bluuebunny/crossref_metadata_2025 huggingface dataset:
Multifractal properties of the molybdenum ribbon surface at mechanical loading
Authors: Obidov B. A.  , Korsukov V. E.  , Hilarov V. L.  , Ankudinov A. V.  , Butenko P. N.  , Knyazev S. A.  , Korsukova M. M.
Published: January 2023

The effect of uniaxial tensile stress on the atomic structure and relief of the subsurface layer of molybdenum ribbons has been studied. The destruction of the Mo (100) face with the formation of crystallites was revealed near the crack tip. At the same time, the block structures are found to rotate both in the lateral plane and in its perpendicular plane. The surface layer structure in the lateral plane of the ribbon is fragmented into sections, which is associated with the surface relief at different scales. With a help of the concept of multifractal formalism, the spectra of singularities of the initial, loaded and ruptured surface are calculated. It is found that the width of the singularity spectrum, can serve as an indication of the forthcoming rupture.. Keywords: molybdenum ribbon, mechanical load, annealing, destruction of material, block structures, surface, multifractal formalism.
Changes in the ferromagnetic resonance and magnetic anisotropy spectra of multilayer heterostructures [CoFeB/SiO-=SUB=-2-=/SUB=-|Bi-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=-]-=SUB=-47-=/SUB=- when applying Fe/Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=- nanoparticles to their surface
Authors: Bezverkhny A. I.  , Morgunov R. B.
Published: January 2023

The ferromagnetic resonance method revealed an increase in the anisotropy constant of the heterostructure [CoFeB/SiO2|Bi2Te3]47 under the action of magnetic Fe/Fe3O4 nanoparticles deposited on the surface of the heterostructure by 20%. It has been established that a layer of Fe/Fe3O4 nanoparticles ~27 nm thick on a GaAs diamagnetic substrate has its own magnetic anisotropy caused by the magnetic dipole interaction between the particles. A layer of nanoparticles bound by magnetic dipole interaction forms an equivalent magnetic film, the scattering field of which changes the effective magnetic anisotropy of the heterostructure CoFeB/SiO2|Bi2Te3]47. Keywords: ferromagnetic resonance, magnetic anisotropy, multilayer heterostructures, magnetic dipole interaction, nanoparticles.
Phonon spectrum of La-=SUB=-2-=/SUB=-Ge-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=-: ab initio calculation
Authors: Chernyshev V.A.  , Petrov V.P.
Published: January 2023

Within the framework of the density functional theory ab initio calculation of the crystal structure, phonon spectrum, and elastic properties of lanthanum germanate La2Ge2O7 with a triclinic structure (sp. gr. P 1, no. 2) was carried out. The frequencies and types of fundamental modes are determined. From the analysis of the displacement vectors obtained from the calculation, the degree of participation of ions in each mode was determined. The calculations were performed for the first time. Experimental data on the IR and Raman spectra, as well as the elastic constants of La2Ge2O7, are absent in the scientific press. We used the CRYSTAL17 program designed for ab initio calculations of periodic structures within the framework of the MO LCAO approach. Keywords: rare-earth germanates, phonons, elastic constants, hybrid functionals.
Synthesis features, structure, magnetometry and NMR spectroscopy of nanowires of various types
Authors: Zagorsky D. L.  , Doludenko I. M.  , Khaibullin R. I.  , Chuprakov S. A.  , Gippius A. A.  , Zhurenko S. V.  , Tkachev A. V.  , Cherkasov D. A.  , Zhigalina O. M.  , Khmelinin D. N.  , Kanevsky V. M.  , Muslimov A. E.  , Panov D. V.  , Blinov I. V.
Published: January 2023

Various types of nanowires obtained by matrix synthesis --- homogeneous (from iron) and heterogeneous (layered) --- have been studied. A technique for obtaining arrays of layered nanowires with alternating thin layers of magnetic and non-magnetic metals (Co/Cu, Ni/Cu) has been developed and described. Microscopy methods (SEM and TEM with elemental analysis) have been used to study the topography of the resulting structures, the diameters of nanowires and the thicknesses of individual layers, and the features of interlayer interfaces. Methods of synthesis of nanowires with thin layers and clear boundaries are proposed --- dilution of the electrolyte, use of a reference electrode, control of the leaked charge. Layered nanowires have been studied by magnetometry methods and it has been shown that the magnetic properties of an array of layered nanowires (in particular, the direction of the axis of light magnetization in the Co/Cu-NP array) depend not only on the aspect ratio of the magnetic layer, but also on the ratio of the thickness of the magnetic metal layer to the thickness of a non-magnetic spacer (copper layer). The nuclear magnetic resonance (NMR) method was used to study two types of nanowires. The NMR method (on 59-Co nuclei) studied the layer structures of Co/Cu: it is shown that in nanowires with layers of smaller thickness (and, accordingly, with a large contribution of interfaces), a large proportion of Co atoms coordinated by Cu atoms is observed. The high proportion of atoms coordinated by copper suggests that an admixture of copper enters the cobalt layers. Homogeneous iron nanowires (NMR on 57-Fe nuclei) were compared with bulk iron samples. A shift of the line towards high frequencies (by 0.3 MHz) was detected, indicating an increase in the field by about 0.2 T. A significant broadening of the line and a decrease in the spin-lattice relaxation time may indicate a significant variation in the local magnetic field values. Keywords: nanowires, matrix synthesis, microscopy, elemental analysis, magnetic properties, NMR.
Ion-irradiation effect on electron transport in YBCO thin films
Authors: Antonov A. V.  , Masterov D.V.  , Mikhaylov A. N.  , Morozov S. V.  , Pavlov S.A.  , Parafin A.E.  , Tetelbaum D. I.  , Ustavschikov S.S.  , Yunin P.A.  , Savinov D.A.
Published: January 2023

