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The mechanical properties comprising the stress-strain characteristics under uniaxial tensile deformation, the acoustic properties from mechanical resonance spectroscopy and—in parallel—the microstructural evolution during deformation of a nonequiatomic high-entropy alloy (HEA) Fe50Mn30Co10Cr10 have been studied in a wide temperature range, including ultralow temperatures down to 0.5 K. In the temperature range 300 to 4.2 K, a strong temperature dependence of the tensile strength occurs, hinting at the thermally activated nature of plastic deformation. Within the range of extremely low temperatures (4.2–0.5 K), however, the alloy exhibits anomalies of the yield strength, as well as discontinuous plasticity. Over the whole temperature range, the dynamic Young’s modulus of tensile deformed samples shows a reduction of absolute values compared to those of the undeformed ones, and at temperatures < 30 K a change of the temperature dependence from almost linear to power-law type. At all temperatures down to 0.5 K, the alloy’s plasticity stays as high as 50% as a consequence of a deformation driven martensitic phase transformation from fcc to hcp lattice (TRIP effect). Considering the ultralow deformation temperatures, the tensile strength reaches record values of 1513 MPa at 4.2 K, and still of 1274 MPa at 0.5 K, each being paired with significant strain hardening. These results suggest the HEA Fe50Mn30Co10Cr10 as a promising structural material for use in cryogenic environments down to extremely low temperatures.

Dispersion properties of electromagnetic eigenmodes in a semiconductor nanotube (with quadratic electron dispersion law) filled by a nonmagnetic dielectric and placed in a coaxial dc magnetic field are studied theoretically. A new quantum electrodynamical phenomenon is predicted. Namely, it is shown that increase in the electron density [Formula: see text] in the nanotube results in the appearance of new branches in the eigenmodes spectrum. These branches arise in a bifurcation manner at some critical values of [Formula: see text], when a new electron energy subzone starts to fill in. The number of branches monotonously increases with growth [Formula: see text] and oscillates with increase in the number of magnetic flux quanta through the nanotube (i.e., a peculiar Aharonov–Bohm effect takes place). We also found that the dispersion curves have parts with anomalous dispersion. The analytical expression for electron energy loss due to the excitation of eigenmodes under the Cherenkov resonance condition is derived and numerically analyzed.

This article investigates the magnetic susceptibility, χ(T), of the two-phase (R32 + C2/c) crystal LaCr3(BO3)4 in the temperature range 2–300 K for two orientations of an external magnetic field. It has been established that both structural modifications of lanthanum chromium borate are ordered antiferromagnetically, with each of them having its own Neel temperature (6.5 and 8.5 K). It has been shown that at T > 60 K, the magnetic susceptibility is well described by the Curie–Weiss law with an effective magnetic moment of μeff = 3.86 μB/Cr3+ and a Curie–Weiss temperature of θ = –23 K. Within the Heisenberg spin chain model, taking into account the interchain exchange interaction, the authors have obtained the following exchange-interaction constants: an antiferromagnetic intrachain exchange (J/k = 4.8 K) and a ferromagnetic interchain exchange (J'/k = –0.28 K).

The magnetic characteristics of ensembles of La0.6Sm0.1Sr0.3MnO3 nanoparticles measured at different temperatures are analyzed quantitatively. The field and temperature dependences of the magnetization of the ensemble are calculated on the basis of this analysis. The calculations indicate that the spread in the parameters of the nanoparticles has a decisive influence on the key magnetic parameters of the ensemble: coercitive force, residual magnetization, and blocking temperature. It is shown that complete agreement between the experimental and calculated dependences is possible only if it is assumed that two different regions contribute to the total magnetic signal: anisotropic strong magnetic and isotropic weak magnetic regions. The effect of temperature on the behavior of the two types of regions is determined. It is concluded that the analytic procedure proposed here can be used to characterize the properties of other systems of magnetic nanoparticles, and can also be extended to the analysis and pred...

This study is a comprehensive analysis of a multilayer F1/f(d)/F2pin structure's magnetic resonance properties, wherein F1 and F2pin are the free and exchange-coupled strong magnetic layers, and f is the weakly magnetic layer with a Curie point in the room temperature region. Depending on the magnetic state of the spacer f (ferromagnetic or paramagnetic) the exchange interaction between the F2 and F2pin layers becomes a function of the temperature, which opens up opportunities for practical applications. The obtained results show that the interlayer exchange coupling can be enhanced by decreasing the thickness of the spacer d, or by lowering the temperature. Strengthening the exchange coupling leads to a stronger manifestation of unidirectional anisotropy in the ferromagnetic resonance layer F1, as well as to a broadening of the resonance line that is atypical for thin films. The observed features are analyzed in the context of comparing the effects of two different natures: the influence of the spacer d and the influence of the temperature. Thus, the behavior of changes to the unidirectional anisotropy remains the same given variation of both the thickness of the spacer and the temperature. However the broadening of the magnetic resonance line is more sensitive to changes in the interlayer interaction caused by variation of d, and is less susceptible to changes caused by temperature.

