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Vol 87, No 11 (2023)
Articles
Neutron facilities of the compact neutron source DARIA: parameters and features
Abstract
The compact neutron source DARIA based on a linear proton accelerator is designed to create neutron beams for a diffractometer, a reflectometer, and a small-angle scattering setup. The experimental setups are optimized in terms of the range of momentum transfer, instrumental resolution, geometric dimensions, as well as in terms of the repetition rate and duration of neutron pulses.
1526-1533
Methods to increase the threshold pulsed magnetic field which causes destruction of a steel inductor under repeated impact
Abstract
Methods of increasing the pulsed magnetic field with an amplitude of about 40 T, which the cylindrical thick-walled inductor made of 30ХГСА steel can withstand without destruction under repeated impact, are considered. The methods include changing the material parameters, magnetic pulse characteristics, inner radius, creating a profile of resistivity decreasing from the inner surface deep into the material.
1534-1540
Capillary constant and surface tension of isobutane–hydrogen solution in temperature range of 298–348 K
Abstract
We presented the results of measuring of the capillary constant of isobutane–hydrogen solution in the temperature range of 298.15–348.15 K at pressures from the saturation pressure of pure isobutane up to 4 MPa. The surface tension of the solution was determined. The equations approximating the concentration and pressure dependences of the capillary constant and surface tension are constructed.
1541-1546
Investigation of semiconductor materials by the thermo-optical method in a magnetic field
Abstract
The results of studying the effect of temperature and magnetic field on the relaxation of the thermo-optical signal in semiconductor samples with different electronic spectra n-Ge, n-InSb, ZnSe:Ni are presented. The results were obtained using a two-beam fiber-optic “pump–probe” method with a Fabry–Perot interferometer in the temperature range from 4.2 to 300 K with the application of a magnetic field up to 8 T. The significant change of behavior of reflected probing beam with wavelength of 1530 nm was found after the action of a pump pulse for the sample of n-Ge at temperatures below 30 K and a field induction of more than 2 T. This phenomenon is caused by transformation of electronic structure.
1547-1553
Thermodynamic crisis during spontaneous boiling-up of superheated n-pentane in a vertical glass tube
Abstract
The kinetics of boiling-up of superheated n-pentane in a glass tube was studied by high-speed video and fast acting pressure sensor. The top of the tube is sealed. It is shown that, as the threshold temperature is approached, the boiling-up of a superheated liquid is accompanied by significant pressure jumps and oscillations, and the formation of a vapor film can begin with self-organization in the near-wall layer of the liquid.
1554-1561
Shear strength of Al–Cu alloy with different types of hardening precipitates: molecular dynamics and continuum modeling
Abstract
A molecular dynamics study of the motion of dislocations in aluminum containing hardening copper precipitates is carried out. The paper considers the interaction of dislocation with four types of precipitates, the structure of which was determined in experimental work. The energy of dislocation segments attached to hardening phases is determined and used as a parameter of the continuum model of the dislocation-precipitate interaction. An increase in energy is observed for hybrid precipitates compared to non-hybrid ones.
1562-1568
Ising nematic in J1–J2 square-lattice Heisenberg model within self-consistent spin-wave theory
Abstract
We study the Ising nematic ordering, the Ising nematic phase transition, and the temperature behavior of the short-range order parameters in spin 1/2 quantum Heisenberg model on two-dimensional square-lattice with exchange parameters of nearest and next-nearest neighbors. Two versions of the self-consistent spin-wave theory with and without auxiliary pseudofermions are considered.
1569-1573
Features of the crystal structure of 2D honeycomb frustrated magnet Li2Ni2TeO6
Abstract
Using neutron powder diffraction at a temperature of 35 K, slightly above the Neel temperature, the features of the crystal structure of two samples of layered honeycomb oxides of the same stoichiometric composition Li2Ni2TeO6 synthesized from precursors, Na2Ni2TeO6 and K2Ni2TeO6, were determined. They have a similar crystal structure, hexagonal space group P63/mcm, structure type P2, but there is a significant difference in the distances between the layers. Both Li2Ni2TeO6 samples crystallize into the orthorhombic space group Cmca, with minor differences in the unit lattice parameters. If Li2Ni2TeO6 from the potassium precursor is single-phase, then the compound from the sodium precursor contains 16 wt % of an additional phase with the same Li2Ni2TeO6 stoichiometry, but more deformed with monoclinic distortions described by the С2/m space group.
