bluuebunny/crossref_metadata_2025 huggingface dataset:
Site dominant frequencies in Lima, Peru, by h/v spectral ratio of seismic records
Authors: Ccahua-Laqui Angel Leandro , Gonzales-Trujillo Carlos Eduardo , Moya-Huallpa Luis Angel , Lazares-La Rosa Luis Fernando , Yamazaki Fumio
Published: January 2023

Strong motion records are important for improving seismic design, damage assessment and analysis of earthquake effects. Despite the relevance of having strong motion networks, their implementation in Peru has been performed in the very recent years. For instance, only five strong motion stations in Lima recorded the 2007 Mw 7.9 Pisco earthquake, whereas 55 stations recorded the 2021 Mw 6.0 Mala earthquake. The current number of instrumentations in Lima city provides an opportunity to improve soil characterization. This study aims to determine the dominant frequency (fd) of the seismic stations located in Metropolitan Lima. The procedure we adopted, first considered collecting, for an arbitrary station, all the available events recorded from 2011-2021, including the 2007 Mw 7.9 Pisco earthquake. Then, the pseudo spectral acceleration, using 5% damping, for each component were computed, and the horizontal-to-vertical (H/V) spectral ratios were calculated. Finally, the average H/V spectral ratio was used to adequately characterize the values of fd . In total, we evaluated 51 stations throughout Lima city. Values of  fd lower than 1 Hz were observed for the coastal areas in which the underlying soil consist of clayey/sandy deposits and regions with an important impedance contrast in the deeper part of the substructure. These values increment towards the center of the city coinciding with surficial gravel deposits.
Seismic analysis of underground structures: Influence of the soil type, the relative stiffness and seismic intensity
Authors: Garcia Velasquez Jhonatan Smith , Scaletti Farina Hugo Victor
Published: January 2023

Las estructuras subterráneas se desempeñan como medios para llevar a cabo actividades esenciales en una sociedad moderna. Por lo tanto, su apropiado desempeño sísmico es importante para la reducción del riesgo de desastres. El presente trabajo trata sobre los efectos sísmicos sobre las estructuras subterráneas ubicadas en zonas altamente sísmicas, como la costa del Perú. Se empleó el programa de cómputo FLAC para realizar varios análisis dinámicos de estructuras subterráneas de sección rectangular, considerando condiciones de borde de tipo campo libre y el comportamiento no lineal e inelástico del suelo ante siete sismos ajustados a un mismo espectro objetivo. Dichos análisis se llevaron a cabo variando factores como el tipo de suelo (homogéneo o estratificado), la geometría y espesores de la estructura y el periodo de retorno del sismo. Se ha encontrado que  cuando la estructura está implantada en suelo homogéneo las fuerzas y desplazamientos presentas poca variación. Sin embargo, cuando la estructura está en suelo heterogéneo los resultados muestran variaciones importantes. De manera que el ajuste a un mismo espectro elástico no implica uniformizar la demanda sísmica. La geometría de la estructura y el espesor de los muros tienen considerable influencia. En suelos heterogéneos las estructuras muy flexibles pueden tener grandes deformaciones que implicarían niveles de daño importante.
Metodos de identificacion modal en puentes atirantados caso de estudio: Puente Rayitos de Sol
Authors: León Deza Julio Alfredo , Melchor Placencia Carlos Javier , Sánchez Moya Víctor
Published: January 2023

La estimación precisa de los parámetros modales de los puentes atirantados juega un papel clave en la evaluación de la seguridad de estas estructuras bajo cargas dinámicas como el tráfico, el viento y los terremotos. Además, la dificultad para excitar este tipo de estructura hace que las mediciones de vibraciones ambientales sean una fuente significativa de información para validar los modelos de elementos finitos tridimensionales completos desarrollados que se utilizan para evaluar la respuesta dinámica de este tipo de puentes. En este trabajo se seleccionó como caso de estudio el puente atirantado Rayitos de Sol. Para evaluar los parámetros modales del puente, se recolectaron datos de vibraciones ambientales de puntos estratégicos sobre la plataforma. Utilizando los datos registrados en campo, se llevaron a cabo y luego se compararon una serie de métodos de identificación de sistemas en el dominio del tiempo y la frecuencia. Los datos recopilados se analizaron en función de métodos de identificación only-output: selección de picos, descomposición del dominio de la frecuencia, identificación del subespacio estocástico, decremento aleatorio e identificación del dominio del tiempo de Ibrahim. El propósito de realizar diferentes análisis es examinar la eficacia y los límites de aplicabilidad de estas técnicas para abordar los desafíos específicos involucrados en la identificación modal de puentes por etapas. Para complementar el análisis de datos de vibraciones ambientales, el modelo de elementos finitos validado del puente se sometió a excitaciones ambientales artificiales para realizar una comparación exhaustiva de los métodos de identificación. En el desarrollo del modelo numérico, considerar la rigidez efectiva de los elementos de hormigón armado, así como modelar las condiciones de contorno correctas en las juntas de dilatación, fueron los principales factores para lograr una buena correlación con los parámetros modales medidos.
Synthesis and Characterization of Molecularly Imprinted Polymers (MIPs) Using Humic Acid
Authors:   Study Programme of Cosmetic Engineering, Institut Teknologi Sumatera, South Lampung 35365, Indonesia, Putri Tikarahayu , Ali Zulfikar Muhammad ,   Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, West Java 40132, Indonesia, Wahyuningrum Deana ,   Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, West Java 40132, Indonesia, Syahjoko Saputra Iwan ,   Study Programme of Cosmetic Engineering, Institut Teknologi Sumatera, South Lampung 35365, Indonesia
Published: January 2023

