Vol 61, No 8 (2018)

The paper examines the characteristics of the miniature sensor of weak magnetic fields on the resonant microstrip structure with a thin ferromagnetic film. The authors calculated the frequency response of irregular microstrip resonator containing anisotropic magnetic film in quasi-static approximation. The resonator is connected to transmission lines via coupling capacities. The authors determined the optimal directional angles of the constant magnetic displacement field ensuring maximum sensitivity of the sensor. They examined the impact of angular and amplitude dispersion of uniaxial magnetic anisotropy of thin film upon the sensor characteristics. The regularities determined in this research qualitatively agree with the experimental results.

Consequences of the non-Hermitian expansion of the Dirac equation in which the mass term is written in the form m → m₁ + γ₅m₂ are considered. It is shown that such procedure inevitably leads to violation of the weak equivalence principle, i.e., causes an inequality of gravitational and inert fermion masses. However, if to relate the Hermitian, m₁, and non-Hermitian, m₂, masses by the additional condition m₂/m₁ = m₁/2M ≤ 1, the possibility arises to preserve the equivalence principle for fermions of the standard model with high accuracy. In this case, the parameter M = const is the universal constant with dimensionality of mass that can be related to a maximum possible allowed fermion mass in this model. As a consequence of the same condition, a new class of solutions of the modified Dirac equation arises that describes particles whose properties make them obvious candidates for dark matter.

Exact solutions are obtained for models of general scalar-tensor gravitational theories admitting the existence of privileged coordinate systems in which the eikonal equation can be integrated by the method of complete separation of variables of (2.1) type. Characteristics of radiation and explicit forms of functions of the scalar field entering into the field equations of generalized scalar-tensor gravitational theory are obtained.

Evolution of the parametric q-entropy and the q-information difference is considered during transition from a laminar to turbulent flow for nonextensive self-organizing systems. The S- and I-theorems on changes of measures under the Gibbs condition of mean energy constancy are proved.

The method of modulation polarimetry used for measuring bearing and roll angles of a moving object (MO) is investigated for the general case of a radio beacon transmitting orthogonally elliptically polarized signals from two spatially spaced points. Resultant vector signals of the radio beacon are received by the antenna of an onboard single-channel radio receiving device in the path of which a polarization modulator is inserted. The bearing and roll angles are estimated at the output from the receiver at the frequency multiple to the frequency of polarization modulation of the resultant signals received by the radio beacon.

Electrical and magnetic properties of the semimagnetic semiconductor Hg_1–x–yMn_xFe_yTe_1–zS_z solid solutions were studied in the ranges of temperatures 77–320 K and magnetic fields 0.25–6 kOe. In the crystals under study, the effect of giant magnetoresistance was observed that reached 75% at low temperatures. This is due to the fact that charge carriers that participate in the current transfer interact with a magnetized ferromagnetic cluster subsystem (Fe–Fe–Fe) and become spin-polarized. It is these spin-polarized charge carriers that are strongly scattered on antiferromagnetic Mn–S–Mn–S and Mn–Te–Mn–Te clusters, since the magnetic moments inside the clusters and the resulting magnetic moments of these clusters are randomly oriented.

Experimental data on studying ohmic contacts based on single-layer and multilayer metallizations on GaN and (In, Al, Ga)N solid solutions are analyzed. The contact resistance of the Ti/Al/Mo/Au and Ti/Al/Mo/W/Au metallizations on undoped GaN is studied. The dependences of the contact resistance on the GaN surface treatment before the metallization and on the metallization annealing regimes are investigated.

An experimental-computational method of non-stationary thermal diagnostics and non-destructive testing of metallic and non-metallic sheaths and plates, including their inner surfaces inaccessible for direct inspection, by analyzing a non-stationary temperature field generated by the point dynamic heating of the outer surface of the sheath and registered by a thermal imaging device is described.

Results of investigations of the two-way shape memory effect (TWSME) and its stability during stress-free thermal cycling of [001]-oriented Ni₄₉Fe₁₈Ga₂₇Co₆ single crystals after high-temperature isothermal training (100 loading/unloading cycles at a temperature of 373 K) in superelasticity (SE) conditions during L2₁–L1₀ martensitic transformations (MT) are presented. A maximal reversible strain of single crystals aged at 673 K for 4 h with 3.8% TWSME has been obtained. For crystals after stress-free aging at 673 K for 4 h, the TWSME is 2.2%. It has been established that on the one hand, the high-temperature training at 373 K, in comparison with analogous training at a low temperature of 295 K of stress-assisted aged crystals causes the maximal TWSME to decrease by 1.7%, and on the other hand, it promotes the increase of the cyclic stability of TWSME during reversible strain. The influence of the isothermal training temperature on the TWSME mechanism and on its degradation during stress-free cooling/heating cycles is discussed.

