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Your search keyword '"Shakhov, M. A."' showing total 122 results
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122 results on '"Shakhov, M. A."'

2. High temperature magnetism and microstructure of semiconducting ferromagnetic alloy (GaSb)$_{1-x}$(MnSb)$_{x}$

Author

Oveshnikov, L. N., Nekhaeva, E. I., Kochura, A. V., Davydov, A. B., Shakhov, M. A., Marenkin, S. F., Novodvorskii, O. A., Kuzmenko, A. P., Vasiliev, A. L., Aronzon, B. A., and Lahderanta, E.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

We have studied the properties of relatively thick (about 120 nm) magnetic composite films grown by pulsed laser deposition method using (GaSb)$_{0.59}$(MnSb)$_{0.41}$ eutectic compound as a target for sputtering. For the studied films we have observed ferromagnetism and anomalous Hall effect above the room temperature, it manifests the presence of spin-polarized carriers. Electron microscopy, atomic and magnetic force microscopy results suggests that films under study have homogenous columnar structure in the bulk while MnSb inclusions accumulate near it's surface. This is in good agreement with high mobility values of charge carriers. Based on our data we conclude that room temperature magnetic and magnetotransport properties of the films are defined by MnSb inclusions., Comment: 7 pages, 6 figures (total of 19 panels)

Published
2018

5. Magnetophonon resonance in quantum wells in tilted field. What is concealed behind its angular dependence?

Author

Afonin, V. V., Gurevich, V. L., Laiho, R., Safonchik, M. O., Shakhov, M. A., and Shubnikov, M. L.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

Magnetophonon resonance in quantum wells in a tilted magnetic field B is investigated. Measurements of the Hall coefficient and correspondingly of the carrier concentration as a functions of magnetic field and temperature are simultaneously performed. It is shown that the experimental data can be interpreted in terms of a great sensitivity of the effect to the variation of the two dimensional carrier concentration n in a certain concentration interval. In other words, the observed angular dependence of the MPR amplitudes is a manifestation of dependence of n on the magnitude of the magnetic field B., Comment: 14 pages, 6 figures

Published
2002

15. Superconducting properties of films deposited from micro-, nanocrystalline and optimally BZO-doped YBCO targets

Author

Huhtinen, H., Peyrla, M., Shakhov, M. A., Laiho, R., Stepanov, Yu. P., Palai, R., Paturi, P., and Raittila, J.

Subjects
Dielectric films -- Electric properties, Thin films -- Electric properties, Magnetic fields -- Measurement, Epitaxy -- Research, Business, Electronics, Electronics and electrical industries
Abstract

The study explains the superconducting properties of films that are deposited from micro-, nanocrystalline and optimally BaZr[O.sub.3] (BZO)-doped Y[Ba.sub.2][Cu.sub.3][O.sub.6X] (YBCO) targets. The doping is found to highly improve the properties of these films.

Published
2007

17. Low-temperature quantum magnetotransport of graphene on SiC (0 0 0 1) in pulsed magnetic fields up to 30 T

Author

Lähderanta, Erkki, Lebedev, A. A., Shakhov, M. A., Stamov, V. N., Lisunov, K. G., Lebedev, S. P., Lappeenrannan-Lahden teknillinen yliopisto LUT, Lappeenranta-Lahti University of Technology LUT, and fi=School of Engineering Science|en=School of Engineering Science

Abstract

Resistivity, ρ(T), and magnetoresistance (MR) are investigated in graphene grown on SiC (0 0 0 1), at temperatures between T ~ 4–85 K in pulsed magnetic fields of B up to 30 T. According to the Raman spectroscopy and Kelvin-probe microscopy data, the material is a single-layer graphene containing ~20% double-layer islands with a submicron scale and relatively high amount of intrinsic defects. The dependence of ρ(T) exhibits a minimum at temperature T m ~ 30 K. The low-field Hall data have yielded a high electron concentration, n R ≈ 1.4 × 1013 cm−2 connected to intrinsic defects, and a mobility value of µ H ~ 300 cm2 (Vs)−1 weakly depending on T. Analysis of the Shubnikov–de Haas oscillations of MR, observed between B ~ 10–30 T, permitted to establish existence of the Berry phase β ≈ 0.55 and the cyclotron mass, m c ≈ 0.07 (in units of the free electron mass) close to expected values for the single-layer graphene, respectively. MR at 4.2 K is negative up to B ~ 9 T, exhibiting a minimum near 3 T. Analysis of MR within the whole range of B = 0–10 T below the onset of the SdH effect has revealed three contributions, connected to (i) the classical MR effect, (ii) the weak localization, and (iii) the electron–electron interaction. Analysis of the ρ(T) dependence has confirmed the presence of the contributions (ii) and (iii), revealing a high importance of the electron–electron scattering. As a result, characteristic relaxation times were obtained; an important role of the spin–orbit interaction in the material has been demonstrated, too. Post-print / Final draft

Published
2019

19. Influence of scattering and interference effects on the low-temperature magnetotransport of Cu2ZnSnS4 single crystals.

