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.

The results of studies of the features of the phase composition, crystal and magnetic structure of Bi-substituted barium hexaferrite BaFe12-xBixO19 (0.1≤ x≤ 1.2) by methods of Mossbauer spectroscopy, X-ray phase analysis, as well as image analysis by scanning electron microscopy are presented. Samples of Bi-substituted hexaferrites - BaFe12-xBixO19 (where x=0.1; 0.3; 0.6; 0.9 and 1.2) were synthesized by the method of solid-phase reactions with double annealing (at T=1100oC for 6 h) and intermediate grinding (for 0.5 h). The X-ray phase analysis allowed us to establish the limit of substitution of Fe3+ ions by Bi3+ ions. It has been shown that at a low level of substitution (x≤0.3) there are no impurity phases detected and the samples are characterized by a single-phase state with the spatial group P63/mmc. When the degree of substitution increases (x>0.3) the formation of impurity phases is noted, which can be explained by the difficulties of ion diffusion in the process of solid-phase synthesis, as well as the formation of defects in the structure of magentoplumbite due to the large ionic radius of Bi3+. As impurity phases in the studied compositions (x>0.3) Marked: BiFeO3 (Pr. Gr. Pnma); BiO2 (Pr. Gr. Fm-3m); BaBi2O6 (Pr. Gr. R-3) and BaO0,5Bi1,5O2,16 (Pr. Gr. Im-3m). The content of the main phase (Pr. Gr. P63mmc) at the same time decreases from 95.11 to 88.27 vol.% when increasing x from 0.6 to 1.2, respectively. The analysis performed by the method of Messbaurov spectroscopy showed that all Fe ions have a charge of 3+. And all parameters lie within the values characteristic of Fe3+ ions corresponding to the coordination of polyhedra: 12k. 4f2, 2a - octahedra, 4f1 - tetrahedron, and 2b - bipyramide. It is possible to single out a small monotonous decrease only for the 12k position. The analysis of SEM images showed an increase in the average particle size up to 10 mkm, depending on the concentration of bismuth oxide during the synthesis of hexaferrite.

The microscopic mechanism of the occurrence of ferroelectric properties in M-type barium hexaferrites is investigated by experimental and first-principle computation methods. The analysis of magnetic, X-ray, and Mossbauer measurements of BaFe12O19 samples ascertains the correlation between the thermal factor in the process of annealing samples and their functional properties. The occurrence of the remnant polarization in barium hexaferrites at room temperature contradicts the description of their crystal structure in the fra-mework of centrosymmetric space group P63/mmc (No. 194), in which one of the symmetry operations is inversion center. Therefore, the crystal structure of BaFe12O19 was analyzed in the frameworks of SG P63/mmc (No. 194) and non-centrosymmetric SG P63mc (No. 186). The computed value of polarization for a non-centrosymmetric unit cell is similar to 3.5 mu C/cm2. The analysis of polarization was carried out on a path connecting the polar P63mc and non-polar P63/mmc structures and considered in terms of the total energy barrier. Our result allows ascertaining a direct relationship between the remnant polarization of the unit cell and the broken spatial-inversion symmetry in the crystal structure of M-type barium hexaferrite.(c) 2022 Elsevier B.V. All rights reserved.

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.

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.

Nanocomposites (NCs) (100-x) SrFe12O19/x Co (x = 10, 20, and 30 wt. %) were produced using the high energy ball-milling (HEBM) process. The effects of hard/semi-hard ratio and annealing temperature (800, 900, and 1000 °C) on the exchange-spring in magnetic NCs were discussed. X-ray diffraction examination showed the coexistence of M-type hexaferrite SrFe12O19 (SFO) as the hard phase and CoFe2O4 spinel ferrite (CFO) as the semi-hard phase. Using a scanning electron microscope (SEM), the morphology and elemental analysis of the NCs were analyzed. The magnetic performances were investigated via a vibrating sample magnetometer at room temperature. With increasing the CFO content and annealing temperature, the hysteresis loop became narrower and possessed semi-hard magnetic properties. The 10 wt. % Co NCs annealed at 800 °C had the highest coercivity of Hc = 4.2 kOe. These results are correlated with switching field distribution plots that have indicated the efficient exchange-spring between SFO and CFO phases NCs annealed at 800 °C. The studied samples can be a promising candidate in permanent magnets and magnetic recording media applications.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063783421130011

