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BaFe12O19 nanofilms with uniaxial texture have been synthesized by ion-beam deposition with subsequent annealing. Silicon wafers with sublayers of amorphous alumina (Al2O3), silicon nitride (Si3N4), and their combinations have been used as substrates. The films have been studied by X-ray diffraction and atomic force microscopy. It has been confirmed that hexaferrite with its c axis perpendicular to the plane of the substrate is spontaneously formed on the amorphous surface of Al2O3/Si3N4/Si. The BaFe12O19 films grown on Si3N4 sublayers are characterized by the presence of high strain, leading to the destruction of the ferrite coating after crystallization annealing. The annealed BaFe12O19/Al2O3/Si sample contained additional phases; no signs of the (00l) hexaferrite texture were found.

Textured ZnO films obtained on amorphous substrates using the ion-beam sputtering method are studied. X-ray diffraction and atomic-force microscopy methods show that the resulting films have a polycrystalline structure immediately after deposition. It is established that further annealing of the samples in the temperature range from 200°C to 500°C results in recrystallization, which leads to changes in the grain size and surface roughness. A dependence of the crystallization intensity on the deposition conditions is found, which is related to the number of defects in the unannealed films. In films with an initially more perfect structure, heat treatment at 500°C results in the growth of grains by more than 2 times and a decrease in the roughness by ∼40%.

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.

Using Mossbauer 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. Mossbauer 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.

Coatings made of the materials that effectively absorb radiation, e.g., ferrite materials, are used to reduce the level of electromagnetic radiation in rooms containing household or industrial equipment. It is known that significant dissipation of the radiation energy is provided by the thickness of the shielding coating which should be comparable to the length of the electromagnetic wave in the material which, in turn, significantly decreases at high values of the magnetic permeability and permittivity of the radio-absorbing material. Ferrite radio-absorbing coatings are characterized by the high heat resistance, low flammability and small (10 – 20 mm) thickness. However, at frequencies less than 40 MHz, plates with a thickness of more than 30 mm are to be used to provide the effective absorption, and the weight and cost of the coatings increase significantly. The results of studying the effect of the sintering temperature and micro-additives of titanium, calcium and bismuth oxides on the dielectric constant of Ni- and Mn-Zn radio-absorbing ferrites are presented. Reactively pure starting oxide components with a basic substance content of more than 99.6 % wt. were used to synthesize samples using traditional oxide technology. It is shown that alloying with bismuth and titanium oxides is rather effective for obtaining radio-absorbing ferrites with a combination of high values of the magnetic permeability and dielectric permittivity. The obtained results can be used in production of ferrite radio- absorbing materials operating in the megahertz range.

Samples of polycrystalline yttrium-iron garnet synthesized using radiation-thermal sintering and ceramic processing have been studied by the Mossbauer spectroscopy method. The best decomposition of the Mossbauer 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.

This paper presents a detailed study of the magnetic and crystal structures of BaFe12 –xZnxO19 (0.25 ≤ x ≤ 1.5) Zn-substituted barium hexaferrite by Mossbauer spectroscopy, vibrating sample magnetometry, and X-ray diffraction. Partial heterovalent substitution of Zn2+ ions for Fe3+ ions demonstrates limited heterovalent isomorphism according to the scheme 2Fe3+ → Zn2+ + Fe4+, which satisfies the electroneutrality constraint. Mossbauer spectroscopy results indicate the presence of Fe4+ in the BaFe12 –xZnxO19 materials. The heterovalent isomorphous substitution limit has been determined to be x = 1.0. The formation of a zinc spinel has been shown to begin at x = 0.50 and its content increases with increasing zinc content. Data are presented on the predominant character of the substituent ion (Zn2+) distribution in the structure of barium hexaferrite. A correlation has been found between the chemical composition, phase separation, anisotropy of properties, and the temperature of the magnetic phase transition of BaFe12 –xZnxO19 (0.25 ≤ x ≤ 1.5).