The disorder effect on superconducting properties of thin-film YBCO nanostructures in external magnetic fields is experimentally studied. The disorder was produced by irradiation with xenon ions. The research included transport measurements of narrow bridges based on HTSC YBCO films (thickness 50 nm) in strong magnetic fields (up to 12 T). Thus, for samples with different degrees of disorder, critical dependences have been studied, i.e. the Hc2(T) phase-transition line, the Hirr(T) irreversibility line, etc. The dependences of the mean-free path and critical temperature on the concentration of defects created by ion irradiation have been experimentally studied. The experimental data are described using formulas obtained within the framework of well-known models, such as the Ginzburg-Landau theory, the Drude theory, and the Gorkov equations. Keywords: B HTSP, thin films, ion irradiation, defects, resistive measurements, upper critical field, line of irreversibility, vortices.
Features of epitaxial growth of YBCO in the windows of the preliminary topology mask
Authors: Masterov D. V.  , Pavlov S. A.  , Parafin A. E.
Published: January 2023

This work is devoted to the study of epitaxial YBCO films obtained by laser sputtering during deposition of YBCO into the windows of the special preliminary topology mask. The morphology of the surface of the obtained structures was studied by electron microscopy, the electrical characteristics of superconducting bridges were measured: the critical temperature and the critical current density. The possibility of forming YBCO structures of a given topology with defect-free regions of micron sizes while maintaining high electrophysical parameters of the superconductor is shown. This opens up the possibility of reproducibly forming submicron-scale elements in the created defect-free areas using ion etching or ion implantation. Keywords: nano- and microstructures, defects, growth in local areas, YBCO.
Computer simulation of nanoscopic phase-inhomogeneous states and phase diagrams of HTSC cuprates and nickelates
Authors: Moskvin A. S.  , Panov Yu. D.  , Ulitko V.A.
Published: January 2023

More than 35 years of experience in the study of cuprate superconductors shows that the main characteristics of the phase diagram can only be obtained by taking into account mesoscopic static/dynamic phase inhomogeneity as a key property of these materials. Within a minimal model for the CuO2/NiO2 planes with the on-site Hilbert space reduced to only three effective valence centers [CuO4]7-,6-,5- (nominally Cu1+,2+,3+) with different conventional spin and different orbital symmetry we propose a unified non-BCS model that allows one to describe the main features of the phase diagrams of doped cuprates within the framework of a simple effective field theory. Using Maxwell's construction, the global nature of the electronic phase separation in the CuO2 planes of HTSC cuprates is established, which makes it possible to understand and explain many fundamental features of the physics of the normal and superconducting state of cuprates, including the mechanism of formation of the HTSC and pseudogap phase. The features of phase-inhomogeneous states and their evolution with temperature and doping degree, including the special role of the impurity potential in cuprates/nickelates with nonisovalent substitution, are considered for particular examples of the charge triplet model in the framework of the classical Monte Carlo method. Keywords: cuprates, nickelates, effective field theory, phase diagram, phase separation, Monte-Carlo.
Experimental study of elements of a Josephson traveling-wave parametric amplifier on SQUID chains.
Authors: Yusupov R. A.  , Filippenko L. V.  , Fominskiy M. Yu.  , Koshelets V. P.
Published: January 2023

The issues of designing a Josephson traveling-wave parametric amplifier (JTWPA) based on a well-established technology of superconducting microcircuits with given and controlled parameters based on high-quality Nb-AlOx-Nb tunnel junctions are considered. This technology has been adapted and optimized to obtain structures with the required parameters and circuits with large number of tunnel junctions. To advance the technology, the basic elements of a promising JTWPA have been devel-oped, manufactured and studied. In direct current measurements, a number of super-conducting elements parameters were experimentally determined; these parameters are required for designing a JTWPA chips for microwave measurements. An original design of JTWPA based on a chain of SQUIDs in a coplanar line has been developed for implementation using the IRE niobium technology; the parameters of the main elements of the JTWPA have been determined. Keywords: Josephson travelling-wave parametric amplifiers (JTWPA), Josephson metamaterials (JMM), Josephson junctions (JJs), cold amplifier, coplanar lines, quantum noise, SIS, SQUIDs.
Influence of the contact resistance of the YBCO/Au interface on the transport and microwave properties of arrays of high-temperature Josephson junctions
Authors: Pestov E. E.  , Levichev M. Yu.  , Masterov D. V.  , Parafin A. E.  , Pavlov S. A.  , Khorshev S. K.  , Rogozhkina N. V.
Published: January 2023

The influence of the contact resistance of the interface of the YBCO/Au structure on the transport and microwave properties of arrays of high-temperature bicrystal Josephson junctions embedded in a coplanar transmission line has been studied. The current-voltage characteristics of Josephson structures fabricated using various technologies are studied: in situ and ex situ with annealing in an oxygen atmosphere. The results obtained can be used to create a quantum ac voltage generator based on high-temperature Josephson junctions. Keywords: high-temperature superconductors, Josephson junctions, microwave, contact resistance.
Josephson tunnel junctions with integral SIN shunting.
Authors: Shevchenko M. S.  , Filippenko L. V.  , Kiselev O. S.  , Koshelets V. P.
Published: January 2023