MIPs was synthesized through microwave assisted organic synthesis (MAOS) method by using methyl methacrylate (MMA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker, benzoyl peroxide (BPO) as initiator, N,N-dimethyl formamide (DMF) as porogen solvent, and (HA) as template. The MIPs was successfully synthesized according to the characterization using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), electron dispersive spectrometer (EDS), and UV spectrophotometer. FTIR shows the other functional groups peaks in the FTIR spectra of NIPs and MIPs after leaching were appeared at the wavelength of 2955 cm-1 corresponded to stretching vibration of C-H of 1459 cm-1 and 1160.06 cm-1 corresponded to the vibration bands of CH3 and O-CH3. EDS shows the MIPs after leaching have the elemental compositions of C, O, and Si with a mass of 78.34, 21.43, and 0.23%. UV spectrum shows the MIPs and NIPs have absorbance values of 0.36 nm and 0.44 nm.
Radiation treatment of the edges of a crack in a superconducting layer during restoration of HTSC tape
Authors: Podlivaev A. I.  , Rudnev I. A.
Published: January 2023

Numerically, within the framework of the critical state model, the density of superconducting currents in a second-generation HTSC tape based on GdBa2Cu3O7-x is determined. It is shown that during the restoration of the transverse crack of the superconducting layer by shunting the crack with a piece of defect-free tape, the critical current of the restored area decreases by ~8%. It is shown that preliminary i rradiation of the crack edges with ions of hydrogen, helium, neon, and oxygen makes it possible to restore the initial value of the critical current. The calculation of the effect of radiation on a superconducting tape was carried out using the SRIM software package. Keywords: high temperature superconductor, irradiation, radiation defects, critical current.
Boundary conditions for scattering problems of exchange spin waves in inhomogeneous magnetic structures
Authors: Poimanov V. D.
Published: January 2023

A method for obtaining boundary conditions for magnetization in ferromagnetic structures with an inhomogeneous ground state --- a relativistic and exchange spiral caused by the presence of competing exchange interactions --- is proposed in this paper within the framework of a lattice model with a subsequent passage to the limit to the continuum. It is shown that such conditions are the equations of the dynamics of the magnetization of those boundary spins in which the symmetry is broken in comparison with the internal ones. Keywords: scattering of exchange spin waves, exchange spiral, relativistic spiral, boundary conditions for magnetization.
Electrical and magnetic properties of intercalated compounds in the Gd-=SUB=-x-=/SUB=-NbSe-=SUB=-2-=/SUB=- system (0≤ x≤0.33)
Authors: Pleshchev V.G.
Published: January 2023

The electrical and magnetic properties were measured on polycrystalline samples of niobium diselenide intercalated with gadolinium atoms. The dependences of the electrical resistance on temperature point to a predominantly phonon scattering mechanism for charge carriers, while the concentration dependences are determined by increasing scattering by interstitial atoms. The magnetic properties of GdxNbSe2 (0≤ x≤0.33) were studied in the temperature range of 2-350 K and in the range of magnetic fields up to 70 kOe. Based on the results of studies of magnetic susceptibility and magnetization, the possibility of the existence of antiferromagnetic interactions in the studied compounds and the phenomenon of spin reorientation in a magnetic field are shown. The observed decrease in the effective magnetic moment of gadolinium ions with an increase with their concentration is discussed in terms of a possible intramolecular exchange. Keywords: niobium diselenide, gadolinium, intercalation, electrical resistance, magnetization, effective magnetic moment.
Analysis of magnetocaloric effect in ferromagnetic shape memory alloy crystals
Authors: Malygin G. A.
Published: January 2023

In the framework of the theory of diffuse martensitic transitions to be based on thermodynamic and kinetic relationships the mechanism of the magnetocaloric (MC) effect in shape memory ferromagnetic alloy crystals is theoretically analysed. The theory adequately describes magnetostructural transformations and MC effect in these crystals at adiabatically applying to them and eliminating from magnetic field. The analysis also includes magneto-anisotropic crystals how to be according to literature data crystals Ni49.5Mn25.4Ga25 alloy. Keywords: magnetocaloric effect, magnetostructural martensite transitions, magneto-anisotropic crystals, isothermal entropy change.
Ab initio calculations of electronic properties, frequency dispersion of dielectric coefficients and the edge of the optical absorption of TlInS-=SUB=-2-=/SUB=- single crystals
Authors: Mustafaeva S. N.  , Asadov M. M.  , Huseynova S. S.  , Hasanov N. Z.  , Lukichev V. F.
Published: January 2023

Calculations of the band structure and density of states for supercells of TlInS2 and TlInS2 semiconductor crystals with monoclinic singony within the density functional theory (DFT) are presented. In DFT calculations, the Coulomb repulsion (the Hubbard parameter (U)) was taken into account in order to correctly describe the band gap (Eg) of crystals. It is shown that the maximum of the valence band and the minimum of the conduction band of TlInS2 are located at the center (point ) of the Brillouin zone, which points to the direct energy of the band gap of the TlInS2 and TlInS2 crystals. Thrue results of calculating the band structure and features of the distribution of the density of electronic states in TlInS2 and TlInS2 are discussed. TlInS2 single crystals doped with 0.1 mol.% tin (TlInS2<0.1 mol.% Sn>) were synthesized and then grown by the Bridgman--Stockbarger method. The frequency dispersion of the dielectric coefficients and conductivity of a TlInS2 and TlInS2<0.1 mol.% Sn> single crystals in the frequency range f=5·104-3.5·107 Hz is studied. It is shown that relaxation losses occur in TlInS2. A hopping mechanism of ac charge transfer in TlInS2 has been established. In TlInS2, the parameters of localized states, such as the density of states near the Fermi level and their energy spread, the average hopping time and distance, and the concentration of deep traps, are estimated. The optical properties of TlInS2 and TlInS2<0.1 mol.% Sn> single crystals have been studied. The values of Eg for direct optical transitions in TlInS2 and TlInS2<0.1 mol.% Sn> crystals were obtained from the optical absorption spectra. It has been shown that the introduction of 0.1 mol.% Sn, which replaces indium atoms, into TlInS2 reduces the value of Eg, for example, at 150 K from 2.539(TlInS2) to 2.486 eV (TlInS2<0.1 mol.% Sn>). From optical measurements, the average temperature coefficient of the band gap d Eg/d T=-7·10-4 eV/K for TlInS2 was calculated. The decrease in the band gap of the TlInS2Sn> single crystal with respect to TlInS2 is 16 meV at 300 K and 53 meV at 150 K. Keywords: supercell, semiconductor TlInS2, tin doping, monoclinic syngony, density functional theory, electronic structure, single crystals, dielectric properties, optical absorption, charge transfer, parameters of localized states.
Peculiarities of the induced phase transition in single-crystal solid solutions Na-=SUB=-1/2-=/SUB=-Bi-=SUB=-1/2-=/SUB=-TiO-=SUB=-3-=/SUB=--5 %BaTiO-=SUB=-3-=/SUB=-
Authors: Kamzina L. S.
Published: January 2023