Films of microwave-absorbing ferrite-polymer composites comprising 5–50 vol % inclusions were synthesized. X-ray powder diffraction analysis showed that the obtained films are a two-phase composite and contain no other phases but the ferrite and the polymer. Differential scanning calorimetry suggested that the polymer matrix degrades at a temperature above 100°C. The IR spectra of the composites indicated an increase in the crystallinity of the polymer with increasing ferrite content. In the composite containing 40 vol % ferrite, the metal plate reflection coefficient increases to –25 dB at a frequency of 3.2 GHz. Measurements of the permittivity and the electrical conductivity in the frequency range 100 Hz–1 MHz demonstrated that the real part of the permittivity increases with increasing content of the magnetic phase, whereas the electrical conductivity remains unchanged.

The features of the composition, crystal, and magnetic structure of Ti-substituted barium hexaferrite BaFe12 – xTixO19 (0.25 ≤ x ≤ 1.5) are studied by Mossbauer spectroscopy, vibration magnetometry, X-ray diffraction, and simultaneous thermal analysis. Bounded heterovalent isomorphism implemented by the scheme 2Fe3+ → Ti4+ + Fe2+ while retaining the charge balance is established when Fe3+ ions are partially substituted with Ti4+ ions. An increase in the 3d-electron density and the presence of Fe2+ in BaFe12 – xTixO19 samples with x = 1.5 is detected by Mossbauer spectroscopy. The heterovalent isomorphic substitution limit is determined to be within 0.75 < x < 1.0. Using Mossbauer spectroscopy and X-ray diffraction, the formation of titanium-contained phases at x = 1.0 whose content increases with the degree of substitution is shown. The data on the preferential distribution of substituent ions (Ti4+) in the barium hexaferrite structure at the 12k and 2b sites are presented.

The new flavonoid diglycoside thamiflaside was isolated from the aerial part of Thalictrum minus. The chemical structure of this glycoside was determined as apigenin 7-O-α-L-2″′-methoxyrhamnopyranosyl-(1→6)-β-D-glucopyranoside based on PMR and 13C NMR (DEPT, HSQC, HMBC) physicochemical methods.

This article discusses the influence of substitution with Al3+ ions on the field of the effective magnetic anisotropy HAeff and the degree of magnetic texture f of anisotropic polycrystalline hexagonal ferrites of barium and strontium. Sample batches are produced by ceramic technology, the texture is formed by compaction in a magnetic field. The preparation of test objects is described in detail. Batches of barium hexaferrites with an ion concentration of Al3+ 0.9, 1.4, 2.5, and 2.6 f.u. and batches of strontium hexaferrites with a concentration of 0.1 f.u. are synthesized. It is demonstrated that the applied procedure makes it possible to obtain barium and strontium hexaferrites with HAeff = 19–35 kE and f = 80–83%. The mentioned values of HAeff and f are sufficient for the production of substrates for microstrip UHV devices of the millimeter wave band. For the first time, it is detected that the degree of the magnetic texture of polycrystalline barium hexaferrites increases with the concentration of Al3+ ions; in addition, a moderate magnetic texture (5.5–5.8%) is observed in isotropic strontium hexaferrites. The experimental results are discussed. The formation mechanism of the magnetic texture in the considered hexaferrites during synthesis is proposed.

In this work the crystal structure and texture of isotropic and anisotropic polycrystalline hexagonal ferrites BaFe12O19 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 (Fe2O3 and BaCO3 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 Ee = 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 BaFe12O19 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 = –0.005f + 0.6886.

—We have studied the effect of Sc3+ substitution for Fe3+ ions on the magnetic properties and crystal structure of BaFe12– xScxO19 hexaferrites. Based on Mossbauer spectroscopy data, we have assessed the distribution of scandium ions over sublattices and their effect on magnetic characteristics of the materials. The specific magnetization and coercive force of the ferrites have been shown to depend on the location and concentration of scandium ions in the crystal structure. The hexaferrite with x > 0.6 has been found to have a noncollinear magnetic structure.