This work is devoted to the study of tunnel Josephson superconductor-insulator-superconductor (SIS) junctions with a new type of shunting based on the usage of an additional superconductor-insulator-normal metal (NIS) junction located around the SIS junction. Numerical calculations of the parameters of such shunted junctions were carried out and modeling of their IVC (current-voltage characteristics) was performed. The designed samples were manufactured, their parameters were studied. To investigate the behavior of junctions under the influence of high-frequency signals in the sub-THz range, their IVCs were measured. Keywords: Superconducting devices, superconductor-insulator-superconductor tunnel junction, Josephson effect, shunting of Josephson junctions.
Simulation of temperature distribution in a functional NbN nanoelement with an embedded normal metal region
Authors: Gurovich B. A.  , Goncharov B. V.  , Prikhodko K. E.  , Kutuzov L. V.
Published: January 2023

A simulation of the temperature distribution in a functional NbN nanoelement with a built-in normal metal region has been carried out. The functional element consists of two NbN nanowires with a thickness of 4 nm, located on a substrate of monocrystalline AL2O3. The wires are separated by a 10 nm thick dielectric layer. A region of normal metal is embedded in the lower nanowire using the ZA technology. An approximate estimate of the performance of functional nanostructures, for the creation of which such a hike is used, is given. Keywords: Thin superconducting NbN films, functional superconducting nanoelements from NbN, modeling of thermal processes.
Spin-wave resonances in a diffusion-sensitive epitaxial film YIG
Authors: Tikhonov V. V.  , Gubanov V. A.  , Sadovnikov A. V.
Published: January 2023

It is shown that in a tangentially magnetized film of iron yttrium garnet exist two types of resonances --- a homogeneous ferrimagnetic resonance in the region of the film's homogeneous magnetization (outside the diffusion layer), and inhomogeneous spin-wave resonance within the thickness of the diffusion layer. A method of calculating the magnetization distribution over the film thickness using measured frequencies of the spin-wave and ferrimagnetic resonances. The method of mathematical modeling has established that the magnetic inhomogeneity of the transition layer layer introduces significant distortions of the oscillation epure at the frequency of the spin-wave resonance, and the nature of the distortions significantly depends on the magnitude of the magnetizing field. The results of the conducted can be useful for nondestructive control of the layered structure of YIG epitaxial films. Keywords: yttrium iron garnet epitaxial films, exchange spin waves, spinwave electronics, magnonics.
Nonlinear effects of spin wave propagation in a bilayer magnon waveguide
Authors: Odintsov S. A.  , Lock E. H.  , Beginin E. N.  , Sadovnikov A. V.
Published: January 2023

The possibility of frequency-selective propagation of spin waves in a linear and nonlinear mode in a magnon microwave medium consisting of two layers with different values of the magnetization saturation of each layer is demonstrated. It is shown that multimode propagation of spin waves can be carried out inside the two-layer structure in two frequency ranges, with an increase in the power of the input microwave signal leading to a change in the boundaries of both frequency ranges. At the same time, this process is accompanied by a strong nonreciprocity of the spin-wave signal propagation, which manifests itself in a change in the amplitude-frequency characteristics when the direction of the external magnetic field is reversed, with a nonlinear mode change in the frequency bandwidth borders can change with increasing pumping power. The proposed concept of a two-layer spin-wave waveguide can form the basis for the fabrication of nonlinear magnon elements demonstrating interconnection functions with support for multiband modes of operation. Keywords: magnonics, nonlinearity, nonlinear systems, multilayer systems, spin waves.
Control of band gap's in a permalloy Structure by changing the meander profile
Authors: Gubanova Yu. A.  , Gubanov V. A.  , Noginova N.  , Sadovnikov A. V.
Published: January 2023

Control modes of band gap in meander-shaped permalloy (NiFe) thin films have been investigated by the method of micromagnetic modeling. The electrodynamic problem is considered by the finite element method and the dispersion characteristics of spin waves are obtained when the geometrical parameters of the meander are changed. The character of changes in the frequency ranges of the Bragg band gaps depending on the meander profile has been investigated. The results can be used to create devices for microwave signal processing, microwave filters and systems with spatio-temporal division of the signal. Keywords: spin waves, magnonics, meander structures, magnon crystal.
Peculiarities of the formation of band gaps in mul-timode regime of spin waves propagation in mag-nonic crystals
Authors: Martyshkin A.A.  , Beginin E. N.  , Sheshukova S.E.  , Sharaevsky Yu. P.  , Nikitov S.A.  , Sadovnikov A.V.
Published: January 2023

The dynamics of spin waves during their multimode propagation in a magnonic crystal, which is an irregular narrow ferrite waveguide with periodic boundary modulation, has been studied by the method of Mandelstam--Brillouin spectroscopy. The transformation of the mode composition of spin waves propagating in an irregular ferrite waveguide is shown. The space-time dynamics of spin waves and the characteristics of the band gaps of a magnonic crystal are experimentally studied, and the possibility of controlling the frequency-selective properties of such a structure is shown. By excitation of a superposition of even or odd width modes of the ferrite microstructure, it becomes possible to control the position of the band gaps of a magnonic crystal. The results of the experiment agree with the results of micromagnetic modeling of the propagation and transformation of the spectrum of spin waves propagating in a ferromagnetic periodic structure. Keywords: spin waves, magnonics, magnonic crystal, micromagnetic modeling.
Magnetic Moment Transformation in a Heterophase Nanomagnet GdFeCo|IrMn in the Vicinity of the Ferrimagnet Compensation Point
Authors: Gornakov V. S.  , Shashkov I. V.  , Kabanov Yu. P.  , Koplak O. V.
Published: January 2023

