bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption of oxygen and hydrogen on monocrystalline tungsten surface at low temperatures (down to 5 K)
Authors: Osovskii V. D. , Ptushinskii Yu. G. , Sukretnyi V. G. , Chuikov B. A.
Published: January 2025

Adsorption of oxygen and hydrogen at monocrystalline tungsten surfaces of various orientations is studied at low temperatures down to 5 K by using molecular beam and thermodesorption (TD) spectroscopy techniques in a set-up of the type of a “black” chamber. Irrespective of the surface orientation, the low-temperature TD spectra of the molecular states of oxygen contain three peaks at 25, 27, and 45 K corresponding respectively to multilayer condensation, physical adsorption, and weak molecular chemisorption. A model of layered growth of oxygen cryocrystals is proposed by taking into account the earlier data on the formation of an atomic adsorption state in the first monolayer. Low-temperature TD spectra of molecular states of hydrogen are found to be different for different surface orientations: two peaks are observed at 8 and 60 K for W(110), while only one peak at 8 K is observed for W (111). Dissociative chemisorption during formation of the first monolayer right down to 5 K, which corresponds to a very low height of the activation barrier (≲ 10 meV), is a common feature of oxygen and hydrogen adsorption at all the investigated surfaces. This regularity is violated only in the case of hydrogen adsorption by W(110), when a molecular adsorption state with a desorption temperature 60 K begins to be formed simultaneously with the state of atomic adsorption from the zeroth layer. Investigations of the dependence of the oxygen and hydrogen sticking probability on the extent of covering, substrate temperature, and the kinetic energy of incident molecules revealed various absorption mechanisms with and without the precursor stage.
Low-temperature desorption of solid argon stimulated by hot excitons
Authors: Savchenko E. V. , Fugol’ I. Ya. , Grigorashchenko O. N. , Gubin S. A. , Ogurtsov A. N.
Published: January 2025

Exciton-stimulated desorption of excited argon atoms is studied by using luminescence VUV spectroscopy. The channels of desorption associated with self-trapping of surface excitons and self-trapping of bulk excitons in the surface region of the crystal are analyzed. It is shown that the nonthermalized excitons play the major role in the transport of excitation energy to the surface.
Processes stimulated by exciton localization in oxygen–neon solid solutions
Authors: Belov A. G. , Fugol’ I. Ya. , Yurtaeva E. M.
Published: January 2025

Processes stimulated by localization of excitons in the neon matrix at O2 and Xe impurity centers are investigated by cathode luminescence spectroscopy. It was found that (1) the trapping of electron excitations of the matrix by O2 molecules leads to effective dissociation; (2) the excitation of O and Xe impurity atoms causes an accelerated migration of these atoms over the crystal and exciton-stimulated desorption of O*; (3) defects are formed in the vicinity of impurity centers; and (4) XeO* excimer compounds are formed in Ne–O2–Xe solutions. The mechanisms of these processes associated with the transfer of the electron excitation energy of the matrix to the impurity subsystem and with its subsequent relaxation are considered.
On the possible nature of the linear low-temperature contribution to the heat capacity of fullerite C60
Authors: Ivanov M. A. , Loktev V. M
Published: January 2025

A mechanism of glass-like behavior of the heat capacity of pure fullerite is proposed and discussed. The mechanism is based on the assumption of orientational intermolecular disorder in the crystal and on the multilevel nature of the C60 molecular spectrum in a crystal field.
Magnetic response of an YBCO film supporting an alternating current
Authors: Grishin A. M. , Drobot’ko V. F. , Mazaev A. A. , Stasovskii V. D. , Khoklov V. A.
Published: January 2025

A nonlinear induction of magnetic field by alternating current has been experimentally discovered in an YBCO film. The film was loaded with a transport current of frequency 10 kHz and amplitude from 0.25 to 7 mA. The maximum transport current density was 88 A/m2. The emf was measured in a flat coil pressed to the surface of the superconducting film. The observed nonlinear signal is shown to be a superposition of two effects, viz., the Meissner screening of the induced magnetic signal and the emf due to the electric field of the current flowing through the film. In the vicinity of the resistive transition temperature TR = 0, nonlinearity reaches its maximum. The signal spectrum contains, along with odd harmonics, higher even harmonics.
Josephson and quasi-particle currents in partially dielectrized superconductors with spin density waves
Authors: Gabovich A. M.
Published: January 2025