The effect of the indium dopant on the magnetic properties and crystal structure of M-type barium hexaferrite was studied. Relying on Mossbauer spectroscopy data and magnetic measurements, the distribution of the dopant ions in the sublattices and their effect on magnetic characteristics were established. The dependences of specific magnetization and coercivity on the location of indium ions in the hexaferrite crystal structure and on the indium ion content were determined. Weakening of the exchange interaction between the sublattices at the replacement factor x = 0.6 and change in the magnetic moment orientation determined by the angle θ were revealed.

In this work we have considered metrological problems and measurement of magnetic parameters and presented methods of measuring effective magnetic anisotropy field HAeff and ferromagnetic resonance bandwidth ∆H in magnetically uniaxial hexagonal ferrites in the electromagnetic microwave working frequency range. The methods allow measuring HAeff in the 10–23 and 28–40 kE ranges and ∆H in the 0.5–5.0 range. One method (suitable for wavelength measurements in free space in the 3-mm wavelength range) has been implemented for the 78.33–118.1 GHz range. The other method (based on the use of microstrip transmission lines) has been implemented for the 25–67 GHz range. The methods have been tested for polycrystalline specimens of hexagonal barium and strontium ferrites with nominal composition or complex substituted and having high magnetic texture. The measurement results have been compared with those obtained using conventional measurement methods and spherical specimens. Our methods prove to be highly accurate and reliable.

Polycrystalline BaFe12- x Sc x O19 hexaferrites ( x = 0.1, 0.6, and 1.2), produced using ceramic technology, have hexagonal structure with space group (P63/mmc) as determined by neutron powder diffraction. Magnetic properties were analyzed by vibrating sample magnetometry and Mossbauer spectroscopy. Tuning the magnetic parameters by Sc substitution is associated with several factors: first, ordering the Sc3+ ions in positions 2 b and 4 f 2 and the cation vacancies at the boundary of the spinel and hexagonal blocks; second, transfer of spin density from Fe ions localized at position 12 k to 3 d orbitals of Sc3+ ions; third, weakening the indirect exchange interactions between 2 b , 4 f 2, and 12 k sublattices; and finally, presence of a noncollinear magnetic order for Sc concentration x above 0.6.

The effect a pulsed magnetic field has on the crystal structure and macroscopic magnetic parameters of hexagonal ferrites BaFe12O19 and SrFe12O19 are studied. It is shown that changes in the physical properties of ferrites are due to the ordering of cation vacancies on the boundaries of hexagonal and spinel blocks that minimize local distortion of the oxygen polyhedrons. Violation of the collinear ordering of the magnetic moments of iron ions in the nonequivalent positions of SrFe12O19 ferrite is observed, due to the selective localization of such vacancies (and thus violations of the magnetic relationships in Fe–O–Fe).

In this work structural studies of BaFe12O19/Al2O3/Si3N4 thin films with different thicknesses of aluminum oxide and silicon nitride are represented. It is shown that barium hexaferrite crystallizes on the amorphous surface of aluminum oxide with spontaneously formed (00l) uniaxial texture. Microstructural differences in BaFe12O19 films were observed with varying of the thickness of amorphous sublayers, which is explained by the effect of mechanical stress.

BaFe12O19 films on Al2O3 (001) substrates were synthesized by ion beam deposition with post-annealing. Three deposition regimes were applied, resulting in unique surface morphology and X-ray diffraction patterns of obtained samples. In the first case, the deposition process was interrupted several times and the sample was subjected to ex situ annealing at 900 °C after each interruption. As a result, a film with high texture degree (about 97 %) was obtained. In the second case, the deposition process was interrupted the same number of times, but during each pause the film remained in the vacuum chamber for 10 min at 300 °C. This approach resulted in a medium texture degree of the sample (about 72 %). In the third case, there were no breaks in the deposition process and the texture of the resulting film was extremely poor. An explanation for the observed differences is proposed. To improve the texture of the films, a second annealing at 1280 °C for 10 h was applied, but as a result strong interdiffusion and misorientation of the grains occurred.