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.

n Erratum to this paper has been published: https://doi.org/10.1134/S1063783421130011

The cation distribution and magnetic properties of polycrystalline ВаFe12–xSnxO19 (х = 0.0, 0.1, 0.3, 0.6, 0.9 and 1.2) ferrites have been studied for the first time by Fe57 and Sn119 Mössbauer spectroscopy. It was shown that doping of BaFe12O19 with tin is performed with limited heterovalent isomorphism according to the scheme 2Fe3+Sn4+ + Fe2+. It was found that intense heterovalent isomorphic substitutions occur in the 12k site of the BaFe12-xSnxO19 hexaferrite in the range of 0.1 < x < 0.6; less significant substitutions observed in the 4f2 and 2a sites. It was established that the heterovalent isomorphic substitution of tin for iron in BaFe12- xSnxO19 is limited by the values of x in range х = 0.6–0.9 Measurements of the magnetic parameters of the obtained samples were performed. The possibility of practical application of the synthesized ferrites is discussed.

BaYxFe12-хO19 (0.1 ≤ x ≤ 1.2) hexaferrites were studied using Mössbauer spectroscopy, magnetometry, and X-ray diffraction. A low isomorphic capacity of hexaferrite is shown, which at x = 0.6 leads to phase separation with the formation of BaFe2O4 and Y3Fe5O12 impurity phases. The data of Mössbauer spectroscopy showed that the Y3 + ions occupied the 12k position with the formation of the nonequivalent position 12k ′ due to the breaking of two magnetic bonds Fe (12k) - O - Fe (12k) in the triad of octahedra 12k with their replacement by Fe (12k ) - O - Y (12k). It is shown that BaYxFe12-хO19 hexaferrites are less magnetically hard than BaFe12-хAlxO19.

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.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063783421130011

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.

The cation distribution and magnetic properties in polycrystalline ferrites of BaFe 12 – x Sn x O 19 ( x = 0, 0.1, 0.3, 0.6, 0.9, and 1.2) are first studied using Mössbauer spectroscopy of Fe 57 and Sn 119 . It is shown that doping of BaFe 12 O 19 with tin is performed with restricted heterovalent isomorphism according to the 2Fe 3+ → Sn 4+ + Fe 2+ reaction. It is found that intense heterovalent isomorphic substitutions in the 12 k position of the BaFe 12 – x Sn x O 19 hexaferrite are in the range of 0.1 < x < 0.6; and less significant substitutions are in the 4 f 2 and 2 a positions. It is found that the limit of heterovalent isomorphic substitution of iron with tin in BaFe 12 – x Sn x O 19 is in the range of x = 0.6–0.9. The magnetic parameters of the samples are measured. The possibility of practical application of the synthesized ferrites is discussed.

Using Mössbauer spectroscopy, magnetometry and X-ray diffraction, we have studied the BaYxFe12 – xO19 hexaferrite (0.1 ≤ x ≤ 1.2). The low isomorphic capacitance of hexaferrite is shown, which leads to phase separation with the formation of ВаFe2O4 and Y3Fe5O12 for x = 0.6. Mössbauer spectroscopy data have shown that, in the studied range of substitutions, Y3+ ions enter the 12k position with the formation of a nonequivalent 12k' position due to the breaking of two Fe(12k)–O–Fe(12k) magnetic bonds in the 12k octahedron triad with their replacement by Fe(12k)–O–Y (12k). The BaYxFe12 – xO19 hexaferrite has been shown to be less magnetically hard than BaFe12 – xAlxO19.