Current–voltage characteristics of non-steady Josephson current are calculated for SD–I–SD and SD–I–S tunnel junctions. Here S denotes a standard BCS superconductor; I, insulator; SD, superconductor with part of the Fermi surface developing a spin-triplet dielectric gap Σ at a temperature TN > Tc (Tc being the superconducting transition critical temperature) which is accompanied by appearance of a spin density wave. The I–V curves features a number of Riedel-type logarithmic singularities and steps whose position is determined by the gap Σ and the superconducting energy gap Δ. The results obtained can be tested on tunnel junctions that involve antiferromagnetic superconductors such as Cr1–xRex, URu2Si2, YBa2Cu3O6.55 and others.
Fluctuation-induced discontinuous phase transition in the magnetic subsystem of La2CuO4
Authors: Ivanchenko Yu. M. , Filippov A. É. , Radievskii A. V.
Published: January 2025

We report a theoretical investigation of the critical behavior of the magnetic subsystem in the high-Tc compound La2CuO4. Our attention is mainly directed to the relation between theoretical results and experiment.
Effect of pulsed microwave irradiation on electrical and magnetic properties of HTSC ceramic ErBa2Cu3Ox
Authors: Andreevskii K. N. , Biryukova E. A. , Kortkhonjiya V. P. , Manjavidze A. G. , Rustambekov A. V. , Sobolevskaya S. V. , Shilo S. I.
Published: January 2025

The effect of pulsed microwave irradiation on electrical and magnetic properties of the ErBa2Cu3Ox ceramic with 1-2-3 structure was studied. The behavior of the resistance as well as of the real (χ′) and imaginary (χ″) parts of the dynamic magnetic susceptibility as functions of temperature indicates that irradiation of the ceramics with moderate doses (40 to 60 pulses) results in Tc shifting to higher temperatures (from 0.92 to 93.5 K); increasing the dose leads to a less marked growth or even to a decrease of Tc as compared to non-irradiated material. After a six-month interval, the Tc in irradiated ceramics shifts additionally to approximately the same value of 93.7 or 94.0 K whereas subsequent annealing at 450 °C, to a reverse shift of Tc to lower temperatures down to values less than in the initial (non-irradiated) material.
Zero-sound velocity in gallium
Authors: Bezuglyi E. V. , Burma N. G. , Deineka E. Yu. , Fil’ V. D.
Published: January 2025

The electron sound velocity ν0 in gallium under weak relaxation conditions and the spectrum of Fermi velocities νF are measured. The value of ν0 coincides with νFmax to within experimental errors in accordance with the hypothesis on the Fermi-liquid origin of electron sound signals. The effect of electron scattering on ν0 is investigated theoretically and experimentally. It is shown that, under strong relaxation, the electron sound is transformed into a concentration mode, i.e., a sort of analog of first sound.
Anisotropic size effects in bismuth-type semimetals
Authors: Korshak A. N.
Published: January 2025

A theory of anisotropic size effects (ASE) in pure bulk single crystals of bismuth-type semimetals at helium temperatures in arbitrary magnetic fields is constructed. The model of three-electron and one-hole valley is used for deriving expressions for transverse quasi-Hall electric field, magnetoconductivity, magnetothermoelectric power of phonon drag, and transverse Nernst–Ettingshausen effect. Quantum oscillations of kinetic coefficients of semimetals induced by ASE are investigated. It is shown that the temperature dependence of the amplitude of these oscillations distinguishes them from the Shubnikov–de Haas and magnetophonon resonance oscillations. The oscillations of transverse magnetoresistance and longitudinal thermoelectric power of phonon drag in compensated materials are found to be giant.
Calculated optical properties of heavy metals. I. Relativistic formalism and cubic 5d metals
Authors: Antonov V. N. , Bagljuk A. I. , Perlov A. Ya. , Nemoshkalenko V. V. , Antonov VI. N. , Andersen O. K. , Jepsen O.
Published: January 2025

The formalism for calculation of the optical properties of solids within the random phase approximation and the relativistic linear muffin-tin-orbital method is presented. The method is applied to the cubic 5d metals Ta, W, Ir, Pt, and Au using the local density approximation. The band structures, the lj projected densities of states, the complex dielectric functions, the optical conductivities, and the electron energy-loss spectra are evaluated in the energy range from 0 to 30 eV. Good agreement with the experimental data is found.
Quantum-size oscillations in Mo/Si superlattices
Authors: Bukhshtab E. I. , Kashirin V. Yu. , Fogel’ N. Ya. , Cherkasova V. G. , Kondratenko V. V. , Fedorenko A. I. , Yulin S. A.
Published: January 2025