1574-1579
Dielectric and optical properties of gas hydrates and ice: ab initio simulation results
Abstract
The dielectric tensors εik(ω), optical absorption spectra R(ω), reflection spectra a(ω) and the density of electronic states N(E) have been calculated for the lattices of gas hydrates with the structure sI and sH, as well as for ice Ih and III. The dependence of the dielectric permittivity on the type of guest molecules in the sI hydrate is considered.
1580-1585
Ab initio calculations of the magnetic anisotropy of Fe/Pt/Fe heterostructures with surface relaxation included
Abstract
A numerical study of the effect of surface relaxation, the equilibrium change in the interplanar distance, on the values of the magnetic and energy characteristics of the Fe/Pt/Fe system was carried out. The contribution of the spin-orbit interaction to the value of the magnetic anisotropy energy is studied as a function of the thickness of the ferromagnetic film.
1586-1592
High hydrostatic pressure and uniaxial compression as factors of overcoming hardseededness in licorice
Abstract
In laboratory experiments, when assessing the effects of exposure to licorice seeds of high hydrostatic pressure and uniaxial compression of these seeds, the effect of overcoming hardseededness was established, which was confirmed by high values of the proportion of normally germinated seeds from the total number of hard seeds in the sample under study. The strength of the seed coat determines the maximum force before the destruction of the seed under uniaxial compression.
1593-1599
Study of electrochemical etching surface of ultrafine-grained nickel using scanning tunneling microscopy
Abstract
An approach that allows a qualitative and quantitative analysis of the grain structure of ultrafine grained nickel by electrochemical etching surface is proposed. The data on the etching relief of ultrafine grained nickel obtained by scanning tunneling microscopy have been analyzed. The bimodality of the structure was revealed, which was confirmed by statistical analysis.
1600-1606
Glass formation processes in fullerene mixtures
Abstract
The local structural features of the A20B80 fullerene mixture (where A = C60 and B = C70) are studied by the molecular dynamics simulations for a wide temperature range, including the phase of an equilibrium liquid phase and a supercooled melt, in order to elucidate the mechanism of formation of the icosahedral short-range order in binary molecular liquids. Structural and cluster analyzes revealed the presence of icosahedral clusters in the supercooled melt phase and determined the critical glass transition temperature.
1607-1612
Optical pumping of rubidium isotopes by Cr3+:BeAl2O4 laser radiation
Abstract
We consider the use of a Cr3+:BeAl2O4 laser in free-running operating as a source of emission for optical pumping rubidium alkali metal vapors. The use of dispersive elements in the composition of the laser cavity makes it possible to smoothly tune lasing wavelength and to realize generation at wavelengths corresponding to the D1 and D2 lines of the 85Rb and 87Rb isotopes. Optical pumping of rubidium isotopes by laser emission with wavelengths of 795 and 780 nm, respectively, is experimentally implemented, and their fluorescence is demonstrated. The question of using a wavelength-tunable laser in the method of spin-exchange optical pumping of noble gases is discussed.
1614-1618
Simulation of noble metal nanocluster systems formation during deposition from a colloid solution
Abstract
A model was proposed for the convective flow of the liquid phase of a colloidal solution of glycerol and noble metal nanoparticles (Ag, Au, Ag/Au) near the substrate. The diffusion approximation is used to describe the formation of nanocluster systems on a substrate. The diffusion-limited aggregation model was implemented by applying a cellular automaton in the Neumann neighborhood. A diverse structure of model systems of nanoclusters, which adequately describes the structural features of the experimental samples, was obtained by varying the aggregation probability parameter. The proposed models can be useful for calibrating the parameters of the experimental production of systems of noble metal nanoclusters, as well as describing in the first approximation the processes that have a decisive effect on nanocluster structures.