The paper presents research into the surface morphology, helium cluster formation and mechanical properties of high-purity tungsten after the high fluence and low-energy helium ion implantation and subsequent annealing. Investigations are based on scanning electron and atomic force microscopy observations and thermal desorption measurements. Because of the local stresses appearing within the energy loss straggling of helium ions, atoms migrate at distances significantly increasing the ion projective range, and create mobile coalescence of helium atoms and immobile helium-vacancy clusters. The latter form helium bubbles in the energy loss straggling which cause the surface blistering. Local stresses induced by helium coalescence and helium-vacancy clusters beyond the energy loss straggling result in the material strengthening or hardness increase. Subsequent 600°С annealing provides the size growth of blisters on the metal surface irradiated with helium ions and high helium desorption due to the migration of mobile coalescence of helium atoms. With the increasing annealing temperature from 600 to 1000°С, the layer corresponding to the projective range of helium ions fully fractures due to the interstitial helium atoms releasing from immobile helium-vacancy clusters. After 1000°С annealing, the tungsten hardness returns to its initial value.

The paper presents the radiation and thermal treatment of zirconium ceramics with high-energy Al ion beams generated at an accelerating voltage of 1.5 kV, which modifies the structure and electrophysical properties of zirconium ceramics. Compact powder and ceramic samples are used for the radiation and thermal treatment performed at 1123–1173 K. The surface treatment of compact powders leads to the increase in the grain size, whereas the surface of ceramic samples turns black and electrically conductive in depth. This is because the change in the oxygen stoichiometry of zirconium ceramics. Air annealing of treated ceramics returns the sample to the initial state. The phase composition, microhardness and density of ceramic samples display no changes after the radiation and thermal treatment. Under the experimental conditions, the diffusion of aluminum ions in the surface layer is not observed. It is found that the ion beam treatment leads to the decrease in aluminum-containing impurity in the surface layers of zirconium ceramics.

The paper studies the absorption spectrum and the integrated absorption coefficient of organosilicic KO-859 enamel samples modified by silicon dioxide nanoparticles and exposed to solar radiation. It is shown that nanomodification improves the radiation resistance of thermal control coatings and provides stability of their optical properties.

Using the capabilities of the CRYSTAL14 code, the parameters of an equilibrium crystal lattice are obtained and the electronic and vibrational structures of a new chalcopyrite-like Zn₂SeTe crystal are studied. The energy band structure, long-wave vibrational frequencies at the point Г, and elastic moduli are calculated. The dependence of the contributions from the vibrations of individual atoms to the vibrational modes of a crystal caused by filling the cationic or anionic sublattices in the chalcopyrite structure is established.

The results of an experimental investigation performed in this study allow supposing that a change in the aggregate state (crystallization) of a substance on the surface of the introduced small-sized (nano- or submicron) particles significantly affects the grain size in the final states of the alloys and composites. This is due to the fact that the melt – particle system is found in a low-stability state, hence even weak thermal actions of the inoculators-microparticles can influence the final state of the alloy, both its structure and physical-mechanical properties. As a result of thermal interaction between the particle and the melt, whose temperature is close to that of the change of the aggregate state (crystallization), the metal on the surface of the particle changes its aggregate state. A thermal model of the change of the aggregate state of a substance proposed in this study makes it possible to predict the velocity and degree of local cooling of the melt, the crystallization time, and the minimal size of the resulting crystallites as a function of the particle dispersion and mass concentration. The smaller the size of the particles and the higher their mass concentration, the smaller the grain size in the final alloy. The full-scale experiment verified the principles obtained in the thermal model: the smaller the size of introduced particles, the smaller the grain size of the final alloy. The average grain size of the initial technical-grade aluminum was ~1200 μm. Upon introduction of 0.2 wt.% of composite SHS-master alloys of the Al–Ti–B₄C system (average particle size 0.4 μm) the average grain size of the alloy was found to be 410 μm. Upon introduction of 0.2 wt.% of composite SHS-master alloys of the Al–Ti–B system (average particle size 0.7 μm) the average grain size of the alloy was found to be 540 μm.

Results of studying the optical and electrical characteristics of single- and two-layer polymer OLED structures with different thicknesses of radiating layers are presented. It is shown that the efficiency of the OLED structures with thick layers reaches 6.9 cd/A, while similar thin-layer structures have the efficiency 10 times smaller. An increase in the thickness of the radiating layer of the polymer as well as incorporation of additional electron transport layer leads to a decrease in the leakage current and an increase in the efficiency; however, it changes the electroluminescence spectrum of the device.

The last paragraph of the article should read “This work is performed with financial support of the Ministry of Education and Science of the Russian Federation within the framework of the federal target program “Research and development in priority areas of development of the scientific and technological complex of Russia for 2014-2020”, Unique identifier of the work (project) RFMEFI57717X0266.”