Oscillatory dependences of a number of kinetic and superconducting characteristics on the superstructure period D have been observed in superconducting Mo/Si superlattices with a constant thickness (25 Å) of silicon interlayers and a variable thickness (from 8 to 200 Å) of the metal layers. The position of the extrema on the dependences Tc(D) of the superconducting transition temperature, ρn(D) of resistivity, and ρ300/ρn(D) of the resistivity ratio, as well as the derivative dHc⊥/dTTc of the transverse critical field with respect to temperature are strictly periodic (Δd = 35 Å). The observed oscillations are associated with the quantum size effect which has been observed so far only in solitary thin layers of metals and semimetals. The oscillation period of 35 Å slightly exceeds the value expected from the data on the electron spectrum of bulk molybdenum. This may be due to a change in the band structure as a result of a strong disordering of Mo in thin layers, as well as to the interaction between layers. This interaction is also manifested in the 3D–2D crossover on the Hc∥(T) dependence. Samples of Mo/Si superlattice simultaneously exhibit two- and three-dimensional behavior in different physical properties.
Creep studies in subkelvin temperature range: experiments on zinc single crystals on a new setup
Authors: Kalugin M. M. , Natsik V. D. , Soldatov V. P. , Shepel’ I. A.
Published: January 2025

An experimental setup with a cryostat based on a 3He evaporation refrigerator for studying creep of solids in the temperature range T > 0.5 K is described. First results are presented on the laws governing the creep of zinc single crystals deformed by pure shear along the basal plane in the temperature interval 0.5–1.0 K.
Effect of HTS cathode on electric discharge in vacuum
Authors: Mikhalyuk N. I. , Palatnik L. S. , Sokolov Yu. V.
Published: January 2025

Electric discharge in vacuum between an HTS cathode (a ceramic with composition YBa2Cu3O7–δ) and a normal metal (tungsten) is investigated. It is shown that the flash electron emission produced from an HTS cathode has a number of peculiarities. Cooling to temperatures below the critical value sharply increases the discharge current and breakdown voltage (which remains much lower than for metallic cathodes). The duration of the discharge is prolonged considerably and this results in an intensive flash evaporation of the anode at the arc stage of the discharge. A comparative analysis is made for the typical characteristics of the electric breakdown in the case of an HTS cathode in superconducting and normal states, as well as for metal cathodes.
Thermodynamic properties of fullerene-60
Authors: Yakub L. N.
Published: January 2025

The equation of state proposed earlier for solidified inert gases has been modified and used for calculating the thermodynamic properties of solid fullerene C60. The density, isothermal compressibility, thermal pressure, and volume expansion coefficient have been calculated in the temperature range 250–1000 K.
Temperature dependence of the energy gap in the one-particle spectrum of layered semiconductors
Authors: Davydov A. S. , Ermakov V. N.
Published: January 2025

The temperature dependence of the superconducting gap is calculated in the bisoliton theory of HTS. It is shown that if thermal vibrations of lattice atoms are taken into consideration, the ratio of the superconducting gap to the critical temperature increases, and may considerably exceed the value given by the BCS theory. This conclusion is in agreement with the experimental results.
EPR and estimation of the dipole–dipole interaction energy in KEr(MoO4)2
Authors: Anders A. G. , Volotskii S. V. , Zubkov O. É.
Published: January 2025

The EPR spectrum of KEr(MoO4)2 is investigated. The values of effective g-factors are calculated for the ground and first excited doublets. The obtained results are used to estimate the dipole–dipole interaction energy in the chain of rare-earth ions.
Peculiarities of the critical behavior of conductivity in cold-deposited sodium–ammonia films
Authors: Moshenskii A. A. , Spasova M. A.
Published: January 2025

Metal–nonmetal transition has been studied in cold-deposited sodium–ammonia thin films upon a decrease in the metal concentration. It is found that the critical conductivity index just after condensation is 3 ± 0.1. This is a new and unexpected result. Annealing of the system results in a gradual decrease in the critical conductivity index to a value close to 2, which is characteristic of the classical percolation case. The experimental data are compared with the results obtained from theoretical models describing the behavior of the critical indices in different systems.
On the theory of quantum galvanomagnetic effects in two-dimensional systems with strong electron–electron correlations
Authors: Monarkha Yu. P.
Published: January 2025

