Vol 124, No 1 (2023)

The temperature behavior of high-frequency magnetoimpedance (MI) in amorphous microwires in a glass sheath has been studied in the temperature range up to the Curie temperature TC. Two alloy samples with compositions of Co27.4Fe5B12.26Si12.26Ni43.08 (TC ≈ 48°C) and Co64.82Fe3.9B10.2Si12Cr9Mo0.08 (TC ≈ 61°C) with different signs of magnetostriction constant λs and with different types of magnetic anisotropy were used. For the first alloy sample, λs < 0, which leads to circular anisotropy. For the second alloy sample, λs > 0, and easy axis anisotropy is formed along the wire axis. A substantial decrease in the impedance is observed at elevated frequencies with an increase in the temperature in microwires with easy axis anisotropy, regardless of the application of a magnetic field, while the change in the impedance in wires with circular anisotropy is more substantial in the presence of an external field. Moreover, the change in the impedance with an increase in the temperature from room temperature to TC can reach 200–300% in the frequency range of 0.5–0.9 GHz in a magnetic field of about 10 Oe. These results may be of interest for the development of miniature temperature sensors.

Sm(Fe,Co,Ti)12-based alloys with low contents of rare-earth elements are promising materials for manufactoring high-energy permanent magnets. The (Sm,Zr)(Fe,Co)10.3Ti0.7 alloy has been produced by strip casting with low quenching rates. The structure and magnetic properties of the alloy were studied by scanning electron microscopy, as well as X-ray and thermomagnetic analysis. The initial inhomogeneous alloy was subjected to solid-solution treatment at 1150°С. The alloy retained a high-anisotropy state typical of the Sm(Fe,Co,Ti)12 phase.

The continual and quantum-mechanical models of magnetic dynamics are considered for a system of ferromagnetic nanoparticles with different forms of magnetic anisotropy alongside with the corresponding theory for describing the Mössbauer spectra of such materials. The calculations of spectra in these models demonstrate various forms of the magnetic hyperfine structure upon the evolution of the absorption spectra of nanoparticles from a well-resolved magnetic hyperfine structure (sextet of lines for 57Fe nuclei) at low tem-peratures to a single line or a five-stage pedestal at high temperatures. These models substantially broaden the methodological basis for the diagnostics of magnetic nanomaterials by the method of Mössbauer spec-troscopy.

This paper presents a theoretical study of the dynamics of the induced magnetization and spin cur-rent arising in a layer of an impure superconductor due to the proximity to a ferromagnetic dielectric with a uniform periodically precessing magnetization. The dynamics of the observed physical quantities is described within the semi-classical Usadel–Floquet formalism, which makes it possible to study the effect of a periodic perturbation on an inhomogeneous superconducting system. The spatial distributions and temporal evolu-tion of the induced magnetization and the superconducting spin current inside the superconductor layer are found from the numerical solutions of the system of Usadel–Floquet equations.

The R(T) dependences of thin superconducting aluminum films deposited on leucosapphire and gallium arsenide substrates by electron beam sputtering and molecular beam epitaxy have been experimen-tally studied. Regardless of morphology, a noticeable increase in the critical temperature of the supercon-ducting transition with a decrease in the film thickness is found. The effect is interpreted as a manifestation of the quantum size effect.

X-ray diffraction analysis and optical and electron microscopy have been used to study the effect of mechanical activation conditions of the Cu–12% Sn mixture with different Cu9Al4 modifier contents on the structure and phase composition and morphology of formed composites. The mechanochemical intro-duction of 10 wt % of the modifying additive into the matrix of mechanically synthesized tin bronze mainly results in the formation of a ternary Al0.05Cu0.9Sn0.05 solid solution of aluminum and tin in copper. In the case of the 20 wt % modifying additive, the final product contains a Cu0.9Sn0.1 tin solid solution in copper and Cu9Al4 intermetallics. Studies of the mechanical and tribological characteristics of the material prepared by sintering under a pressure showed that the intensity of wear of the material based on the Cu–12 wt % Sn mechanochemically synthesized bronze is insignificant lower than that of commercial bronze alloy CuSn10P; the coefficient of friction (f) decreases by ~1.3 times and the range of its values is sufficiently wide,
f = 0.7–0.9. The modification of the Cu–12 wt % Sn mechanically synthesized bronze with the Cu9Al4 inter-metallics allowed us to decrease the intensity of wear by 1.3 to 1.6 times and to substantially decrease the coef-ficient of friction (by 1.2 to 1.6 times). The stable value f = 0.5 is reached for the mechanically activated
Cu‒12 wt % Sn + 20 wt % Cu9Al4 composition. The introduction of the intermetallics results in the increase in the microhardness of the alloys by 1.6 to 2 times (to Hμ = 2730 MPa) compared to those of CuSn10P and mechanically synthesized bronzes.

IR spectroscopy, electron microscopy, and X-ray diffraction analysis, including the application of synchrotron radiation, have been used to study the mechanochemical reduction of copper oxide with alumi-num at the stoichiometric ratio of the components and in the presence of an excess of oxide-forming metal and aluminum solid solution in copper as well. The possibility is shown of the mechanochemical reduction of copper oxide with aluminum and aluminum solid solution in copper, which is accompanied by the forma-
tion of the Сu/Al2O3 composite structure. To modify copper with alumina, using an aluminum solid solution in copper is preferable.

The microstructural evolution of the ordered Cu–56 at % Au alloy under plastic deformation has been studied. It has been revealed that under the influence of deformation, the с-domain structure is origi-nally destroyed, and the lamellar structure demonstrates a higher stability under deformation impacts. It has been demonstrated that deformation to 70% leads to the formation of ultrafine-grained two-phase (order + disorder) structure in the alloy. Based on the results of mechanical tensile tests, the deformation behavior of the ordered and disordered alloys has been analyzed. It has been concluded that the mechanical properties of the moderately deformed (to ~20%) ordered Cu–56 at % Au alloy may be of interest for practical appli-cations.

Scanning and transmission electron microscopy has been used to investigate the nickel structure formed by high pressure torsion deformation at temperatures of 100–250°C. The relationship between the structure and temperature–rate conditions of deformation, which is characterized by the Zener–Hollomon parameter (Z), has been found. A change in the temperature–rate conditions of deformation has been shown to alter the dominant structure-forming process and to change the resultant structure. We have identified lnZ ranges where these processes occurred, namely, dynamic recovery at lnZ > 25, dynamic recrystallization at 21 < lnZ < 25, and dynamic polygonization at lnZ < 21.