The dielectric and optical properties, as well as the time dependences of the permittivity in an electric field applied along the [001] direction, are studied in Na1/2Bi1/2TiO3-5 %BaTiO3 single crystals lying near the morphotropic phase boundary. It is shown that, even in the absence of an electric field, dielectric and optical hysteresis associated with the coexistence of tetragonal and rhombohedral phases is observed in a wide temperature range, and the relative volume fractions of the two phases largely depend on temperature. It was found that at temperatures below the temperature of the morphotropic phase transition, the induction of the ferroelectric phase occurs without a delay time, which distinguishes the samples under study from PbMg1/3Nb2/3O3-xPbTiO3 solid solutions. The results obtained are explained by different sizes of polar nanoregions in the low-temperature phase. Keywords: ferroelectricity, relaxors, induced phase transition.
Effect of graphene platelets pullout from ceramic matrix on the fracture toughness of ceramic/graphene composites
Authors: Bobylev S. V.
Published: January 2023

A theoretical model is proposed that describes the effect of graphene platelets pullout on the fracture toughness of ceramic/graphene composites. The dependences of fracture toughness on the graphene concentration and the dimensions of graphene platelets are calculated using a yttria-stabilized zirconia (YSZ)/graphene composite as an example. Calculations predict that if graphene platelets pullout from ceramic matrix is the dominant mechanism, then the maximum fracture toughness is achieved in the case of the longest and thinnest possible graphene platelets, provided that the latter have sufficient strength and adhesion to the matrix. The model shows a good correlation with experimental data at low graphene concentrations. Keywords: composites, graphene, ceramics, cracks, fracture toughness.
Sheet Resistance and Magnetoresistance in Polycrystalline CVD Graphenes
Authors: Fedotov A. K.  , Kharchanka A. A.  , Gumiennik U. E.  , Fedotova J. A.  , Ronassi A. A.  , Fedotov A. S.  , Prischepa S. L.  , Chichkov M. V.  , Malinkovich M. D.
Published: January 2023

Temperature and magnetic field dependencies of sheet resistance R#(T,B) in polycrystalline CVD graphene, investigated in the range of 2≤ T≤ 300 K and magnetic fields 0≤ B≤ 8 T, allowed to determine carrier transport mechanisms in single-layered and twisted CVD graphene. It is shown that for R#(T,B) curves for such samples are described by the interference quantum corrections to the Drude conductivity independently on type of precursor and peculiarities of graphene transfer from Cu foil onto the various substrates (glass or SiO2). The twisted CVD graphene samples have demonstrated additional contribution of 2D hopping conductivity into the R#(T,B) dependencies. Keywords: graphene, single layer, twisted layers, CVD, carrier transport, magnetoresistance.
Superconductivity and Phase Diagram in the Nanostructured Eutectic Ga-Ag Alloy
Authors: Smetanin D. V.  , Likholetova M. V.  , Charnaya E. V.  , Lee M. K.  , Chang L. J.  , Shevchenko E. V.  , Kumzerov Yu. A.  , Fokin A. V.
Published: January 2023

Here, we present a study of superconductivity in the Ga-Ag alloy embedded into porous template with pore diameter of 10 nm. The composition was close to the eutectic point in the gallium-rich range. We measured DC and AC magnetizations for temperatures from 1.8 to 10 K and magnetic fields up to 6 T. Three superconducting transitions were found at temperatures 7.05, 6.08, and 2.65 K in contrast to the bulk counterpart. Upper critical field lines were obtained. Activation barriers were evaluated from the AC data. The temperatures of the superconducting transitions were ascribed to emergence of β- and iota-Ga and of an intermetallic different from bulk Ag3Ga2. Keywords: nanostructured Ga-Ag eutectic alloy, superconducting transitions, segregated phases, DC and AC susceptibility.
Electrical and Magnetic Properties of SmSb Single Crystals at Low Temperatures
Authors: Stepanov N.N.  , Kamenskaya G.A.  , Volkov M.P.  , Sharenkova N.V.
Published: January 2023

On SmSb single crystals synthesized from elements, the electrical resistance R and magnetization M were measured as functions of temperature and magnetic field. A large magnetoresistance is observed over the entire temperature range of 2-300 K, increasing significantly with decreasing temperature. The temperature dependence of the magnetization exhibits a singularity at the transition temperature to the antiferromagnetic state TN=2.3 K. At temperatures below 8 K, de Haas--van Alphen oscillations are observed in the M(H) dependences, the frequencies of which do not change upon the transition through TN. Linear extrapolation of the dependence of the Landau indices N on the reciprocal of the magnetic field 1/B to zero gives the value NT=2 K=0.75, which indicates the presence of the Berry phase and a nontrivial band topology in the SmSb compound. Keywords: samarium monoantimonide, magnetization, magnetoresistance, antiferromagnetic phase transition, de Haas-van Alphen magnetic oscillations, Berry phase.
Investigation on Structural, Electronic, Thermal, and Thermoelectric Properties of Co-=SUB=-2-=/SUB=-MnGa under Pressure Based on Density Functional Theory
Authors: Fazeli Kisomi A.  , Mousavi S. J.  , Nedaee-Shakarab B.
Published: January 2023