Author

Lähderanta, E., Guc, M., Shakhov, M. A., Arushanov, E., and Lisunov, K. G.

Subjects
MAGNETORESISTANCE, SINGLE crystals, TEMPERATURE, METAL-insulator transitions, MAGNETIC fields
Abstract

Activated resistivity, ρ(T), and positive magnetoresistance (MR) are observed in Cu2ZnSnS4 single crystals within the temperature interval between T ∼ 2 and 300K in pulsed magnetic fields of B up to 20 T. Between T ∼ 50 and 150 K, the charge transfer is described by the Mott variable-range hopping (VRH) transport over localized states of the defect acceptor band with width W ∼ 12-25 meV. Up to the highest applied fields, MR follows the law ln ρ(B) ∞ B² pertinent to the VRH conduction at λ ⪢ a, where λ is the magnetic length and a is the localization radius. The joint analysis of the MR and ρ(T) data yielded a series of microscopic parameters, including the values of a ≈ 22-45 Å, depending on the proximity of a sample to the metal-insulator transition. However, below T ∼ 3-4K the Shklovskii-Efros VRH conduction is observed. Here, the behavior of MR changes drastically, exhibiting a sharp contraction of the quadratic MR region and transformation of the MR law into those of ln ρ (B) ∞ B2/3 or / B3/4 when B is increased. In addition, such behavior of MR is accompanied by a dramatic increase of the localization radius a ≈ 50-170 Å. Both anomalies above are explained quantitatively by the same reason, connected to the constructive interference of different paths arising from multiple scattering of hopping carriers at low temperatures. In particular, the low-temperature values of the localization radius, evaluated in frames of the theory of interference phenomena in the VRH conduction, exhibit a reasonable agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Published
2016
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26. Influence of BaZrO3 dopant concentration on properties of YBa2Cu3O6+x films in magnetic fields up to 30 T.

Author

Huhtinen, H., Irjala, M., Paturi, P., Shakhov, M. A., and Laiho, R.

Subjects
SEMICONDUCTOR doping, BARIUM compounds, ZIRCONIUM compounds, THIN film research, FLUX pinning, MAGNETIC properties of superconductors, MAGNETIC fields
Abstract

The effect of BaZrO3 (BZO) dopant concentration on superconducting properties in YBa2Cu3O6+x thin films is investigated in a wide magnetic field range up to 30 T. Based on the magnetization and resistivity measurements, the optimal BZO concentration for flux pinning is found to be 4% up to 20 T and increasing up to around 8% in higher fields. This result is qualitatively explained by a model where more BZO is needed in order to organize optimal columnar defect structure at high fields because the amount of single BZO particles acting as isotropic point pinning centers is increased, especially in high BZO concentrations. This means that for applications of thin film or coated conductor structures carried out at high magnetic fields, even higher dopant concentration than used in a low-field range should be produced in order to attain the optimal flux pinning conditions. [ABSTRACT FROM AUTHOR]

Published
2010
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30. Variable-range hopping conductivity and absence of a true metal–insulator transition in La[sub 0.7-δ] Ca[sub 0.3]Mn[sub 1-y]Fe[sub y]O[sub 3].

Author

Laiho, R., La¨hderanta, E., Salminen, J., Lisunov, K. G., Zakhvalinskii, V. S., Safontchik, M. O., Shakhov, M. A., and Shubnikov, M. L.

Subjects
HOPPING conduction, METALS
Abstract

Resistivity of La[sub 0.7-δ]Ca[sub 0.3]Mn[sub 1-y]Fe[sub y]O[sub 3] (LCMFO) with y = 0-0.05, δ = 0 and 0.017 is investigated between 4.2-350 K, showing that La vacancies increase the effect of Fe doping by influencing electronic states through additional microscope disorder. The Shklovskii-Efros variable-range hopping conductivity, governed by generation of a soft parabolic gap in the spectrum of localized states due to Coulomb interaction between charge carriers, is observed both above and well below the ferromagnetic-to-paramagnetic transition temperature. Our results give evidence for absence of a true metal-insulator transition both in undoped material and in LCMFO. [ABSTRACT FROM AUTHOR]

Published
2002
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35. Large magnetoresistance effect in InN epilayers

Author

Komissarova, T. A., primary, Shakhov, M. A., additional, Jmerik, V. N., additional, Parfeniev, R. V., additional, Paturi, P., additional, Wang, X., additional, Yoshikawa, A., additional, and Ivanov, S. V., additional

Published
2010
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