Formulas connecting the magnetoconductivity tensor with the dynamic structural factor of a two-dimensional electron liquid have been obtained for an arbitrary relation between the cyclotron frequency ωc and the magnetic field-dependent collision frequency ν. It is shown that in many cases, e.g., in the case of electrons at the free surface of liquid helium, the collision frequency ν increases with magnetic field in a wide range of values of the external parameters more rapidly than the cyclotron frequency. This makes it impossible to use the results of theories based on the approximation ωc ≫ ν in the ultraquantum region.
Dimension crossover and the nature of the superconducting layers in PbTe/PbS semiconductor superlattices
Authors: Dmitrenko I. M. , Fogel’ N. Ya. , Cherkasova V. G. , Fedorenko A. I. , Sipatov A. Yu.
Published: January 2025

We studied resistive transitions in magnetic fields on superconducting PbTe/PbS multilayers with different superstructure periods, from which parallel and perpendicular critical magnetic fields have been determined. In fields parallel to the layer plane we observe sharp changes in the behavior of Hc2‖ as a function of temperature, which suggests the existence of a 3D–2D dimensional crossover. A double dimensional crossover is found on samples of finite thickness with a small number of periods. For all the superlattices, the superstructure period, as calculated from superconducting characteristics, corresponds to the half-period measured by x-ray diffraction. We have thus proved that superlattices are responsible for superconductivity in PbTe/PbS layers situated at the interface between two semiconductors and containing regular networks of misfit dislocations. This conclusion is also confirmed by data on the double dimensional crossover. The superconducting layer thickness evaluated on the basis of experimental data correlates for all samples with the superstructure period. It has been established that the strong smearing of resistive transitions, similar to that in single-crystal high-Tc. superconductors, does not prevent correct determination of superlattice parameters. It is shown that semiconductor PbTe/PbS superlattices can serve as a good testing ground, for modeling the properties of HTSC.
Calculated optical properties of heavy metals. II. Hcp 5d metals
Authors: Antonov V. N. , Bagljuk A. I. , Perlov A. Ya. , Nemoshkalenko V. V. , Antonov VI. N. , Andersen O. K. , Jepsen O.
Published: January 2025

The relativistic self-consistent LMTO method was used to calculate the optical properties of the hep 5d metals Hf, Re and Os. The complex dielectric function, optical conductivity and electron energy loss spectra were calculated in the energy range from 0 to 30 eV for the two polarizations of the electromagnetic field e ‖ c and e ⊥ c. The calculated spectra are in a good agreement with available experimental data.
Calculated optical properties of heavy metals. III. Actinides
Authors: Antonov V. N. , Bagljuk A. I. , Perlov A. Ya. , Nemoshkalenko V. V. , Antonov VI. N. , Andersen O. K. , Jepsen O.
Published: January 2025

The relativistic self-consistent LMTO method has been used to calculate the optical properties of the actinides Ac, Th, Pa, U, Np and Pu. The complex dielectric function, optical conductivity and electron energy loss spectra were calculated in the energy range from 0 to 25 eV. The theoretical results are compared with available experimental data.
Quantum galvanomagnetic effects in metal plates in a weak transverse magnetic field due to multichannel specular reflection of electrons
Authors: Slutskin A. A. , Manzhelii E. V.
Published: January 2025

A new class of quantum interference (QI) kinetic size effects in metals is described. These effects emerge as a result of multichannel specular reflection (MSR) of electrons at the boundaries of a metal plate of thickness L ≲ l0 (l0 is the electron mean free path) placed in a weak transverse magnetic field of strength H ≲ HL = ℏc/eL2 (e is the electron charge and c the velocity of light). The influence of such a weak field on MSR dynamics of electrons is confined simply to its effects on the quasiclassical phases of Bloch functions of various MSR channels. A consistent theory is developed for the galvanomagnetic QI phenomena which can be described in terms of the effective dynamics of the above phases that can be used as independent “classical” variables. It is shown that the components of the conductivity tensor of the plate in a field H ∼ H0 ∼ cℏ/el0L vary by an amount comparable with the characteristic conductivity of the plate and tend to a universal asymptotic behavior for HL ≳ H ≫ H0.The QI effect of electron localization by a weak transverse field of strength H < HL is predicted. The frequency ωq of precession in such quantum “traps” turns out to be anomalously high: ωq ∼ (pFL/ℏ) ωc ≫ ωc (pF is the Fermi momentum and ωc the characteristic Larmor frequency). It is shown that the above effects can be observed quite easily experimentally.
Thermo-emf of the superconducting ceramic YBa2Cu4O8 under hydrostatic pressure up to 10 kbar
Authors: Kraidenov V. F. , Itskevich E. S.
Published: January 2025