Ta|Pt|GdFeCo|IrMn|Pt multilayer structure with perpendicular magnetic anisotropy in vicinity of the ferrimagnet compensation temperature TK has been carried out. It has been established that the distribution of the magnetic moment in the GdFeCo ferrimagnetic film exchange-coupled to the IrMn antiferromagnet is largely determined by the magnitude and orientation of both the field applied during cooling from room temperature to T=2 K and the testing field over the entire temperature range. It is shown that the direction of the domain wall moving changes to the opposite one at a fixed value of the amplitude of the magnetic field pulse when the temperature passes through the TK. Keywords: ferrimagnets, heterostructures, perpendicular magnetic anisotropy, magnetic moment, compensation temperature, domain wall.
Synchronization of auto-oscillations of exchange-coupled magnetic vortices
Authors: Mironov V.L.  , Tatarskiy D.A.  , Fraerman A.A.
Published: January 2023

The results of micromagnetic modeling of the gyrotropic mode of magnetization auto-oscillations in overlapping ferromagnetic disks under the action of a spin-polarized current are presented. It is shown that the exchange interaction between disks significantly increases the binding energy of magnetic vortices and, as a consequence, reduces the dephasing of the vortex core gyration in neighboring disks. Keywords: vortex nanooscillator, auto-oscillations, synchronization, exchange coupling.
Ferromagnetic resonance in exchange-coupled magnetic vortices
Authors: Tatarsky D. A.  , Skorokhodov E. V.  , Mironov V. L.  , Gusev S. A.
Published: January 2023

The results of a study of low-frequency ferromagnetic resonance in a system of two overlapping permalloy disks by magnetic resonance force spectroscopy are presented. It is shown that the resonant frequency of the gyrotropic mode of oscillations of magnetic vortices in this system significantly depends on the vorticity of their shells. The experimental dependences of the resonant frequencies of various states on the external magnetic field are qualitatively consistent with the results of micromagnetic modeling. Keywords: ferromagnetic resonance, magnetic resonance force spectroscopy, magnetic vortices.
Superconducting bolometer with high-frequency readout circuit at 400 mK
Authors: Merenkov A. V.  , Kim T. M.  , Chichkov V. I.  , Kalinkin S. V.  , Shitov S. V.
Published: January 2023

The detection of a terahertz optical signal using a bolometric detector with a planar niobium resonator loaded with a hafnium micromotor using the nonlinearity of the impedance of an electron gas at a frequency of 1.5 GHz near the critical temperature of the micromotor is demonstrated for the first time. The temperature of the electron gas was shifted by the resonator current, and the superconducting transition of the micromotor occurred under the action of a terahertz signal. The test thermodynamic signal from a thin-film Fe-Cr-Ni absorber heated in the range of 1-10 K was focused from a distance of 10 mm with an immersion lens made of sapphire onto a planar antenna matched with a micro-bridge in the range of 600-700 GHz. The measured power transmission coefficient of the bolometer was +5.5 dB with a saturation power of ~1 pW and a threshold sensitivity of the receiving system (3±1)·10-17 W/sqrt(Hz)sqrt sqrt, which is close to the theoretical values for the investigated bridge with a size of 2.5x2.5x0.08 μm. The tested detector can be used to create imaging terahertz matrices with frequency multiplexing in sorption-type cryostats. Keywords: RFTES bolometer, superconducting micro bridge, high-frequency impedance of superconductor, hafnium film, electron gas, planar resonator, frequency multiplexing, planar antenna, black body, thermodynamic noise. Keywords: RFTES bolometer, superconducting microbridge, high-frequency impedance, hafnium film, electron gas, coplanar resonator, frequency-division multiplexing, planar antenna, blackbody, noise.
Spin magnetoresistance of a strontium iridate/manganite heterostructure
Authors: Constantinian K. Y.  , Ovsyannikov G. A.  , Shadrin A. V.  , Shmakov V. A.  , Petrzhik A. M.  , Kislinskii Yu. V.  , Klimov A. A.
Published: January 2023

The results of the angular dependences of the magnetoresistance of the SrIrO3/La0.7Sr0.3MnO3 heterostructure made of oxide thin films epitaxially grown on a NdGaO3 substrate are presented and discussed. The resistance of the heterostructure was measured in configuration of planar Hall effect with magnetic field applied in parallel making possible to estimate the spin-Hall angle. The contribution of the anisotropic magnetoresistance and the spin-Hall magnetoresistance occurred due to strong spin-orbit interaction in the SrIrO3 film were evaluated. Keywords: strontium iridate, spin-orbit interaction, spin magnetoresistance, spin-Hall angle.
Nature of electrotransport and mechanisms of relaxation in an alternating field in silver intercalated hafnium diselenide
Authors: Pleshchev V.G.
Published: January 2023

The features of charge transfer in electrochemical cells with electrodes of various types and with an intercalated compound AgxHfSe2 (x=0.1,0.2) as an electrolyte were studied by the method of impedance spectroscopy. Based on the analysis of the obtained data, the presence of mixed electron-ionic conductivity in this compound was shown, and the numbers of ionic and electron transfer in these compounds were determined for the first time. The different nature of relaxation processes in mixed and ionic charge transfer is shown. Keywords: hafnium diselenide, silver, intercalation, impedance, ionic and electronic conductivity.
Structure formation and depolarization relaxation processes in porous piezoactive polyvinylidene fluoride films
Authors: Gerasimov D. I.  , Kuryndin I. S.  , Lavrentyev V. K.  , Volgina E. A.  , Temnov D. E.  , Elyashevich G. K.
Published: January 2023