Structural, electronic, thermal, and thermoelectric properties of Co2MnGa under 0, 5, 10, and 15 GPa pressures have been investigated. In electronic properties, in minority spin, a pseudo band gap (about 0.25 eV) is visible. Thermal properties in the range of 0 to 700 K have been calculated. Our results in thermal properties have a good agreement with another theoretical work. Calculations of thermoelectric properties, in both spin up and down, in the range of 100 to 700 K have been done. In spin up, an abnormal behavior is observed under 5 GPa for electrical conductivity. This is due to increase in Mt at this pressure. The sign and value of Seebeck coefficient in spin up at 300 K has a good consistency with experimental work. Other thermoelectric properties such as: power factor, electronic thermal conductivity divided by relaxation time, electronic contribution of heat capacity at constant volume under pressure have been studied. Keywords: Co2MnGa, density functional theory, electronic properties under pressure, thermoelectric properties under pressure.
Creation of optically addressable spin centers in hexagonal boron nitride by proton irradiation
Authors: Murzakhanov F. F.  , Mumdzhi I. E.  , Mamin G. V.  , Yusupov R. V.  , Davydov V. Yu.  , Smirnov A. N.  , Muzafarova M. V.  , Nagalyuk S. S.  , Soltamov V. A.
Published: January 2023

The possibility of creating defects with spin-dependent fluorescence in a Van der Waals material, hexagonal boron nitride (hBN), by irradiating the latter with high-energy protons (EP=15 MeV) has been studied. Using micro-photoluminescence and electron paramagnetic resonance methods it was shown that such irradiation leads to the creation of boron vacancies in the negative charge state (V-B-centers). The ground spin triplet (S=1) state of these defects demonstrates an optically induced inverse population. Keywords: electron paramagnetic resonance, micro-photoluminescence, hexagonal boron nitride, boron vacancy.
Nonlinear acoustic effects in polycrystalline solids with saturation of amplitude-dependent internal friction
Authors: Nazarov V. E.  , Kiyashko S. B.
Published: January 2023

Theoretical and numerical studies of nonlinear acoustic effects arising from the propagation of initially harmonic waves in polycrystalline solids with saturation of amplitude-dependent internal friction have been carried out. Two main types of hysteresis are considered: elastic and inelastic. A comparative analysis of the regularities of nonlinear effects is carried out and the characteristics of nonlinear quasi-harmonic waves in such media are determined: amplitude-dependent losses and changes in propagation velocity, as well as amplitudes of higher harmonics. A method for determining the type of polycrystal hysteresis based on the analysis of theoretical and experimentally established amplitude dependences of nonlinear effects is proposed. Keywords: elastic waves, amplitude-dependent internal friction.
Autowave Model of an Elastic-Plastic Transition in a Deformable Medium
Authors: Zuev L. B.  , Danilov V. I.
Published: January 2023

The conditions for the generation of autowaves of localized plasticity during the elastic-plastic transition in solids are considered. The similarity and difference between the deformation processes according to the Luders and Portevin--Le Chatelier mechanisms are analyzed and an explanation of these regularities is proposed, based on the introduction of concepts of active deformable media capable of generating switching autowaves and excitation autowaves. The conditions for the formation of such autowaves and the quantitative characteristics of the processes responsible for the transition to plastic deformation are considered. The relationship between the autowave characteristics and the rate of stretching during mechanical tests has been elucidated. Keywords: plasticity, dislocations, autowaves, Luders front, Portevin--Le Chatelier band.
Local magnetic anisotropy in nanostructured FeCo-C coatings synthesized by green chemistry methods
Authors: Denisova E. A.  , Komogortsev S. V.  , Chekanova L. A.  , Neznakhin D. S.  , Iskhakov R. S.  , Nemtsev I. V.
Published: January 2023

Fe-Co alloys attracting interest due to their high magnetic induction and Curie temperature, were synthesized by an eco friendly electroless deposition with carbohydrates as reducing agents. It was shown that Fe1-xCox-C composite coatings retain high induction, while demonstrating an unusual behavior of magnetization at low temperatures. It was found that for each coating measured at different temperatures, there is a correlation between the local magnetic anisotropy constant K at a given temperature and the correlation radius of the local easy magnetization axis Rc. The functional type of this correlation is typical for nanoparticles or nanogranules in a composite, which made it possible to estimate the volume and surface magnetic anisotropy constants of metal granules of FeCo-C coatings. Keywords: magnetic anisotropy, FeCo-C coatings, electroless deposition, approach to magnetic saturation law.
Influence of thermoinduced magnetoelastic effect on domain structure of planar Ni microparticles
Authors: Nurgazizov N. I.  , Bizyaev D. A.  , Bukharaev A. A.  , Chuklanov A. P.  , Shur V. Ya.  , Akhmatkhanov A. R.
Published: January 2023

Results of studying the domain structure of planar Ni microparticles formed on single-crystal substrates from the lithium niobate and from the potassium titanyl phosphate at different temperatures are presented. The dependence of domain sizes on the sample temperature was studied. It is shown the observed change of the domain structure is caused by the magnetoelastic effect, which arises due to the difference in the thermal expansion coefficients of the substrate and microparticles as the sample temperature changes. It is shown, the sizes of magnetic domains, up to the creation of a state with a quasi-homogeneous magnetization may be set by the substrate temperature during the microparticles formation. Keywords: magnetoelastic effect, magnetic force microscopy, remagnetization, lithium niobate, potassium titanyl phosphate, temperature.
Enhancement of magnetocaloric efficiency of Gd spacer between strong ferromagnets
Authors: Pashenkin I. Yu.  , Polushkin N. I.  , Sapozhnikov M. V.  , Demidov E. S.  , Kravtsov E. A.  , Fraerman A. A.
Published: January 2023