Two series of nanosized cobalt spinel ferrites CoFe2O4 are synthesized from metal salts using high-energy ball milling with the addition of NaCl as a growth agent (series CFO-NaCl), and without (CFO Series). The particle properties are characterized using atomic force microscopy, as well as magnetic and calorimetric measurements. It is shown that the average sizes of the nanoparticles were ∼5.6 and ∼10.3 nm for CFO and CFO-NaCl series, respectively. We performed magnetostatic measurements and determined the parameters that are required to analyze the magnetic state and remagnetization processes of the nanoparticles. It is shown that the blocking temperature is ≈160 K for CFO samples and ≈300 K for the CFO-NaCl series. It was concluded that at 293 K the CFO series particles exhibit a superparamagnetic state, whereas the CFO-NaCl series are in the blocked state. The specific loss power that is scattered by the synthesized nanoparticle ensembles placed in an alternating magnetic field, is measured experiment...

The effect of a magnetic field on the magnetic susceptibility χ(T) and the temperature of the three magnetic phase transitions in single-crystal β-TeVO4 is studied at low temperatures. The H-T phase diagram is obtained for H||b and H ⊥ b. A tricritical point with coordinates H* = 3.2 ± 0.1 T and T* = 3.0 ± 0.1 K is found for H||b.

Frequencies of the surface electromagnetic states in the photonic crystal–ferrite–plasma-like medium structure were studied both theoretically and experimentally as a function of the ferrite layer thickness, external dc magnetic field and temperature. The photonic crystal was a periodic stack of a finite number of unit cells, each consisting of two different nonmagnetic dielectrics. A nonmagnetic semiconductor played the role of a plasma-like medium. A dc magnetic field was applied parallel to the ferrite layer. The propagation direction of an electromagnetic wave was perpendicular to the dc magnetic field with the electrical component of a microwave field parallel to the magnetic field. An analytical expression relating the frequencies of the surface electromagnetic states to the structural parameters and the magnitude of the dc magnetic field value was derived within the framework of the model of non-conducting and magnetized to saturation ferrite. It was predicted that the states under study are multim...

Magnetic properties of single crystal β-TeVO4 with a zigzag chain of magnetic centers (V4+ ions, S = 1/2) are analyzed in the framework of the J1–J2 model. The best agreement with experimental data is obtained for the J1–J2 model with parameters J1/kB = −38.33 K and J2/kB = 29.48 K (gb = 2.07, ga,c = 1.99). In contrast to the previously used model (a uniform antiferromagnetic spin chain system with J1/kB = 21.4 K (gb = 2.28, ga,c = 2.18)), this improved result allows one to consider the object under study as a zigzag chain system with a dominant ferromagnetic exchange between the nearest neighbors and an antiferromagnetic interaction between the next-nearest neighbors.

An analytic approach is developed in the nearest neighbor approximation for describing electron transport through axially symmetric junctions of zigzag and armchair nanotubes. This method yields an analytic expression for the electron transmission probability and can be used to establish selection rules for electron scattering. Oscillations in the gap width in the electron transmission spectrum are predicted as a function of the nanotube diameter and the minimum gap size is determined. The thresholds for the appearance of steps in the electron transmission coefficient are also found and it is shown that, except in its initial section, the origin of the steps is associated with the electronic characteristics of armchair nanotubes, alone.

The current-voltage (I–V) characteristics of a metal–molecule–metal structure are investigated under the condition that electron tunneling occurs only via a single molecular level of arbitrary degeneracy. A system of kinetic equations taking into account the accumulation of charge on the molecule is solved, and an exact formula for the steady-state current is obtained for the first time. In the low-temperature limit the steps on the I–V characteristic are analyzed and found to be nonequidistant with respect to current. It is shown that with increasing degeneracy of the level the initial current steps tend toward a completely equidistant spacing. In the case when the coupling parameters between the molecule and external electrodes are substantially different, the behavior of the I–V curves on parts with opposite directions of the current is found to be different: either a single current step is formed, with an amplitude proportional to the degeneracy of the level, or equidistant current steps appear in a n...