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187 results on '"Demina, P. B."'

6. High-temperature intrinsic ferromagnetism in heavily Fe-doped GaAs layers

Author

Kudrin, A. V., Lesnikov, V. P., Danilov, Yu. A., Dorokhin, M. V., Vikhrova, O. V., Demina, P. B., Pavlov, D. A., Usov, Yu. V., Milin, V. E., Kuznetsov, Yu. M., Kriukov, R. N., Konakov, A. A., and Tabachkova, N. Yu.

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

The layers of a high-temperature novel GaAs:Fe diluted magnetic semiconductor (DMS) with an average Fe content up to 20 at. % were grown on (001) i-GaAs substrates using a pulsed laser deposition in a vacuum. The transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy investigations revealed that the conductive layers obtained at 180 and 200 C are epitaxial, do not contain any second-phase inclusions, but contain the Fe-enriched columnar regions of overlapped microtwins. The TEM investigations of the non-conductive layer obtained at 250 C revealed the embedded coherent Fe-rich clusters of GaAs:Fe DMS. The X-ray photoelectron spectroscopy investigations showed that Fe atoms form chemical bonds with Ga and As atoms with almost equal probability and thus the comparable number of Fe atoms substitute on Ga and As sites. The n-type conductivity of the obtained conductive GaAs:Fe layers is apparently associated with electron transport in a Fe acceptor impurity band within the GaAs band gap. A hysteretic negative magnetoresistance was observed in the conductive layers up to room temperature. Magnetoresistance measurements point to the out-of-plane magnetic anisotropy of the conductive GaAs:Fe layers related to the presence of the columnar regions. The studies of the magnetic circular dichroism confirm that the layers obtained at 180, 200 and 250 C are intrinsic ferromagnetic semiconductors and the Curie point can reach up to at least room temperature in case of the conductive layer obtained at 200 C. It was suggested that in heavily Fe-doped GaAs layers the ferromagnetism is related to the Zener double exchange between Fe atoms with different valence states via an intermediate As and Ga atom.

Published
2019
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9. Magnetic properties, chemical and phase composition of thin manganese silicide films fabricated by pulsed laser deposition

Author

Dorokhin, M. V., Kuznetsov, Yu. M., Lesnikov, V. P., Kudrin, A. V., Erofeeva, I. V., Boryakov, A. V., Kryukov, R. N., Nikolitchev, D. E., Zubkov, S. Yu., Trushin, V. N., and Demina, P. B.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Applied Physics
Abstract

Manganese silicide (MnxSiy) thin films with Mn content (CMn) varied from 24 at. % to 52 at. % were grown on i-GaAs (100) substrates. Chemical, phase composition and room temperature magnetic properties of the films were investigated. It was demonstrated that manganese silicide films revealing ferromagnetic properties are multiphase systems. The phases, which are believed to be non-magnetic at room temperature, are compounds with Mn concentration exceeding the average Mn content of the film (higher manganese silicide, MnSi and Mn5Si3). Magnetic properties revealed are attributed with the secondary phases which are Mn doped silicon (Mn:Si) or Mn depleted compounds. For nearly single phase films (with very small 2-nd phase ratio) no room temperature ferromagnetism was observed.

Published
2018

31. Formation of a Fine-Grained Si1–xGexThermoelectric by Spark Plasma Sintering.

Author

Dorokhin, M. V., Boldin, M. S., Uskova, E. A., Boryakov, A. V., Demina, P. B., Erofeeva, I. V., Zdoroveyshchev, A. V., Kotomina, V. E., Kuznetsov, Yu. M., Lantsev, E. A., Popov, A. A., and Trushin, V. N.

Subjects
DIFFUSION kinetics, SOLID solutions, PLASMA temperature, GRAIN size, SINTERING
Abstract

The kinetics of diffusion processes occurring during the formation of polycrystalline Si1 –xGex nanostructures (x = 0.20, 0.35) by spark plasma sintering in the temperature range 20–1200°C was studied for the first time. A mechanism for the formation of a SiGe solid solution is proposed as a result of a comprehensive study of the microstructure and phase composition of samples with particle sizes from 150 nm to 100 µm, together with the analysis of experimental sintering maps. It is based on the phenomenon of mutual diffusion of Si and Ge atoms that occurs during the entire sintering process. For the selected sintering modes, the grain size of the formed SiGe corresponds to the size of the initial powder particles. [ABSTRACT FROM AUTHOR]

Published
2024
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45. Spray Film-Forming systems as promising topical in situ Systems: A review.

Author

Bakhrushina, Elena O., Shumkova, Marina M., Sergienko, Felix S., Novozhilova, Elizaveta V., and Demina, Natalia B.

Abstract

Spray film-forming systems are applied to the skin as a liquid or semi-solid preparation and, by evaporation of the solvent on the skin, the polymer contained forms a solid film. [Display omitted] Spray film-forming systems (SFFSs) provide great potential for the treatment of various types of wounds. Such systems afford to prolong the action of active substances, to prevent cross-contamination, and to ensure accelerated wound healing. Spray films are known since the mid-20th century, and nowadays they are widely used to treat minor skin injuries, but numerous clinical cases describe their successful use in the treatment of burns, wounds, bedsores, etc. The current level of polymer development and composite synthesis has greatly expanded the possibilities of creating compositions of spray film-forming systems. Scattered information and lack of standardization of such delivery systems creates difficulties for pharmaceutical development. This review highlights most of the existing requirements and suggestions from studies to standardize the characteristics of SFFSs and classify them based on scientific sources and regulatory documentation, as well as the position of such systems in the pharmaceutical market. The search and evaluation of known characterization methods and their modifications, as well as the approval of their list (separately for development and for standardization) can potentially increase the research interest in the problem of spray film-forming systems development and contribute to the registration of new drugs and medical devices in this promising dosage form, including with its own pharmacological effect. [ABSTRACT FROM AUTHOR]

Published
2023
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