The magnetocaloric properties of a thin spacer of gadolinium (Gd) between layers of "strong" ferromagnets (relatively high Curie temperatures) are studied experimentally. It is found that, at room temperatures, the magnetocaloric efficiency Delta S/Delta H (Delta S is the isothermal magnetic entropy change and Delta H is the range of applied magnetic fields) of Gd spacer of thickness of 3 nm is up to two orders in magnitude higher than this value in an individual thicker (30 nm) Gd layer. This opens up opportunities for using the magnetocaloric effect in micro(nano)electronics and biomedicine using relatively weak magnetic fields H<1 kOe. The observed increase in the magnetocaloric efficiency is explained by the influence of direct exchange coupling between Gd spacer and its surroundings, which changes the distribution of magnetization in the spacer and, ultimately, its magnetocaloric potential. Keywords: magnetocaloric effect, magnetic heterostructures, exchange coupling at interfaces, Curie temperature.
Fabrication of High-Quality Josephson Junctions Based on Nb|Al-AlN|NbN
Authors:  Chekushkin A. M.  , Filippenko L. V.  ,  Fominskiy M. Yu.  , Koshelets V. P.
Published: January 2023

A description of the fabrication technology of high-quality tunnel SIS junctions is presented, with following characteristics: energy gap in superconductors Vg=3.2-3.4 mV, tunnel current density up to J 35 kA/cm2, quality factor Rj/Rn (ratio of subgap resistance to normal-state resistance) up to 30, junction area up to 1 μm2. The SIS junctions are integrated into the NbTiN|SiO2|Al microstrip line. Keywords: superconducting devices, superconductor--insulator--superconductor tunnel junction, plasma etching.
Mechanism of domain walls drift in pulsed magnetic fields in iron garnet crystals
Authors: Pamyatnykh L. A.  , Lysov M. S.  , Pamyatnykh S. E.  , Agafonov L. Yu.  , Mekhonoshin D. S.  , Shmatov G. A.
Published: January 2023

Conditions for the drift of domain walls in pulsed magnetic fields of various organization (bipolar and unipolar pulsed magnetic fields, pulse packets) are established. Dependences of domain walls drift velocity on the parameters of pulsed magnetic fields (frequency, amplitude, pulse duration) are obtained. As a result of numerical simulation of domain walls drift in a uniaxial sample, an experimentally confirmed mechanism of domain walls drift in pulsed magnetic fields is proposed. Keywords: pulsed magnetic fields, iron garnets, domain walls, dynamic domain structures, drift of domain walls.
Crystal structure, microstructure, piezoelectric and dielectric properties of high-temperature piezoceramics Bi-=SUB=-3-x-=/SUB=-Nd-=SUB=-x-=/SUB=-Ti-=SUB=-1.5-=/SUB=-W-=SUB=-0.5-=/SUB=-O-=SUB=-9-=/SUB=- (x=0, 0.1, 0.2)
Authors: Zubkov S. V.  , Parinov I. A.  , Nazarenko A. V.  , Kuprina Yu. A.
Published: January 2023

A new series of perovskite-like oxides Bi3-xNdxTi1.5W0.5O9 (x=0, 0.1, 0.2) has been synthesized by the method of high-temperature solid-state reaction. The X-ray diffraction study showed that the compounds are single-phase and have the structure of the family of Aurivillius phases with parameters close to the orthorhombic unit cell corresponding to the space group A21am. The relative permittivity ε/ε0 and loss angle tangent tgsigma are measured as functions of temperature at different frequencies. The piezoelectric modulus d33 was measured for the synthesized compounds. The microstructure of Bi3-xNdxTi1.5W0.5O9 (x=0, 0.1, 0.2) was obtained. The study of the microstructure shows that the crystallites have a shape characteristic of Aurivillius phases. Keywords: Aurivillius phases, Bi2.8Nd0.2Ti1.5W0.5O9, activation energy Ea, Curie temperature TC.
Effect of dopant on piezoelectric and dielectric properties of thin films Bi-=SUB=-3.25-=/SUB=-La-=SUB=-0.75-=/SUB=-Ti-=SUB=-3-x-=/SUB=-A-=SUB=-x-=/SUB=-O-=SUB=-12-=/SUB=- (A --- Mn, Zr, Nb)
Authors: Kiselev D. A.  , Starukhina S. S.  , Ilina T. S.  , Kuharskaya N. F.  , Naryshkina V. G.  , Sivov A. A.  , Chucheva G. V.
Published: January 2023

It is shown that microstructure, dielectric and piezoelectric properties change in films based on lanthanum-substituted bismuth titanate (BLT) depending on the alloying impurity material, which leads to changes in coercive voltage, internal displacement field and control coefficient. Keywords: lead-free ferroelectric films, bismuth titanate, electrophysical properties, capacitance-voltage characteristics, piezoresponse force microscopy.
Semiconductor-metal phase transition in oxides of Magneli series: VO and V-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-
Authors: Ilinskiy A. V.  , Shadrin E. B.
Published: January 2023

A comparative analysis of the physical parameters of strongly correlated oxides VO and V2O3 has been carried out. It has been established that the semiconductor--metal phase transition in both VO and V2O3 has a complex Mott-Peierls character. Namely, as the temperature increases in both oxides, before the Peierls abrupt structural phase transition, the Mott phase transition, which is extended in temperature, take place. It has been discussed the reason for the fact that, despite the stabilization of the semiconductor phase by high-strength π-dimers or sigma-dimers, the temperatures of phase transitions are low (Tc=126 K (VO) and Tc=140 K (V2O3)). Keywords: Magnelis series, phase transformations, electron-electron correlations.
Ab initio calculation of the band structure and properties of modifications of the Ti-=SUB=-3-=/SUB=-Sb compound doped with lithium
Authors: Asadov M.M.  , Mammadova S.O.  , Huseinova S.S.  , Mustafaeva S.N.  , Lukichev V.F.
Published: January 2023

