the article discusses the electromagnetic absorbing and shielding properties of ferrite-polymer composites of the composition Mn–Zn ferrite/fluoroplast-42, obtained by pressing a mixture of powders with heating. The measurement of the complex magnetic and dielectric permittivity spectra, as well as the reflection coefficient spectra was carried out in the frequency range 0.1–7 GHz. Using the obtained spectra, a comprehensive analysis of the absorbing characteristics of the composites was carried out, and the factors responsible for the absorption were determined. Fitting of the composites magnetic permeability spectra show that the process of natural ferromagnetic resonance prevails over the resonance of domain walls, and a decrease in the concentration of ferrite inclusions leads to a significant shift in the frequency of natural ferromagnetic resonance to high frequencies. It was found that for composites with a thickness of 5–10 mm, compositions with a mass fraction of ferrite ≤ 0.4 show radio-absorbing properties, while compositions with a fraction of ≥0.6 show shielding properties.

The electromagnetic and radio-absorbing characteristics offerrite-polymer composites with conductive inclusions based on polyvinylalcohol are investigated. The Ni-Zn spinel ferrite powder of 2000NN gradewith composition Ni0.32Zn0.68Fe2O4 was used as filler. It is shown that theobtained composites are effective absorbers in the frequency range of 2-5 GHz with peak reflection loss less than ~20 dB. Through the analysis of thepermittivity spectra and permeability spectra, as well as the calculatedreflection loss spectra, critical factors of the electromagnetic waveabsorption in obtained composites are established. Keywords: polymer composite, radio absorption, nickel-zinc ferrite,polyvinyl alcohol\

The article describes electromagnetic and microwave properties of the polymer composite with the lithium spinel ferrite inclusion of composition Li0.33Fe2.29Zn0.21Mn0.17O4 in the frequency range 100-7000 MHz. It is shown that samples with a mass fraction of ferrite 60, 80% have pronounced radio-absorbing properties, measured using the reflection coefficient on a metal plate (return losses). For a composite with 80% ferrite, the minimum return loss was -37.5 dB at 2.71 GHz with an absorption width at -10 dB of 3 GHz. High absorption characteristics are directly related to the use of ferroelectric polymer P(VDF-TFE) as a binder, which is expressed in the combined action of the absorption mechanisms of the magnetic and ferroelectric phases. Keywords: lithium ferrite, polymer composite, polyvinylidene fluoride, radio-absorbing material.

The article discusses the electromagnetic absorbing and shielding properties of ferrite-polymer composites of the composition Mn-Zn ferrite/fluoroplast-42, obtained by pressing a mixture of powders with heating. The measurement of the complex magnetic and dielectric permittivity spectra, as well as the reflection coefficient spectra was carried out in the frequency range 0.1 - 7 GHz. Using the obtained spectra, a comprehensive analysis of the absorbing characteristics of the composites was carried out, and the factors responsible for the absorption were determined. Fitting of the composites magnetic permeability spectra show that the process of natural ferromagnetic resonance prevails over the resonance of domain walls, and a decrease in the concentration of ferrite inclusions leads to a significant shift in the frequency of natural ferromagnetic resonance to high frequencies. It was found that for composites with a thickness of 5 - 10 mm, compositions with a mass fraction of ferrite ≤ 0.4 show radio-absorbing properties, while compositions with a fraction of ≥ 0.6 show shielding properties.

Samples of BaFe12O19 M-type barium hexaferrite with partial iron substitution by zirconium ions (concentration up to 10 at.%) have been synthesized and investigated. Studies of crystal features, phase composition, and magnetic properties were carried out using X-ray diffraction, Messbauer spectroscopy, and VSM respectively. The presence of limited heterovalent isomorphism by the 2Fe3+->Zr4++Fe2+ mechanism was shown. The limit of heterovalent isomorphic substitution by zirconium ions in barium hexaferrite (x=0.6) was established. It was noted that additional sextets in the Messbauer spectra of barium hexaferrite can be formed during the localization of Zr4+ ions predominantly in the 12k and 4f2 positions due to the frustration of the magnetic structure. The correlation between the chemical composition (concentration of zirconium ions), impurity phase formation, the peculiarities of the distribution of substituents over oxygen coordination, and the magnetic properties was established. Keywords: M-type barium hexaferrite, heterovalent substitution, limited isomorphism, Messbauer spectroscopy, magnetic properties