Barium hexaferrite thin films were prepared by ion beam deposition on sapphire (1 0 2) single crystal substrates. The structural properties of the films were analyzed by means of X-ray diffraction, atomic force microscopy, magnetic force microscopy and scanning electron microscopy. The obtained results were interpreted as a presence of layered structure with different types of texture and its formation mechanism is proposed. The significant influence of BaFe12O19 thickness on its microstructure was observed. Films obtained under certain conditions are potentially fit for further growing of oriented hexaferrite with out-of-plane orientation of c-axis.

The mechanism of formation of polycrystalline hexagonal barium ferrite with diamagnetic substitution with Al and Ga ions is considered. The localization of the dopants (Al and Ga) in hexagonal and spinel blocks is shown. It is found that the main Al – Fe and Ga – Fe substitutions occur in the 12k sublattice. The substitutions break the Fe–O–Fe exchange couples of the 12k sublattice with other sublattices, which leads to the emergence of non-equivalent positions of Fe3+ions, on the basis of which in the Mossbauer spectra with isomorphic aluminum, 7 sextets are identified and with isomorphic gallium – 6. This leads to a decrease in the magnetic parameters of ferrites, such as specific and residual magnetization, Curie temperature. It is shown that aluminum (x=2.1) entry increases the coercive force, magnetic hardness of the hexagonal ferrite, and gallium (x=0.6) entry lowers the coercive force and magnetic hardness. The angles θ between the magnetic moment and the γ-radiation direction in isotropic substituted hexagonal ferrite polycrystals and foil are determined.

We study identities in vector spaces embedded in finite associative linear algebras. We prove that the L-variety generated by the space of second order matrices over a finite field possesses finitely many L-subvarieties. We construct examples of a finite two-dimensional vector space, a finite four-dimensional linear algebra, and a ring consisting of 16 elements that have no finite basis of identities.

The technology of obtaining anisotropic polycrystalline hexagonal ferrites by the thermal radiation sintering is developed. Using the thermal radiation sintering, we obtained the samples of anisotropic polycrystalline hexaferrites BaFe 12 O 19 , BaFe 12–х Al х O 19 (with the Ni, Ti, Mn additives), SrFe 12 O 19 and SrFe 12–х Al х O 19 (with the Ca, Si additives) for the base layers of the microstrip ferrite untying instruments of the short­wave part of the millimeter wavelength range. The essence of the RTS technology is the obtaining, by the method of classical ceramic technology, by pressing in the strong magnetic field, of raw billets with their consequent sintering in the beam of fast electrons. The use of different compositions and alloying additives makes it possible to control the electromagnetic and magnetic properties of hexaferrites. The advantages of the RTS technology consist in high energy efficiency, high values of operating characteristics of the obtained material and low duration of the process of sintering. It was established that the RTS technology may prove to be an alternative technology when obtaining the high­quality polycrystalline hexaferrites M of elementary and complex substituted compositions. Owing to the low energy­ and time costs, high values of the performance parameters, the RTS technology of anisotropic hexaferrites may find wide application when obtaining permanent anisotropic magnets and various miniature SHF­devices.

In 1993, I. P. Shestakov formulated the following question: Are there finite dimensional central simple algebras over a field of characteristic 0 that do not have a finite basis of identities (Dniester notebook, question 3.103)? In this paper, the authors give the positive answer to Shestakov's question.

Nine new compounds that may be of interest as potential biologically active compounds and as materials for further chemical transformation were synthesized from the principal glycoside of Astragalus alopecurus Pall. (Leguminosae) cycloalpioside D and its genin cycloalpigenin D.

Nine new compounds 3–11 were synthesized from the principal glycoside of Astragalus orbiculatus Ledeb. (Leguminosae), cycloorbicoside A, and may be interesting on their own as potential biologically active compounds and synthons for other compounds.

The natural cycloartane triterpenoid cycloasalgenin, which is 20R,24S-epoxycycloartan-3β,6α,25-triol16-one, was partially synthesized in three steps starting from cyclosiversigenin. In addition to the desired product, its 17-epimer was synthesized. The analogous 17-epimer was also prepared from cycloadsurgenin.