Using the density functional theory (DFT) in the local electron spin density approximation (LSDA), 2x2x2 supercells based on the Ti3Sb compound have been studied. The supercells contained their own vacancies and doped lithium atoms replacing Ti and/or Sb. The DFT-LSDA method was used to calculate the structural, electronic, and magnetic properties, the enthalpy of formation, and the cohesion energy of supercells of two modifications of the Ti3Sb compound. We studied supercells with cubic system (A15 type structure; a=5.217 Angstrem) and tetragonal system (D8m type structure; a=10.457 Angstrem, c=5.258 Angstrem). It has been established that the distribution of the density of states of the Ti3Sb cubic system has a more metallic character than for the D8m Ti3Sb modification. The enhancement of "metallicity" in the cubic modification A15 Ti3Sb is associated with an increase in the Ti-Sb interatomic distance in the crystal. Due to this, the degree of metallic bonding increases during the electronic interaction between Ti and Sb atoms near the Fermi level in Ti3Sb. In DFT calculations, the spin-polarized density of states was taken into account. It has been established that in both modifications (A15 and D8m) of Ti3Sb near the Fermi level for s-, p-, d-states with spin "up" and spin "down" there is a spin imbalance in the population of energy levels. Defect-containing supercells based on Ti3Sb were studied by DFT-LSDA calculations. It is shown that Ti and/or Sb vacancies in the lattices of Ti3Sb crystals of both modifications (A15 and D8m) increase the magnetic moment (M) as compared to the value of M (M=0.08 μB) of a "pure" Ti3Sb crystal. Considering that Al5 Ti3Sb is also interesting as a material for Li-ion batteries, we studied Ti3Sb-Li supercells doped with lithium. Li-doping and the creation of own Ti and/or Sb vacancies changes the distance between atoms in Ti3Sb. Correspondingly, the resulting local magnetic moments near the Ti or Sb vacancies also change. The enthalpy of formation and magnetic moment of Ti3Sb and Ti3Sb-Li based supercells are calculated. DFT calculations of the structural stability of binary compounds (phases) have been carried out, and the stability of conodes between phases in the Ti-Sb-Li system has been established. The isothermal section of the Ti-Sb-Li system was plotted at 298 K. It is shown that the introduction of various lithium concentrations (≤6.25 at.% Li) into the Ti3Sb (Space group Pm3 n; N 223; a=5.217 Angstrem) crystal lattice reduces the partial magnetic moment of Ti in the Ti3Sb-Li supercell. Keywords: Ti3Sb intermetallic compounds, A15 cubic modification, D8m tetragonal modification, doping with lithium, Ti3Sb-Li, DFT-LSDA calculations, supercell, electronic and magnetic properties, Ti-Sb-Li phase stability.
Phase transformations in barium-strontium niobate SBN-50 in the temperature range from 80 K to 700 K according to Raman spectroscopy data
Authors: Matyash Ya. Yu.  , Anokhin A. S.  , Pavlenko A. V.
Published: January 2023

The lattice dynamics of the Sr0.5Ba0.5Nb2O6 (SBN-50) ceramic was studied using Raman spectroscopy in the temperature range of 80-700 K with a step of 10 K. The analysis of the Raman spectra in the range ν=50-1000 cm-1 revealed features in the temperature dependence behavior of the optical modes frequencies associated with the displacement of Ba, Sr and Nb atoms from their average positions in the crystal lattice, which is associated with a macroscopic phase transition from the paraelectric to the ferroelectric phase in the vicinity of 390 K. It is shown that anomalies at T~565 K on the temperature dependences of the frequency and line half-width corresponding to the oscillations of the NbO6 octahedron can be caused by the presence of polar nanoregions in the paraelectric phase in SBN-50. When the sample was cooled to a temperature of 80 K, the behavior was recorded in the Raman spectra, indicating the occurrence of a structural phase transition in the ferroelectric phase in the vicinity of 190 K. The reasons for the revealed patterns are discussed. Keywords: ferroelectric, Raman scattering, SBN, tetragonal tungsten bronze.
Structural and phase features of zinc selenide nanoparticles obtained by laser evaporation
Authors: Murzakaev A. M.  , Osipov V. V.  , Platonov V. V.
Published: January 2023

The first production of weakly agglomerated zinc selenide nanopowders by evaporation of a target of the required chemical composition in argon using a fiber ytterbium laser is reported. Nanoparticles have the shape of polyhedrons and, more rarely, spheres with an average size of 18 nm. According to XRD data, the obtained nanopowders contain two phases: a stable cubic phase (sphalerite, 40 wt.%) and a metastable hexagonal phase (wurtzite, 60 wt.%). An analysis of HRTEM showed that most of the nanoparticles have structural defects. Due to superstoichiometry, defects in the crystal structure of the crystallographic shift type are formed in nanoparticles. Magneli phases, Wadsley defects and various kinds of heterogeneity inside the particles were found. Keywords: Laser evaporation, zinc selenide, nanoparticles, high resolution transmission electron microscopy (HRTEM), defects, phase composition, crystallographic shift, Magnelli phase, Wadsley defects.
Interface doping of zinc oxide nanorods
Authors: Ryabko A. A.  , Mazing D.S.  , Bobkov A. A.  , Maximov A. I.  , Levitskii V. S.  , Lazneva E. F.  , Komolov A. S.  , Moshnikov V. A.  , Terukov E. I.
Published: January 2023