1619-1625
Study of the microhardness distribution in a coating based on tungsten carbides obtained by laser surfacing on a stainless steel surface
Abstract
We studied the microhardness of the wear-resistant coating obtained by laser powder surfacing on the surface of 420 stainless steel. The dependences between the treatment mode, the obtained hardness and the geometry of the coating are established. It is determined that when a total equal voltage is applied to all diodes, the generated radiation does not provide uniform penetration of the substrate, and as a result, the formation of a uniform coating, both from the point of view of geometry and from the point of view of overall surface hardness. The hardness values of both individual solid particles of tungsten carbides and the total surface of the zone of thermal influence are obtained.
1626-1630
Fluorescent ratiometric thermometers based on dyads of tetraphenyl porphyrin and zinc-metallated tetraphenyl porphyrin
Abstract
Porphyrins and their derivatives are known for their ability to emit two fluorescence bands. We presented the results of the investigation of the intensity ratio dependence for these bands on temperature in the range of 25–75°C for non-metaled and metal-plated with zinc porphyrins, as well as porphyrin dyads in solutions of 1,2-dichloroethane. A comparative analysis of thermometric parameters of these molecules was carried out.
1631-1636
Investigation of electrophysical and mechanical parameters of piezoceramic materials for cartridge-type deformable mirrors
Abstract
We investigated electrophysical and mechanical parameters of the piezoceramic materials based on lead zirconate titanate. In correspondence with obtained data, modules with multilayer actuators with cross-section area of 4 × 4 mm, nominal displacement up to 4.3 µm and capacitance of the element with 12 nF for cartridge-type deformable mirror were produced.
1637-1641
The non-Wiener dynamics of an ensemble of identical anharmonic oscillators
Abstract
The model of an ensemble of anharmonic oscillators in the field of a common broadband photon-free thermostat is reduced to a model of an ensemble of identical N-level particles in terms of the algebraic perturbation theory. In one region the model describes the Dicke superadiance, and in the other one—oscillating dependence of the collective radiation intensity on the number of the ensemble oscillator. The collective radiation proves to be suppressed with a certain number of oscillators.
1642-1651
Magnetic energy of interaction between a synthetic antiferromagnet and a free layer of a spin-tunnel element
Abstract
An exact expression is found for the magnetostatic energy of interaction of a synthetic antiferromagnet with a free layer of a spin-tunnel element, the ferromagnetic layers of which have the shape of strongly oblate ellipsoids of revolution. It has been established that the exact value of this interaction energy can differ significantly from the usual value, which is calculated using the expression for the demagnetizing field. The parameters are calculated for which the complete compensation of the magnetic interaction of a synthetic antiferromagnet occurs.
1653-1657
Features of magnetic ponderomotive interaction of magnetized to saturation profiled magnetic films
Abstract
We calculated the force of magnetic ponderomotive interaction between two micromagnetic films having a corrugated semi-cylindrical surface represented as a lattice of half magnets in the form of long cylindrical rods. It is found that the lattice interaction force is substantially determined by the distance between the half-cylinders and, depending on this parameter, can manifest itself as an attraction or repulsion force.
1658-1661
Evolution of the domain structure in a FeNiCo nanowire under the action of a magnetic field
Abstract
Based on the experimentally discovered domain structure and its evolution in an external magnetic field in thin films of FeNiCo composition with uniaxial anisotropy, a theoretical model of the magnetization distribution is proposed. The analytical dependence of the domain size on the magnitude of the magnetic field is obtained. The change in magnetoresistance because of the evolution of the magnetic domain structure is calculated.
1662-1666
Some features of electrostatics of uncharged thin-walled cylindrical and conical conductors
Abstract
It is shown that for thin-walled uncharged cylindrical and conical conductors in the field of a point charge, there is an electrostatic “repulsion effect” previously predicted for conductors with a non-through cavity. Axial symmetry of the cavity is not necessary for the manifestation of the effect. This proves the possibility of a “repulsion effect” for conductors with different types of cavities.
1667-1673
Modification of the local structure and properties of zinc-substituted hexagonal barium ferrites for microwave devices under magnetic pulsed processing
Abstract
The results of studies of the effect of magnetic pulse treatment on the local structure and magnetic properties of substituted ferrite for microwave devices are presented. The change in the magnetic properties of ferrites as a result of exposure to them by pulses of a weak magnetic field indicates the possibility of controlling the parameters of ferrites by means of a magnetic field and thereby influence the resonant characteristics of microwave devices based on them.
1674-1676