showed good convergence.

A porous polymer loaded with segmented nanorods of magnetic metal is very promising for the design of novel microwave devices. Arrays of bi-segmented Ni/Co and core–shell Ni@Co rods were prepared by electroless deposition into porous of polycarbonate track-etched membrane. An intrinsic effective magnetic field of the magnetic composite nanorods aligned in the nonmagnetic template was studied by magnetization curves and ferromagnetic resonance (FMR). The effect of the interface boundaries for two types of bi-segmented rods with coaxial and along-axis Co/Ni segmentation to effective field was established.

The paper has considered the problem of determining the stress state of thin-walled waveguide structures during torsion. An analytical solution using the Bredt’s formula has been considered and its comparison with a numerical solution using the finite element method has been performed. The numerical solution has been carried out using a created volume model, and the load has been modeled as a set of concentrated forces distributed over the entire cross-section of the waveguide. It has allowed us to reduce the local effects in the form of complex stress state and increase the accuracy of the results. Comparison of the results has shown that the stresses calculated by the finite element method are always higher than those obtained by the Bredt’s formula and it is necessary to take into account their maximum values. The deformation evaluation also has shown that the FEM calculations give larger twist angles than those obtained by the Bredt’s formula for all the considered section sizes.

This paper proposes a method for determining the required gap between the elements of the waveguide path during its assembly by soldering. The need for a thermal gap is defined by difference in mass and dimensional parameters of the elements to be connected, due to which a significant no uniformity of heating and thermal deformations occur. The no uniformity of thermal deformations leads to jamming of one element in another, therefore, the heating time and the size of the thermal gap are need to be determined. The diameter of the solder wire is determined according to the size of the thermal gap and the required fillet of the soldered seam. The performed numerical calculations of the stress state of the obtained soldered seam showed the absence of stress concentration. Mechanical tests have confirmed the high strength of soldered seam.

The dipole-dipole interaction effect on the magnetic hysteresis of nanoparticles randomly dispersed within a plane is studied by micromagnetic simulation. The dependence of the coercive field with the concentration of nanoparticles varies from nonlinear and monotonic to non-monotonic dependence with a maximum at a certain concentration. It happens when the ratio of the magnetic anisotropy constant to the maximal dipole energy changes from value much larger than 1 to the value much less than unity.