The effect of an increase in the electrical conductivity of a system of zinc oxide nanorods by a factor of 105 during atomic layer deposition of a thin dielectric layer of aluminum oxide was found. It is shown that a change in the electrical conductivity of zinc oxide during atomic layer deposition of aluminum oxide on the surface is also observed for thin polycrystalline layers of zinc oxide. A study of polycrystalline layers of zinc oxide coated with aluminum oxide using ultraviolet and X-ray photoelectron spectroscopy is presented. Based on the results of photoelectron spectroscopy, two main factors for changing the electrical conductivity are proposed, which consist in the formation of a two-dimensional electron gas at the ZnO|Al2O3 interface and doping of the near-surface region of zinc oxide with aluminum atoms. Keywords: nanorods, zinc oxide, aluminum oxide, atomic layer deposition, transparent electrodes, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy.
Percolation effect impact on resistive switching of structures based on nanocomposite (Co-=SUB=-40-=/SUB=-Fe-=SUB=-40-=/SUB=-B-=SUB=-20-=/SUB=-)-=SUB=-x-=/SUB=-(LiNbO-=SUB=-3-=/SUB=-)-=SUB=-100-x-=/SUB=-
Authors: Nikiruy K.E.  , Emelyanov A.V.  , Matsukatova A.N.  , Kukueva E.V.  , Vasiliev A.L.  , Sitnikov A.V.  , Demin V.A.  , Rylkov V.V.
Published: January 2023

Comparative studies of resistive switching (RS) effect of metal/nanocomposite/metal (M/NC/M), metal/nanocomposite/LiNbO3/metal (M/NC/LNO/M) structures based on NC (Co40Fe40B20)x(LiNbO3)100-x (x=6-20 at.%) with CoFe nanogranules 2-4 nm in size, as well as structures without a NC layer (M/LNO/M), have been carried out. It was found that the percolation conductivity in NC and presence of a thin LNO layer play a key role in the RS effect. When the metal content approaches the percolation threshold of M/NC/M structures (xp~10 at.%), low-resistance percolation nanochannels of granules are formed in structures with an embedded LNO layer, which ensure their stable RS, which, however, are noticeably suppressed as x decreases relative to xp by Delta x~1-2 at.%. Keywords: resistive switching, memristor, nanocomposite, percolation.
Magnetocaloric effect in Gd microwires
Authors: Koplak O. V.  , Kashin S. N.  , Morgunov R. B.  , Korolev D. V.  , Zhidkov M. V.  , Piskorsky V. P.  , Valeev R. A.
Published: January 2023

In Gd microwires obtained by ultrafast cooling of the melt, a change in the magnetic entropy of 12 J/kg K was determined at a Curie temperature of 293 K in a magnetic field of 5 T. This value coincides with the change in the magnetic part of the entropy in bulk single-crystal samples in the same field. It has been found that in a strong magnetic field of 9 T, the temperature dependence of the entropy exhibits two maxima at temperatures of 292 and 312 K. The appearance of an additional entropy maximum in microstructured samples is caused by high mechanical microstresses retained in the sample after ultrafast cooling. Keywords: microwires, magnetic entropy, magnetoelastic anisotropy, Curie temperature.
Thermomechanics and statistical mechanics of an adiabatically isolated body
Authors: Gorobey N. N.  , Lukyanenko A. S.  , Goltsev A. V.
Published: January 2023

A statistical distribution for an adiabatically isolated body is proposed and its temperature is defined as a function of a given energy. It is obtained as a result of the generalization of the statistical distribution for an ensemble of oscillators, in which the probability is proportional to the time of motion on each small section of the oscillator trajectory in the phase space. This distribution makes it possible to explain the thermoelastic effect --- the dependence of the body temperature on the deformation under its adiabatic mechanical loading. The proposed explanation is in clear agreement with the first law of thermodynamics. Keywords: adiabatic, thermoelastic effect, statistical distribution, partition function, temperature.
Effect of interlayer coupling on the electron spectra of vertical superlattice
Authors: Davydov S. Yu.
Published: January 2023

By use of the Green's function method analytical expressions for the dispersion lows of superlattice (SL) consists of two alternating 2D layers are obtained. Weak interlayer coupling regime is analized thoroughly. As the examples, the SLs graphene --- h-BN ( 1), AlN --- GaN ( 2), Gr --- Ni ( 3) and h-BN --- Ni ( 4) are considered and analytical electron spectrum characteristics for the corresponding 2D layers are given. It is shown that 1) electron effective masses become havier for the h-BN, AlN, GaN, and Ni layers in all SLs; 2) Fermi velocity becomes lower for the gapless graphene layer in the SL ( 1) and remains constant in the SL ( 3); 3) energy gaps become narrower for the h-BN, AlN and GaN layers in the SLs (1) and ( 2) and wider for h-BN layer in the SL (4). Keywords: dispersion low, Fermi velocity, effective mass, graphene-like compound, two-dimensional ferromagnetic metal.
Unoccupied electronic states of ultrathin phenolphthalein films on the ZnO surface formed by atomic layer deposition
Authors: Komolov A.S.  , Lazneva E.F.  , Gerasimova N.B.  , Sobolev V.S.  , Zhizhin E.V.  , Pudikov D.A.  , Sodylev R.  , Pshenichnyuk S.A.  , Asfandiarov N.L.  , Handke
Published: January 2023