Samples of BaFe12O19 M-type barium hexaferrite with partial iron substitution by zirconium ions (concentration up to 10 at.%) have been synthesized and investigated. Studies of crystal features, phase composition, and magnetic properties were carried out using X-ray diffraction, Mössbauer spectroscopy, and VSM respectively. The presence of limited heterovalent isomorphism by the 2Fe3+ → Zr4+ + Fe2+ mechanism was shown. The limit of heterovalent isomorphic substitution by zirconium ions in barium hexaferrite (x = 0.6) was established. It was noted that additional sextets in the Mössbauer spectra of barium hexaferrite can be formed during the localization of Zr4+ ions predominantly in the 12k and 4f2 positions due to the frustration of the magnetic structure. The correlation between the chemical composition (concentration of zirconium ions), impurity phase formation, the peculiarities of the distribution of substituents over oxygen coordination, and the magnetic properties was established.

The electromagnetic and radio-absorbing characteristics of ferrite-polymer composites with conductive inclusions based on polyvinyl alcohol are investigated. The Ni-Zn spinel ferrite powder of 2000NN grade with composition Ni0.32Zn0.68Fe2O4 was used as filler. It is shown that the obtained composites are effective absorbers in the frequency range of 2⸺5 GHz with peak reflection loss less than –20 dB. Through the analysis of the permittivity spectra and permeability spectra, as well as the calculated reflection loss spectra, critical factors of the electromagnetic wave absorption in obtained composites are established.

Electrophysical properties of polyvinyl alcohol / Mn–Zn ferrite composites are studied in the 0.05–7 GHz range of frequencies. It is found that the concentration of ferrite determines the values of dielectric permittivity and magnetic permeability. It is shown that composites with ferrite fractions of 0.2 and 0.4 can be used as radar absorbing materials, while those with fractions of 0.6 and 0.8 can be used as radio shielding materials.

The article describes electromagnetic and microwave properties of the polymer composite with the lithium spinel ferrite inclusion of composition Li0.33Fe2.29Zn0.21Mn0.17O4 in the frequency range 100 MHz - 7000 MHz. It is shown that samples with a mass fraction of ferrite 60, 80% have pronounced radio-absorbing properties, measured using the reflection coefficient on a metal plate (return losses). For a composite with 80% ferrite, the minimum return loss was -37.5 dB at 2.71 GHz with an absorption width at -10 dB of 3 GHz. High absorption characteristics are directly related to the use of ferroelectric polymer P(VDF-TFE) as a binder, which is expressed in the combined action of the absorption mechanisms of the magnetic and ferroelectric phases.

Polycrystalline spinel ferrites with a composition of Li 0.33 Fe 2.29 Zn 0.21 Mn 0.17 O 4 have been synthesized using the ceramic technology at sintering temperatures of 950, 1000, 1050, and 1100°C. The magnetic hysteresis loops and permeability of the objects of study are analyzed in magnetic fields from –400 to +400 A/m. The behaviors of the complex permittivity and complex permeability and the reflectance on a metal plate are investigated in the frequency range of 0.01–7.0 GHz. It is established that the optimal range of sintering temperatures for the synthesized ferrites is from 1050 to 1100°C. It is shown that the Li 0.33 Fe 2.29 Zn 0.21 Mn 0.17 O 4 spinel ferrite intensely absorbs electromagnetic radiation in the frequency range of 0.05–7.0 GHz. Possibilities of practical application of the results obtained are discussed.

Polycrystalline spinel ferrites of the composition Li0.33Fe2.29Zn0.21Mn0.17O4 were synthesized by using the ceramic technology method at sintering temperatures of 950 ° C, 1000 ° C, 1050 ° C, and 1100 ° C. Magnetic hysteresis loops and magnetic permeability of the experimental samples were studied in the range of magnetic fields of -400–400 A/m. In the frequency range of 0.01–7.0 GHz, the behavior of the complex dielectric and complex magnetic permeability, as well as the reflection coefficient on a metal plate, are investigated. It was found that the optimal sintering temperature range for synthesized ferrites is from 1050 ° C to 1100 ° C. It is shown that the spinel ferrite Li0.33Fe2.29Zn0.21Mn0.17O4 intensely absorbs electromagnetic radiation in the frequency range from 0.05 to 7.0 GHz. Possibilities of practical application of the obtained results are discussed.

