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  • On the mechanism of formation of hexagonal ferrite BaFe12-hAlxO19

    The paper discussed the mechanism of formation of polycrystalline hexagonal barium ferrite. The influence of alloying elements on the location of Fe3 hexagonal block R, on the border of hexagonal and spinel blocks (RS). It is shown that the presence of weakly diamagnetic ions or dopants in these positions provides specific properties of hexagonal ferrites and their practical use.

    Keywords: hexaferrite barium, dopant, magnetic properties, the mechanism of formation, anisotropy, polycrystalline, magnetization, Mossbauer spectroscopy, the coercive force, Curie temperature

  • Magnetic properties of multiferroics BiFeO3, (BiLa)FeO3 and (BiNd)FeO3 electrets formed by corona discharge

    Recently, BiFeO3  multiferroics have drawn a great deal of attention due to their superior ferroelectric properties in epitaxial thin film form in comparison to counterpart bulk single crystals or ceramics. In this work we present the results on magnetic properties of multiferroic ultrathin films (30-300 nm) of BiFeO3, (BiLa)FeO3 and  (BiNd)FeO3  obtained by sputtering in transverse high frequency discharge, vacuum laser oblation and metalorganic chemical vapour deposition  on monocrystalline  substrates of (001) SrTiO3, (100) MgO and  (100) Al2O3. The concentration of Bi, La и Nd in dodecahedral sublattices was varied. A novel effect of treatment of multiferroic films in a negative corona discharge has been investigated. It is demonstrated that the magnetisation may be increased by up to 35%  whilst the change in    is not noticeable. This effect does not depend on neither film composition no technological method. 

    Keywords: multiferroics, magneto-electric materials, methods of preparation, the films of bismuth ferrite, pseudomorphic structure, magnetic properties, corona discharge

  • The influence of basic chemical composition on the properties nickel-zinc ferrites, received by radiothermic sintering

    To date, the main method of mass production of advanced functional materials for various purposes is the ceramic technology. In the manufacture of multi-component oxide compounds using of ceramic technology is difficult to achieve high uniformity of chemical composition. For activation of the raw ingredients and make it more uniform use of chemical-tions (co-precipitation of salts or hydroxides, spray drying, Cryochemistry) and physical-tions (mechano-chemical, microwave, ultrasonic) methods. The paper presents the results of work on obtaining Ni-Zn-ferrite 2000NN radiation-thermal sintering. The influence of base composition and alloying additions on the electromagnetic properties of the ferrites. Confirmed the effectiveness of the use of surface-active additives To increase the density of the raw pieces and level parameters. We propose a model that explain schaya efficiency of dopants in the radiation-thermal sintering.

    Keywords: Nickel-zinc ferrite, radiation thermal sintering, base composition, alloying additives, permeability

  • Effect of additives on the properties of the alloy radio-Mg-Zn-ferrite obtained by sintering heat-radiation

    Promising absorbing materials along with a Ni-Zn-ferrites are Mg-Zn-ferrites, as they are also intensively absorbs electromagnetic waves in the frequency range from 50 MHz to 1000 MHz. The main advantage of the Mg-Zn-ferrite is used as an inexpensive raw material magnesium oxide. The paper presents the results of research to improve the efficiency of broadband radio-magnesium-zinc ferrite by increasing the contribution of the dielectric loss. The influence of alloying elements of the atmosphere gas and cooling after the sintering thermal radiation by absorption of electromagnetic waves. Confirmed cooling efficiency of products after sintering in an atmosphere with reduced oxygen partial pressure to increase the dielectric constant. A model is proposed to explain the increase in the dielectric loss ferrite during cooling in a reducing atmosphere.

    Keywords: radioabsorbing ferrites, microstructure grain boundaries radio measurement radiation thermal sintering

  • Thermoactivation current spectroscopy of electrically active centres in epitaxial monocrystalline films of (TmBi)3(FeGa)5O12:Ca2+ ferrite-garnet

    The spectra of thermally stimulated conduction currents (TSCC) in (TmBi)3(FeGa)5O12:Ca2+ ferrite-garnet films have been investigated with the purpose to reveal electrically active centres. The samples were fabricated by liquid phase epitaxy (LPE) from melt solution on the Gd3Ga5O12substrates with the crystallographic orientation (111) with the use of Bi-containing flux (without Pb). Increasing the concentration of Ca2+ions in the films were realised by increasing the concentration of CaO in the melt solution. The obtained films contained Ca2+ ions from 0,03 f.u to 0,1 f.u. With the help of standard thermoactivation current spectroscopy the spectra of the initial samples and samples subjected to ultraviolet radiation and negative corona discharge were obtained. The characteristic parameters of electrically active defects were calculated.

    Keywords: thermally induced electrical current, ferrite garnet films, electrically active centres, deep-level capture, charge compensation, Ca- doping, ТСТП-spectra, temperature position