The temperature dependence of the thermo-emf α of the ceramic YBa2Cu4O8 has been measured in the temperature range 4.2–300 K under hydrostatic pressure up to 10 kbar. It is found that α is positive for all values of T and P, has a minimum at T ≈ 150 K and a superconducting transition temperature Tc ≈ 80 K. The pressure causes a sharp decrease in α and an increase in Tc: d In α/dP = –4 · 10−5 kbar−1, dTc/dP = 0.48 K/kbar. Such a strong dependence of α and Tc on P was earlier observed in oxygen-deficient ceramics YBa2Cu3Ox (x = 6.5–6.6).
Absence of metal–insulator transition in Hubbard’s model for a hypercubic lattice
Authors: Alistratov A. L. , Dimashko Yu. A. , Podol’skii V. S.
Published: January 2025

Hubbard’s model with local repulsion and half-filled band is considered for a hypercubic lattice. It is shown that there is no metal–insulator transition in this model and its ground state is an antiferromagnetic insulator for any finite interaction.
On the damping of quasifiexural waves in layered conductors
Authors: Gokhfel’d V. M. , Panchenko O. F.
Published: January 2025

The contribution of charge carriers to the absorption of quasifiexural elastic waves in conducting layered crystals is calculated. It is shown that the quadratic energy-momentum relation for such waves together with the quasi-two-dimensional nature of the electron energy spectrum of layered conductors leads to an unusual frequency dependence of the absorption coefficient.
Noncollinear multisublattice magnetic structure of the quasi-two-dimensional antiferromagnet NH3(CH2)2NH3MnCl4
Authors: Eremenko V. V. , Kachur I. S. , Piryatinskaya V. G. , Shapiro V. V.
Published: January 2025

The exciton spectrum of light absorption in a magnetic field is investigated in NH3(CH2)2NH3MnCl4. It is found that the unit cell of NH3(CH2)2NH3MnCl4 contains four structural units. It is also shown that its magnetic structure is noncollinear in the absence of a magnetic field.
Paramagnetic susceptibility and magnetic flux creep in the YBa2Cu3Ox ceramic: variation with sample thickness
Authors: Tsymbal L. T. , Cherkasov A. N. , Volkova L. P. , Kudryashova S. N.
Published: January 2025

The inter-granular losses in diamagnetic susceptibility were studied experimentally as a function of the frequency (f = 0.275 to 20 kHz) and the magnetic field (h = 2 to 10 Oe, the external magnetic field being Hac = h · cos ωt, Hdc = 0) in planar high-Tc YBa2Cu3Ox-ceramic samples, whose thickness was varied over a wide range (D = 2 to 0.3 mm). A solution was found to the critical state equation in Anderson’s flux creep model; this solution describes consistently all the experimental results collected. Within the model used, the pinning potential has been shown to be temperature-dependent and decreasing with increasing temperature. It has been established that under flux creep conditions the unambiguous determination of both the critical current density and the pinning potential is possible if at least three parameters, viz., h, f, and D, are varied in the experiment.
Magnetic field “refraction” ion uniaxial type-II superconductors
Authors: Sergeeva G. G.
Published: January 2025

Peculiarities of the penetration of a magnetic field tilted at angle γ ≠ 0 to the ĉ axis are considered for uniaxial type-II superconductors with large Ginzburg–Landau parameters. It is shown that in fields 0 < H < Hc(γ) there exists quite a large temperature interval ΔT(H) where the direction of vortex lines differs from the orientation of H and varies with temperature. It is pointed out that within the ΔT(H) interval the rotation of the magnetic flux brings about a temperature dependence of the elastic moduli of the vortex lattice.
Dynamic mixed state in amorphous Nb3Ge films
Authors: Prokhorov V. G. , Kaminskii G. G. , Petrukhno Ya. A. , Tret’yachenko K. G.
Published: January 2025

Current–voltage curves and first derivatives of I–V curves were recorded in a wide range of temperatures and magnetic fields on amorphous Nb3Ge films with collectivized pinning of vortex lines. Temperature and field dependence of the magnetic flux viscous flow resistance is analyzed within the Larkin–Ovchinnikov model. A good agreement between theory and experiment is demonstrated. A H–T phase diagram is suggested for possible states of the vortex lattice.
Injection thermoelectric effect in ballistic metal–insulator point-contacts
Authors: Kulik I. O. , Shkorbatov A. G.
Published: January 2025

