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Your search keyword '"Kourov, N. I."' showing total 40 results
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40 results on '"Kourov, N. I."'

1. Half-Metallic Ferromagnets and Spin Gapless Semiconductors

Author

Marchenkov, V. V., Kourov, N. I., and Irkhin, V. Yu.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

A brief review of experimental and theoretical studies of half-metallic ferromagnets (HMF) and spin gapless semiconductors (SGS) is given. The data on resistivity and magnetoresistivity are presented. An important role of non-quasiparticle states owing to electron-magnon scattering in transport properties is discussed. The problem of low-temperature resistivity in HMF is treated in terms of one-magnon and two-magnon scattering processes., Comment: Physics of Metals and Metallography, special issue, 4 pages

Published
2019
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2. Peculiarities of the electronic transport in half-metallic Co-based Heusler alloys

Author

Marchenkov, V. V., Perevozchikova, Yu. A., Kourov, N. I., Irkhin, V. Yu., Eisterer, M., and Gao, T.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

Electrical, magnetic and galvanomagnetic properties of half-metallic Heusler alloys of Co$_2$YZ (Y = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn, Sb) were studied in the temperature range 4.2--900 K and in magnetic fields of up to 100 kOe. It was found that varying Y in affects strongly the electric resistivity and its temperature dependence $\rho(T)$, while this effect is not observed upon changing Z. When Y is varied, extrema (maximum or minimum) are observed in $\rho(T)$ near the Curie temperature $T_C$. At $T < T_C$, the $\rho(T)$ behavior can be ascribed to a change in electronic energy spectrum near the Fermi level. The coefficients of the normal and anomalous Hall effect were determined. It was shown that the latter coefficient, $R_S$, is related to the residual resistivity $\rho_0$ by a power law $R_S \sim \rho_0^k/M_S$ with $M_S$ the spontaneous magnetization. The exponent $k$ was found to be 1.8 for Co$_2$FeZ alloys, which is typical for asymmetric scattering mechanisms, and 2.9 for Co$_2$YAl alloys, which indicates an additional contribution to the anomalous Hall effect. The temperature dependence of resistivity at low temperatures is analyzed and discussed in the framework of the two-magnon scattering theory., Comment: Invited Report on the Moscow International Symposium on Magnetism MISM-2017, pdf only, 6 pages, J. Magn. Magn. Mater., in press

Published
2017
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30. Magnetic and thermal properties of alloys close in composition to the spin gapless semiconductor Mn2CoAl

Author

Semiannikova, A. A., Kourov, N. I., Korolev, A. V., Perevozchikova, Y. A., Marchenkova, E. B., Korenistov, P. S., Domozhirova, A. N., Marchenkov, V. V., Semiannikova, A. A., Kourov, N. I., Korolev, A. V., Perevozchikova, Y. A., Marchenkova, E. B., Korenistov, P. S., Domozhirova, A. N., and Marchenkov, V. V.

Abstract

The field dependence of magnetization at T = 4.2 K and in magnetic fields of up to 70 kOe, temperature dependences of magnetization (2 K < T < 300 K), heat capacity (2 K < T < 30 K) and magnetic susceptibility (2 K < T < 1000 K) for Mn1.99Co0.96Al1.05 and Mn1.79Co1.25Al0.96 alloys, closed in composition to the Mn2CoAl spin gapless semiconductor, were studied. Alloys studied were demonstrated to be the band ferromagnets. Their high-field (H > 11 kOe) magnetization is described in the Stoner models with the Rhodes-Wohlfarth parameter pRW = 1.3 for Mn1.99Co0.96Al1.05 and pRW = 2.3 for Mn1.79Co1.25Al0.96. When the composition deviates from the stoichiometric Mn2CoAl, the spontaneous moment decreases slightly, the effective moment, on the contrary, increases. In this case, a negative sign of the temperature-independent component of the paramagnetic susceptibility is observed. The density of states n(EF) at Fermi level and the Debye temperature ΘD of studied alloys have the usual values for 3d-metal alloys. © 2021 Author(s).

Published
2021

33. Peculiarities of the electronic transport in half-metallic Co-based Heusler alloys

Author

Marchenkov, V. V., Perevozchikova, Y. A., Kourov, N. I., Irkhin, V. Y., Eisterer, M., Gao, T., Marchenkov, V. V., Perevozchikova, Y. A., Kourov, N. I., Irkhin, V. Y., Eisterer, M., and Gao, T.

Abstract

Electrical, magnetic and galvanomagnetic properties of half-metallic Heusler alloys of Co2YZ (Y = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn, Sb) were studied in the temperature range 4.2–900 K and in magnetic fields of up to 100 kOe. It was found that varying Y in Co2YZ alloys affects strongly the electric resistivity and its temperature dependence ρ(T), while this effect is not observed upon changing Z. When Y is varied, extrema (maximum or minimum) are observed in ρ(T) near the Curie temperature TC. At T ≤ TC, the ρ(T) behavior can be ascribed to a change in electronic energy spectrum near the Fermi level. The coefficients of normal and anomalous Hall effect were determined. It was shown that the latter coefficient, RS, is related to the residual resistivity ρ0 by a power law RS ∼ ρ0 k/MS with MS the spontaneous magnetization. The exponent k was found to be 1.8 for Co2FeZ alloys, which is typical for asymmetric scattering mechanisms, and 2.9 for Co2YAl alloys, which indicates an additional contribution to the anomalous Hall effect. The temperature dependence of resistivity at low temperatures is analyzed and discussed in the frame of the two-magnon scattering theory. © 2017 Elsevier B.V.

Published
2018

38. Thermoelastic Martensite Transformations and the Properties of Ultrafine-Grained Ni54Mn20Fe1Ga25 Alloys Obtained by Melt Quenching.

Author

Marchenkova, E. B., Pushin, V. G., Kazantsev, V. A., Korolev, A. V., Kourov, N. I., and Pushin, A. V.

Abstract

Abstract: Studies of structural and phase transformations in the cast and melt-quenched ferromagnetic four-component alloy Ni54Mn20Fe1Ga25 were performed using transmission and scanning electron microscopy and X-ray diffraction, The obtained data have been compared with the results of studies of physical characteristics (electrical resistance, thermopower, magnetic susceptibility, magnetization, and temperature coefficients of linear expansion and relative elongation ΔL/L measured by the method of dilatometry) in the temperature range of 2-870 K. This work has established the effects of quenching on the microstructure, magnetic state, critical temperatures, and specific features of thermoelastic martensitic transformations in the alloy. [ABSTRACT FROM AUTHOR]

Published
2018
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39. Features of Crystallization of Rapidly Quenched Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 Alloys from Melt with High-Temperature Shape Memory Effect.

Author

Pushin, A. V., Pushin, V. G., Kuntsevich, T. E., Kuranova, N. N., Makarov, V. V., Uksusnikov, A. N., and Kourov, N. I.

Subjects
NICKEL alloys, CRYSTALLIZATION, METAL quenching, SHAPE memory effect, SCANNING electron microscopy
Abstract

A comparative study of the structure and the chemical and phase composition of Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 amorphous alloys obtained by fast-quenching of melt stream by spinning has been carried out by transmission and scanning electron microscopy and X-ray diffraction. The critical temperatures of their devitrification were determined by the data of temperatures measurements of electrical resistance. The features of the formation of ultrafine structure and the phase transformation at the vitrification depending on the regimes of heat treatment and chemical composition of alloy have been established. [ABSTRACT FROM AUTHOR]

Published
2017
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