The results of a study of the unoccupied electronic states of ultrathin films of phenolphthalein molecules on a ZnO surface formed by atomic layer deposition technique are presented. The atomic composition of the ZnO layer was determined by X-ray photoelectron spectroscopy (XPS) and its crystallinity was characterized using X-ray diffraction. The predominance of the content of O atoms by 5-10%, compared with the content of Zn atoms, was found. The electronic characteristics of the ZnO/phenolphthalein structure were studied using total current spectroscopy (TCS) in the energy range from 5 eV to 20 eV above EF during thermal vacuum deposition of phenolphthalein films up to 8 nm thick. Phenolphthalein molecules contain two hydroxyl functional groups. The TCS results on the phenolphthalein films are compared with the TCS results obtained from films of molecules that represent the backbone of phenolphthalein molecules without hydroxyl groups. The TCS fine structure maxima of phenolphthalein films located in the energy range from 5 eV to 8 eV above EF can be associated with the boundaries of the π* bands of electronic states. The work function of the ZnO surface formed by the ALD method were 4.2±0.1 eV. The deposition of a phenolphthalein film led to a decrease in the work function of the surface by 0.1 eV. Keywords: Phenolphthalein, ultrathin films, ZnO, atomic layer deposition, electronic properties, low-energy electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy.
Electronic Structure of Dimers Based on C-=SUB=-58-=/SUB=- Fullerene Isomers as Structural Elements of Films on the Au Surface
Authors: Murzashev A. I.  , Zhumanazarov A. P.
Published: January 2023

Within the framework of the Hubbard model, the energy spectra of the Cs and C3v isomers of C58 fullerene and dimers based on them are calculated. The obtained curves of the density of electronic states of these systems are compared with the experimental curves of the films, which were obtained by deposition of the Cs and C3v isomers of C58 fullerene on the (1,1,1) gold surface. A comparative analysis of the curves of the density of electronic states shows that in those sites through which a bond is formed between fullerenes, carbon is not in the sp2, but in the sp3 hybridized state. Keywords: fullerene, dimer, energy spectrum, Hubbard model, Hubbard subband, density of electronic states.
Electronic band structure and thermoelectric properties of SrTiO-=SUB=-3-=/SUB=-, BaTiO-=SUB=-3-=/SUB=- and CaTiO-=SUB=-3-=/SUB=-: ab initio approach
Authors: Zhukov V. P.  , Chulkov E. V.
Published: January 2023

The calculations of Seebeck's coefficient, conductivity and power functions for the electron-doped SrTiO3, BaTiO3 and CaTiO3 compounds have been performed depending on temperature and current carrier concentration by employing ab initio method based on the electron density functional theory, on the Frohlich's approach for the electron-phonon interaction and on the theory of Boltzmann--Onsager for the thermoelectric properties. The calculated Seebeck's coefficient and conductivity correspond to experimental data. It is shown that for SrTiO3 and BaTiO3 the dependencies of power functions on the carrier concentration have maxima in the range of (200-250)·1019 cm-3 at any temperature, while for CaTiO3 the maxima are typical only at temperatures below 500 K. The temperature dependencies of the power function also confirm that such carrier concentration range is favorable for achieving high values of the SrTiO3 figure of merit, while the maximally possible carrier concentration is necessary for optimal CaTiO3 figure of merit. Keywords: Ca, Sr, Ba titanates, PAW method, electronic structure, thermoelectric properties.
Electrical conductivity and structural conditionality of ion transfer in langasite La-=SUB=-3-=/SUB=-Ga-=SUB=-5-=/SUB=-SiO-=SUB=-14-=/SUB=-:Mn
Authors: Sorokin N. I.  , Golovina T. G.  , Konstantinova A. F.
Published: January 2023

The temperature dependence of the static electrical conductivity sigmadc(T) of a single crystal of lanthanum gallium silicate (langasite) La3Ga5SiO14 activated with an impurity of Mn (1000 ppm) has been studied by impedance spectroscopy. Impedance measurements of La3Ga5SiO14 (sp. gr. P321, Z=1) were carried out along crystallographic axes a (double symmetry axis) and c (triple symmetry axis). It was found that the values of sigma|| a are significantly higher than the electrical conductivity sigma|| c, the anisotropy of the electrical conductivity is sigma|| a/sigma|| c=170 at 773 K. The activation energy of electrotransport is Esigma=0.75±0.05 and 1.09±0.02 eV along the a and c axes, respectively. The electrical conductivity mechanism has an ionic nature and an impurity character; oxygen vacancies VOoo are the most probable current carriers. Keywords: lanthanum gallium silicate, langasite family, single crystal, electrical conductivity, anisotropy.
Specificity of the Transformation of End Methyl Groups in the Interlamellar Regions of Tetracosane during the Solid-Solid Phase Transition as revealed by FTIR Spectroscopy
Authors: Marikhin V. A.  , Gureva S. A.  , Vlasova E. N.
Published: January 2023

The kinetics of the development of the first-order diffuse structural phase transition in monodisperse samples of tetracosane C24H50 was studied by FTIR spectroscopy. The temperature dependences of the frequencies and intensities of the C-H-stretching vibrations in the spectral region ν=2800-3000 cm-1 were studied for 4 different modes in the methylene CH2 trans sequences of the main chain and for 4 different modes corresponding to the end methyl CH3-groups. Specific changes in the vibrational frequencies of all investigated modes are found, which are caused by changes in the symmetry of the molecular packing during the first-order phase transition. Keywords: n-alkanes, phase transitions, theory of diffuse phase transitions, IR spectroscopy.
Investigation of Polyvinyl Alcohol-CuS Compound with Metal-Like Conductivity
Authors: Prosanov I. Yu.  , Romanenko  A. I.  , Chebanova G. E.
Published: January 2023

PVA-CuS compound produced from hybrid interpolymeric polyvinyl alcohol (PVA)-CuCl2 complex through solid state sulfurization was investigated by means of X-ray diffraction, UV-Vis and Raman spectroscopy, and direct current measurements. It is claimed that CuS in this compound has one-dimensional structure. This result is achieved by using a precursor technique based on diffusion limitation at solid state synthesis, so that the structure of initial reagents is inherited by reaction products. The produced material is determined to possess metal-type conductivity and thermopower in the vicinity of room temperature. Keywords: hybrid interpolymeric complexes, polyvinyl alcohol, CuS, inorganic polymers, one-dimensional structures, electrical properties.