Piezoactive porous polyvinylidene fluoride films prepared in the process based on melt extrusion with subsequent isometric annealing, uniaxial extension and thermal fixation have been studied. It was shown that two competing orientation processes -polymorphous transition of non-polar α-phase into polar piezoactive β-phase and formation of porous structure - occur during the uniaxial extension of annealed films. It has been established that orientation degree of extruded films is the key factor determining the efficiency of both processes. Thermally stimulated depolarization method was used to investigate the dipole relaxation in oriented films, and activation energy of these processes was found. The films were polarized using corona discharge and high-voltage contact methods, both, and the dependence of piezoelectric modulus on the polarization conditions has been obtained. The maximum value of piezoelectric modulus d31=30.1 pC/N was achieved by polarization of films in corona discharge method. Keywords: polyvinylidene fluoride, porous films, supramolecular structure, piezoelectric properties, polarization, relaxation processes.
Radiation-Stimulated Transformations Yb-=SUP=-3+-=/SUP=-->Yb-=SUP=-2+-=/SUP=- and Yb-=SUP=-3+-=/SUP=-->Yb-=SUP=-3+-=/SUP=- in Single Crystals and Nanoceramics CaF-=SUB=-2-=/SUB=- : YbF-=SUB=-3-=/SUB=-
Authors: Ashurov M. Kh.  , Nuritdinov I.  , Boyboboeva S. T.
Published: January 2023

The radiation resistance of CaF2 : YbF3 (3 mol.% YbF3) laser ceramics and a single crystal of similar composition (3.6 mol.% YbF3) exposed to gamma rays in a 60Co source is studied. The non-irradiated samples have been shown to be similar in spectral characteristics. After the CaF2 : YbF3 crystals and ceramics γ-irradiation and the following time exposure, along with transformations Yb3+->Yb2+, configurational Yb3+->Yb3+ transitions between different states of Yb3+ ions in the structure of samples are carried out, with the participation of interstitial Fi ions. Keywords: radiation resistance, laser ceramics, gamma rays, spectral characteristics defects.
Sputtering and ripples formation by gas cluster ions on LiNbO-=SUB=-3-=/SUB=- crystal
Authors: Ieshkin A. E.  , Ilina T. S.  , Kiselev D. A.  , Senatulin B. R.  , Skryleva E. A.  , Suchaneck G.  , Parkhomenko Yu. N.
Published: January 2023

The work addresses the creation of surface structures on lithium niobate single crystals. Surface topography of lithium niobate surface sputtered with gas cluster ion beams was investigated. Surface ripples induced on the surface were analyzed using power spectral density functions approach, their evolution with ion fluence and their dependence on the cluster ion energy discussed. Sputter yield value was shown to decrease with surface roughness increase, the reasons of the effect are indicated. Local piezoresponse of the rippled surface was studied. Keywords: ferroelectrics, LiNbO3 crystal, gas cluster ions, self-organization, AFM, PSD function.
Variation of the micromechanics of impact fracture of MgAl-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=- in response to the applied hot isostatic pressing
Authors: Shcherbakov I.P.  , Afanaseva E.V.  , Dunaev A.A.  , Eronko S.B.  , Kadomtsev A.G.  , Narykova M.V.  , Chmel A.E.
Published: January 2023

The MgAl2O4 ceramics produced by the preliminary clinkering of synthesized powder was exposed to the hot isostatic pressing (HIP). Samples were subjected to a pointed impact loading, which excited the acoustical and electromagnetic emissions (AE and EME, respectively). In non-HIP-treated samples, the energy distribution in time series of AE and EME pulses followed an exponential law, while after an application of the hot isostatic pressing procedure, the emissions of both types exhibited the power law energy distributions in time sweeps. A variation of the specificity of the impact-induced AE/EME energy release was explained by a transition from the nucleation/decay of microcracks in non-HIP-treated ceramics to the self-organized dislocation folding directed to grain boundaries in the material characterized by the density that was close to that of a MgAl2O4 single crystal. Keywords: MgAl2O4 ceramics, hot isostatic pressing, impact loading, acoustic emission, electromagnetic emission.
Effect of boron doping on luminescent properties of silicon--vacancy and germanium--vacancy color centers in diamond particles obtained by chemical vapor deposition
Authors: Grudinkin S. A.  , Feoktistov N. A.  , Bogdanov K. V.  , Baranov A. V.  , Golubev V. G.
Published: January 2023

The effect of doping with boron on the luminescent properties of diamond particles synthesized by Hot Filament Chemical Vapor Deposition technique with color centers embedded during the growth process has been studied. It is shown that at low boron doping level, the photoluminescence intensity of a narrow zero-phonon line of the silicon-vacancy color center (738.2 nm) demonstrates a strong dependence on the concentration of boron atoms at the sites of the diamond lattice. The dependence of the intensity of a broad photoluminescence band in the wavelength range 520-800 nm on the concentration of boron atoms in the gas mixture in the range from 14 to 64000 ppm has been analyzed. The Raman scattering spectra of the obtained particles have been studied. At the concentration of boron atoms in the gas mixture up to 1540 ppm, the Raman scattering spectra of diamond particles practically do not change when the boron concentration is varied. At high boron doping level, the diamond band in the Raman spectra exhibit a spectral response typical of the Fano resonance. Keywords: diamond particles, color centers, boron doping, photoluminescence, chemical vapor deposition.
Wave-like destruction on the input surface of optical media by powerful nanosecond laser pulses as a manifestation of stimulated radial scattering in the surface layer
Authors: Bykovsky N.E.
Published: January 2023