In this paper the electrical and dielectric properties of polycrystalline yttrium iron garnet, obtained by the radiation-thermal sintering technology in a fast electron beam were investigated. Spectra of complex dielectric constant, dielectric loss tangent and conductivity were measured in the frequency range 25 – 1∙106 Hz. For comparison, DC resistance measurements were also performed. The temperature dependences of the above parameters were measured at frequencies of 1 kHz, 100 kHz in the range 25 - 300 °C. It is shown, that conduction activations energy, permittivity, loss tangent and resistance vary significantly from sintering temperature in the range of 1300 to 1450 °C. It is found that with an increase in the sintering temperature to 1450 °C, dielectric properties are the same as samples made by the traditional ceramic technology.

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.

Electrical and dielectric properties of polycrystalline yttrium–iron garnet samples grown by the technology of radiation-thermal sintering in the fast electron beam are considered. In the frequency range from 25 Hz to 1 MHz, the normal complex permittivity, dielectric loss tangent, and ac conductivity spectra are measured. For comparison, in addition to frequency measurements, dc resistivity is measured. The temperature dependences of the above parameters are also measured at frequencies of 1 and 100 kHz in the temperature range of 25–300°C. The activation energies of the ac and dc conduction processes on the Arrhenius coordinates are determined by the temperature dependences of the conductivity. It is shown that as the sintering temperature increases from 1300 to 1450°C, the electrical parameters reach values characteristic of samples grown by conventional ceramic technology.

Samples of polycrystalline yttrium-iron garnet synthesized using radiation-thermal sintering and ceramic processing have been studied by the Mössbauer spectroscopy method. The best decomposition of the Mössbauer spectroscopy spectra of the research objects, which is a simulation of the experimental spectrum with five sextets, has been selected. An additional fifth sextet is caused by Fe3+ ions, which are surrounded by oxygen vacancies leading to distortion of Fe-tetrahedra, which is reflected in an increase in the quadrupole splitting of Fe3+. An increase in the density of s-electrons on Fe ions in distorted tetrahedra has been found, resulting in a decrease in the isomeric chemical shift δ of Fe ions to a value close to the δ value for Fe4+ ions. It has been shown that the optimal crystal structure is realized in Y3Fe5O12 polycrystals when they are sintered for 40–60 min in the temperature range of 1350–1400°C by the radiation-thermal sintering method.

The Mössbauer spectroscopy (MS) method was used to study polycrystalline iron yttrium garnet (YIG) samples synthesized by radiation thermal sintering (RTS) technology and by standard ceramic technology (CT). The best option for decomposing the MS spectra of the objects of study was selected, which is a model of the experimental spectrum with five sextets. An additional fifth sextet is caused by Fe3 + ions, surrounded by oxygen vacancies which lead to distortion of the Fe tetrahedra which reflected by an increase in the quadrupole splitting of Fe3+. An increase in the density of s-electrons on Fe ions in distorted tetrahedra lead to a decrease in the isomeric chemical shift δ of Fe ions up to a values closed to the δ value for Fe4+ ions. It was shown that the optimal crystalline structure realizes for Y3Fe5O12 polycrystals upon sintering by RTS method in the temperature range of 1350–1400 ° C for a time from 40 to 60 min.

In this work the crystal structure and texture of isotropic and anisotropic polycrystalline hexagonal ferrites BaFe 12 O 19 obtained by the method of radiation-thermal sintering (RTS) is studied using X-ray diffraction and X-ray phase analysis. Crude blanks of both isotropic and anisotropic hexaferrites are obtained by the standard method of ceramic technology from the same raw material (Fe 2 O 3 and BaCO 3 of the analytical grade brand) and on the same equipment with the only difference being that the anisotropic blanks were pressed in the magnetic field H = 10 kOe. For sintering raw billets, a linear electron accelerator ILU-6 (electron energy E e = 2.5 MeV) is used (Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences). The samples are sintered in air for one hour at 1200, 1250, 1300, and 1350°C. It is shown for the first time that high-quality single-phase isotropic and anisotropic hexaferrites BaFe 12 O 19 can be obtained from raw blanks of a ferritized charge using the RTS technology. The properties of the crystal structure and texture of the obtained objects of the research are described. It is established for the first time that the dependence of the pref.orient.o1 predominant orientation of the crystal texture parameter on the degree of the magnetic texture f in polycrystalline hexagonal barium ferrites of type M is described by the expression pref.orient.o1 = –0.005 f + 0.6886.