The structure of a new cycloartane-type triterpene glycoside, cyclomacroside E, which was isolated from roots of Astragalus macropus Bunge (Leguminosae), was established as 3-O-α-L-rhamnopyranoside,24-O[(β-D-xylopyranosyl)(1→2)-β-D-xylopyranoside]-24R-cycloartan-1α,3β,7β,24,25-pentaol.

The structure of the novel cycloartane triterpene glycoside cyclomacroside A, which was isolated from Astragalus macropus Bunge (Leguminosae) roots, was determined as 3-O-α-L-rhamnopyranoside-24,25-isopropylidenedioxy-24R-cylcoartan-1α,3β,7β-triol.

The structure of the new cycloartane glycoside cyclomacroside D, which was isolated from Astragalus macropus Bunge (Leguminosae) and is 24R-cycloartan-1α,3β,7β,24,25-pentaol 3-O-α-L-rhamnopyranoside–24-O-β-D-xylopyranoside, was proved.

Cycloadsurgenin, 20R,24 S-epoxycycloartan-6α,25-diol-3,16-dione, was partially synthesized in four steps from cyclosieversigenin. Side products with the structures 17E,24S-cycloart-17-en-6α,24,25-triol-3,16-dione and 17Z,24 S-cycloart-17-en-6α,24,25-triol-3,16-dione were obtained in addition to the desired product.

Ten pure compounds, three of which were identified as β-sitosterol, β-sitosterol β-D-glucopyranoside, and D-3-O-methyl-chiro-inositol, were isolated from roots of Astragalus macropus Bunge (Leguminosae). The structure of the new cycloartane triterpenoid cyclomacrogenin B was established as 24R-cycloartan-1α,3β,7β,24,25-pentaol.

It is shown that difference between magnetic properties of hexagonal ferrites BaFe[12]O[19] and SrFe[12]O[19] is connected with difference of electronic configurations of Ba2+ and Sr2+ ions, and their ionic radii. Replacement of Ba2+ ions by Sr2+ ions that are smaller in size effects the degree of distortions of octahedrons located either in a hexagonal R-block or at its boundary with S-block. It contributes to a preferred localization of electrically active vacancies at the boundary of R- and S-blocks

Leonurus cardiaca L. (Labiatae) and L. quinquelobatus Gilib. are used in galenics as sedative and hypotensive agents [1]. Two species of Leonurus are indigenous to Uzbekistan, L. turkestanicus V. Krecz. et Kupr. and L. panceroides M. Pop. [2], and are used as medicinal plants instead of the official species. However, the chemical compositions of these plants have not been reported. This prompted us to study L. turkestanicus. The air-dried aerial part of L. turkestanicus (2 kg) that was collected in Kara-Tepe, Tashkent Oblast on June 30, 2007, during flowering was extracted with MeOH (4 14 L). The MeOH extract was evaporated to a thick condensate and dissolved in MeOH (70%, 1 L). The solution was filtered. The filtrate was evaporated to remove completely MeOH. The solution volume was adjusted to 0.5 L with H2O. The aqueous solution was extracted three times with n-BuOH. The n-BuOH extract was evaporated to dryness and dried. The yield of the n-BuOH extract was 63.42 g. The n-BuOH extract was chromatographed over a column of KSK silica gel with elution successively by CHCl3, CHCl3:MeOH (1, 100:1; 2, 50:1; 3, 10:1), and CHCl3:MeOH:H2O (4, 70:12:1). Fractions eluted by CHCl3 and system 1 contained sterols. System 2 eluted flavonoid 1 (40 mg).

The structure of a new triterpenoid, secomacrogenin B, which was isolated from Astragalus macropus Bunge (Leguminosae) roots and is 24R-9,10-seco-cycloartan-1(10),9(11)-dien-3β,7β,24,25-tetraol, was elucidated.

The structure of the new cycloartane glycoside cyclomacroside B that was isolated from Astragalus macropus Bunge (Leguminosae) was shown to be 1,7-di-O-acetyl-24R-cycloartan-1α,3β,7β,24,25-pentaol 3-O-α-Lrhamnopyranoside-24-O-β-D-xylopyranoside.