The wave-like damage structures on the entrance surface of optical media, which observed in various experimental studies with nanosecond laser pulses, are analysed. Sometimes such structures appear as a system of straight lines intersecting at the an-gles defined by the crystallography of a sample. It is proposed that stimulated radial scattering in a surface layer of a sample is responsible for their formation. Keywords: stimulated radical scattering, wave beating in the surface layer, plastic deformation.
Estimation of the temperature band characterizing the liquid--glass transition interval for chalcogenide glasses
Authors: Mashanov A.A.  , Darmaev M.V.  , Lybsanova A.B.
Published: January 2023

The temperature dependence of the viscosity of inorganic glasses in the glass transition region is successfully described by the Williams--Landel--Ferry (WLF) equation. For the studied glasses, the value of f_g=1/C1 weakly depends on the nature of the glasses. There is a linear correlation between delta delta Tg and Tg. From the data on the parameters of the WLF equation C1 and C2, we calculated delta delta Tg, as well as the relaxation time of the structure taug at the glass transition temperature of the glasses under study. Keywords: Viscosity in the glass transition region, Williams--Landel--Ferry equation, kinetic glass transition criterion, chalcogenide glasses, fluctuation volume fraction, liquid--glass transition.
Electron Transport Mechanisms in Polyethylene Terephthalate Membranes
Authors: Fedotov A. K.  , Movchan S. A.  , Apel P. Yu.  , Fedotova J. A.  , Pashkevich A. V.
Published: January 2023

This paper describes carrier transport mechanisms in polyethylene terephthalate (PET) films and porous PET-based membranes (PMs) obtained by irradiating pristine PET film with swift heavy ions, with subsequent chemical etching in an alkali (NaOH) solution. The obtained PMs had through nanochannels (pores) with an average diameter of 720-750 nm. We observed that in the temperature range 240-300 K, the current-voltage characteristics I(V) of the initial Cu|PET|Cu structure obeyed the improved Mott--Gurney law, which is based on the Mark--Helfrich model for a space-charge-limited current (SCLC) mechanism for electron transport. It was found for the first time that creation of nanochannels in PMs resulted in a significant increase in the electric current density (by about three orders of magnitude) while maintaining the SCLC mechanism. The enhanced current density is explained by the formation of a highly conductive layer along the inner surface of the walls of the nanochannel that are covered with carboxyl end groups, which are created by alkaline hydrolysis. According to the model, the surface states formed by these groups enable the drift of additional electrons injected from the copper electrodes under the action of the bias voltage. Keywords: polyethylene terephthalate, electron transport, space-charge-limited current mechanism, Mark--Helfrich injection model.
Nonlinear dynamics of an individual Portevin--Le Chatelier deformation bands
Authors: Shibkov A. A.  , Zolotov A. E.  , Gasanov M. F.  , Denisov A. A.  , Koltsov R. Y.  , Kochegarov S. S.
Published: January 2023

Based on high-speed studies of the dynamics of Portevin--Le Chatelier ambryo bands with a temporal resolution of up to 20 μs and a spatial resolution of up to 10 μm/px, their classification is proposed, which includes four types of bands depending on the nature of interaction with other bands and the sample surface (using the example of a polycrystalline aluminum-magnesium alloy). It has been found that all types of ambryo bands demonstrate nonlinear dynamics with a sharp acceleration of the band tip and the growth rate of its volume at the final stage before reaching the sample surface. A phenomenological model of the nonlinear growth of the ambryo band is proposed, which explains the exponential self-acceleration stage observed experimentally. The sharp absorption of acoustic noise at the stage of accelerated band growth is discussed. Keywords: nonlinear dynamics, Portevin--Le Chatelier effect, deformation ambryo bands, acoustic emission, dislocation mobility, aluminum-magnesium alloy.
On the possibility of the phonon mechanism of superconductivity in cuprate VTSP
Authors: Lykov A. N.
Published: January 2023

Some features of the electron-phonon mechanism in cuprate high-temperature superconductors (HTS) are considered to explain their properties. It is shown that the interaction of electrons with weakly fixed oxygen ions in the crystal lattice can lead to a strong electron-phonon interaction, and this explains the high critical temperatures in cuprate HTS. Based on this approach, the presence of a Tc maximum in the homologous series of cuprate HTSPS is explained and a method for searching for new HTSPS with higher critical temperatures is proposed. Keywords: high-temperature superconductivity, electron--phonon interaction, boundary conditions, Ginzburg--Landau theory, oxygen ions, "jelly" model.
Influence of the Degree of Phase Transition Diffuseness on the Depolarization Temperature in Relaxors of Different Types
Authors: Kamzina L.S.
Published: January 2023

The relationship between the temperatures of depolarization (Td) and morphotropic phase transition (TF-R) in crystalline relaxor solid solutions of various types, such as PbMg1/3Nb2/3O3-29PbTiO3 (PMN-29PT), PbZn1/3Nb2/3O3-9PbTiO3 (PZN-9PT) and NaBi1/2Ti1/2O3-xBaTiO3 (x=5,7.5%) (NBT-xBT) has been studied. For this purpose, dielectric measurements of polarized samples were carried out, and the process of induction of the ferroelectric phase in an electric field applied below the TF-R temperature was also studied. It was found that the structure of the low-temperature phases in these compounds is different, which leads to significant differences not only in the induction of the ferroelectric phase, but also to different relative positions of the temperatures Td and TF-R. In PMN-29PT, the formation of ferroelectric phases is preceded by some delay time, which is one of the hallmarks of a non-ergodic glassy phase, and in this case the temperatures Td and TF-R coincide. In PZN-9PT and NBT-5BT, the ferroelectric phase is induced immediately after the field is applied without a delay time, which indicates that below the TF-R temperature, the non-ergodic glassy phase does not appear, and the temperatures Td and TF-R do not coincide in them. The results obtained are discussed from the point of view of different degrees of diffuseness of the phase transition and different sizes of the polar regions. It is suggested that the coincidence of temperatures Td and TF-R is a consequence of the non-ergodic glassy phase and the small sizes of the polar regions. Keywords: relaxors, phase transitions, degree of smearing, depolarization temperature.
Evolution of the defective structure during long-term loading of ultrafine-grained titanium VT1-0 obtained by intensive plastic deformation
Authors: Betekhtin V.I.  , Kadomtsev A. G.  , Narykova M. V.  , Lihachev A. I.  , Amosova O. V.  , Saenko M. Yu.  , Kolobov Yu. R.
Published: January 2023

For high-strength titanium VT1-0, the ultrafine-grained structure of which was obtained by mechanical-thermal treatment using the methods of helical and longitudinal rolling followed by annealing to relieve stress of the first kind. The effect of long-term loading in the creep mode at elevated temperature on the size and shape of grains has been studied. A similar study was previously carried out for recrystallized coarse-grained titanium transferred from the ultrafine-grained state by isothermal annealing. Based on the data obtained in the work and the previous results of the authors, the factors affecting the mechanical stability (durability) of ultrafine-grained metals obtained under severe plastic deformation were analyzed. Keywords: creep, durability, nanopores, ultrafine-grained metals, titanium, recrystallization.
Polymorphic transformations in iodine titanium
Authors: Spivak L. V.  , Kirchanov V. S.  , Shchepina N. E
Published: January 2023

Based on the analysis of differential scanning calorimetry data, the possibility of classifying the observed endothermic or exothermic transformations as phase transformations of the first oder is considered. Two approaches have been implemented. The first is based on the correspondence between the temperatures of the maximum conversion rate and the temperatures of the extrema on the second derivative of the differential scanning calorimetry signal with respect to temperature. In the second approach, the phase transformation is considered as a kind of kinetic reaction of a chemical process with the determination of some parameters included in the kinetic equations. In this case, the order parameter of such reaction n is obtained from the analysis of the differential scanning calorimetry signal shape in the region of phase transformation registration temperatures. Using the example of experiments carried out during thermal cycling of titanium iodide samples, it is shown that both the first and second approaches make it possible to fairly adequately attribute the processes that cause calorimetric effects on the dependences of differential scanning calorimetry to first-order phase transitions. In particular, the obtained results of differential scanning calorimetry during heating and cooling of iodide titanium show that polymorphic transformations in it are realized by various mechanisms depending on the rate of thermal cycling and the thermal history of the metal. Keywords: activation energy, titanium, calorimetry, polymorphism, structure, approximation.
Exchange interaction in LaCoO-=SUB=-3-=/SUB=- between cobalt ions Co-=SUP=-3+-=/SUP=- in different spin states
Authors: Polukeev S. I.  , Gavrichkov V. A.  , Ovchinnikov S. G.
Published: January 2023

The values and signs of the contributions to the superexchange interaction of Co3+ ions in LaCoO3 in different spin states, namely, the superexchange of a pair of ions in the intermediate (IS) state and the superexchange of a pair of ions, one of which is in the intermediate state and the other in the high-spin (HS) state, are studied. For this purpose, virtual electron-hole pairs produced in the course of superexchange (the so-called exchange loops) have been studied within the framework of a multiband generalization of the Hubbard model. It is shown that the cobalt ions in the intermediate state are ordered ferromagnetically, while a pair of ions in different HS and IS states makes an AFM contribution to the superexchange. Keywords: superexchange interaction, magnetic structure, Hubbard model, projection operator method, exchange loop.
Ferroelectric hysteresis and magnetoelectric effect in orthorhombic Dy-=SUB=-1-x-=/SUB=-Ho-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=- single crystals
Authors: Freydman A. L.  , Horoshiy I. N.  , Kolkov M. I.
Published: January 2023

In Dy1-xHoxMnO3 single crystals with the orthorhombic space group Pbnm, ferroelectric hysteresis loops were measured for compositions with x=0 and 0.3. As the content of Ho3+ ions increases, the hysteresis loop narrows and for x=0.3 it no longer manifests itself. An analysis of the signal corresponding to the hysteretic behavior of a ferroelectric showed that even harmonics can be obtained only if the hysteresis loop is not symmetric about the abscissa axis. In view of the latter, the hypothesis that the second harmonic of the magnetoelectric effect is a consequence of the complex dependence of the polarization on time due to its hysteresis becomes doubtful. Measurements of the dependence of the inverse magnetoelectric effect on the amplitude of the applied electric field Delta M(E) showed that the first harmonic remains linear with respect to the electric field even in the electric field strength region where the domain structure of the ferroelectric is rearranged. Keywords: multiferroics, ferroelectricity, hysteresis.
Raman and Photoluminescence Spectra for Ho, Er, Tm, Yb, Lu, and Y doped Hafnia
Authors: Shkerin S.N.  , Meshcherskikh A.N.  , Yaroslavtseva T.V.  , Abdurakhimova R.K.
Published: January 2023

Previously obtained and certified HfO2 based samples were investigated by two Raman spectrometers with different wave source. Stokes reflexes have to be independent of the laser frequency so they were distinguished by comparison of different laser results. For the first time the dependence of Stokes lines frequencies on the cation radii of dopants was observed. Frequencies monotonically varied with the ratio of cation-dopant to hafnium radii changes. All non-Stokes reflexes are considered as photoluminescence. They were compared with both the literature data on luminescence of REM cations and the experimental results on zirconia-based materials intrinsic photoluminescence, which was a property of its point defects. Intrinsic photoluminescence is observed for the first time on hafnia-based materials. Keywords: Raman spectroscopy, luminescence, hafnia with cubic structure, REE.
Phase transitions in a two-dimensional antiferromagnetic Potts model on a kagome lattice
Authors: Ramazanov M.K.  , Murtazaev A.K.  , Magomedov M.A.  , Rizvanova T.R.
Published: January 2023

The phase transitions and thermodynamic properties of the two-dimensional antiferromagnetic Potts model with the number of spin states q=4 on the kagome lattice are studied by the Monte Carlo method, taking into account the exchange interactions of the first J1 and second J2 nearest neighbors. The studies were carried out for the value of the interaction of the second nearest neighbors in the interval -1.0≤ J_2≤0.0. An analysis of the character of phase transitions has been carried out. It is shown that in the interval -1.0≤ J_2≤-0.1, a second-order phase transition is observed, while at J_2=0.0, frustrations disturb the order in the system and lead to the disappearance of the phase transition Keywords: Frustration, phase transition, Monte Carlo method, Potts model.
Electron Diffraction Study of transformation the reconstruction 6 3 on 4H-SiC(0001) in quasi-free-standing epitaxial graphene
Authors: Kotousova I. S.  , Lebedev S. P.  , Antipov V. V.  , Lebedev A. A.
Published: January 2023

Through the agency of reflection high-energy electron diffraction (RHEED) we have studied the transformation of the reconstruction 6 3 grown on substrate 4H-SiC in an Ar medium with a short sublimation annealing time in quasi-free-standing epitaxial graphene due to the use of hydrogen intercalation. It was found that grown reconstruction layer was not uniform. The comparison of the results of the structural study of quasi-free-standing graphene and single-layer graphene on buffer layer has been made. Keywords: SiC, reconstruction, intercalation, graphene, RHEED.
Conduction band electronic states of ultrathin thiophene-phenylene co-oligomer and substituted biphenyl films on the surface of layer-by-layer grown ZnO
Authors: Komolov A.S.  , Lazneva E.F.  , Gerasimova N.B.  , Sobolev V.S.  , Zhizhin E.V.  , Pudikov D.A.  , Pshenichnyuk S.A.  , Asfandiarov N.L.  , Borshchev O.V.  , Ponomarenko S.A.  , Handke B.
Published: January 2023

The results of studying the electronic states of the conduction band and interface potential barrier during the formation of ultrathin films of thiophene-phenylene co-oligomer CH3-phenylene-thiophene-thiophene-phenylene -CH3(CH3-PTTP-CH3) on the surface of ZnO and films of biphenyl tetracarboxylic dianhydride (BPDA) on the ZnO surface are presented. A 100 nm thick ZnO layer was prepared by atomic layer deposition (ALD). Organic CH3-PTTP-CH3 films and BPDA films up to 8 nm thick were formed by thermal vacuum deposition. During film deposition, the electronic characteristics of the surface were studied using total current spectroscopy (TCS) in the energy range from 5 eV to 20 eV above EF. In this energy range, the structure of the maxima of the unoccupied electronic states of CH3-PTTP-CH3 and BPDA films was determined. As a result of the CH3-PTTP-CH3 film deposition, a decrease in the work function to 4.0 eV was found, compared with the value of the work function of 4.2 eV measured from the ALD ZnO-substrate. This corresponds to the transfer of a negative charge from the CH3-PTTP-CH3 film to the substrate. The charge transfer at the interface between the BPDA film and the ALD ZnO-substrate occurs in the opposite direction, since a 4.7 eV increase of the work function was registered during the formation of this interface. The CH3-PTTP-CH3 and BPDA films studied and the layer-by-layer grown ZnO film represent a continuous coating on sufficiently large surface areas of the order of 10 μmx10 μm. The roughness of the ZnO surface does not exceed 4 nm, and the surface roughness of CH3-PTTP-CH3 and BPDA films was 10-15 nm. Keywords: thiophene-phenylene co-oligomers, biphenyl tetracarboxylic dianhydride, ultrathin films, ZnO, atomic layer deposition method, electronic properties, low-energy electron spectroscopy, interface potential barrier.
Phase transitions and phase transformations in the phase separation nanoregions in ErMn-=SUB=-2-=/SUB=-O-=SUB=-5-=/SUB=- multiferroics
Authors: Khannanov B.Kh.  , Sanina V.A.  , Golovenchits E.I.  , Lushnikov S.G.
Published: January 2023

The effect of the rare-earth ion Er3+, which has a large orbital contribution to the magnetic moment, were studied to phase transitions and phase transformations of 2D nanoregions of phase separation in the ErMn2O5 multiferroic. These nanoregions are the semiconductor heterostructures (superlattices) and are formed due to self-organization processes in the ErMn2O5 matrix. Significant effect of Er3+ ions, the moments of which are rigidly oriented along the c axis of the crystal, on the magnetic dynamics, heat capacity and multiferroic properties of layers superlattises was found at a wide temperature range 5-300 K in ErMn2O5 multiferroics. Keywords: multiferroic, 2D phase separation nanoregions, semiconductor-heterostructures, superlattices, phase transitions, phase transformations.