The electron drag emerging in a metal-insulator point-contact due to the injection of ballistic phonons from the insulator is studied. The thermo-emf in a circuit formed by the point-contact “metal-conducting film-insulator” is calculated. The possibility of spectroscopy of the transmission coefficient of phonons passing through the insulator-metal boundary is analyzed.
Magnetoresistance of point-contacts between layered conductors
Authors: Kolesnichenko Yu. A. , Tuluzov I. G. , Khotkevich A. V.
Published: January 2025

The nonlinear electrical conductivity of point contacts between conductors with a quasi-two-dimensional electron energy spectrum in a strong magnetic field H is investigated theoretically. It is found that the resistance and the point-contact (PC) spectra of electron–phonon interaction are extremely sensitive to the orientation of the vector H relative to the layers with a high electrical conductivity, and to the shape of the contact. It is shown that investigation of the dependence of PC spectra on the magnitude and direction of the field H provides information about the relaxation of electrons at various types of phonon excitations.
Inelastic relaxation time of electrons in thin bismuth films
Authors: Komnik Yu. F. , Kashirin V. Yu.
Published: January 2025

The temperature dependences of the time τφ of inelastic electron interaction have been obtained for various values of the electric current from an analysis of the magnetic field dependences of the localized correction to the conductivity of bismuth films of thickness ∼ 100 Å. The temperature dependence of the electron–phonon energy relaxation time has been obtained from the electron superheating effect which is manifested in a change in the shape of the τφ(T) dependence under the influence of the heating current. The electron–phonon scattering time is compared with the contribution of electron-phonon interaction processes to the electron phase relaxation.
Nonlinear electromagnetic excitation of anomalous sound waves in metals
Authors: Galbova O. , Ivanovsky G.
Published: January 2025

An expression for the elastic field U(x) of a double-frequency longitudinal acoustic wave is obtained at a large distance from the surface of a metal half-space irradiated by an electromagnetic wave of frequency ω. The analysis is carried out under weak nonlinearity conditions.
Spin relaxation of hydrogen atoms in solid molecular hydrogen caused by two-level systems
Authors: Buishvili L. L. , Zakharov L. Zh. , Tugushi A. I.
Published: January 2025

The effect of spin relaxation of hydrogen atoms caused by two-level systems in solid hydrogen is investigated. It is shown that two-level systems lead to a new channel of nuclear and electron relaxation and provide an explanation for the experimentally observed temperature dependence of the spin relaxation rate.
Renormalization of phonon spectra in systems with anyon excitations
Authors: Tokar’ O. I. , Fil’ D. V.
Published: January 2025

The interaction of an anyon medium with acoustic vibrations of the crystal lattice is described. In spite of the apparent analogy with two-dimensional electrons in a quantizing magnetic field, the anyon medium effectively interacts with the elastic subsystem. The longitudinal sound velocity in the superfluid state is renormalized and vanishes upon a transition to the normal phase. The magnitude of the sound velocity jump in an anyon superconductor is much larger than the corresponding value in BCS superconductors.
Electron–nuclear interactions and spin reorientation in HoFeO3
Authors: Karnachev A. S. , Moskvin A. S. , Solov’ev E. E.
Published: January 2025

Electron–nuclear interactions and spin-reorientation in HoFeO3 have been studied by the method of nuclear magnetic resonance (NMR) of 57Fe nuclei. It is found that the magnetic equivalence of Fe3+ ions is violated in the temperature range 53–62 K due to spin-reorientation phase transitions Γ4 → Γ2. The obtained experimental results are compared with the data from other works.
Effect of crystal lattice defects on T
c of transition metals (a review)
Authors: Sokolenko B. I. , Starodubov Ya. D.
Published: January 2025

We present an overview of some theoretical models that describe variations of the superconducting transition temperature Tc and of the electron-phonon coupling constant in metals with crystal lattice defects of various types. We analyze results of experimental studies of the influence of the defect structures, brought about by deformation at T ≃ 300 K and T ≪ Θ (Θ being the Debye temperature), on the Tc of transition metals with bcc (Nb, V, Ta) and hep (Re, Zr) lattices. Results of theoretical calculations are compared with experimental data on Tc in Nb with high dislocation densities. We report results of numerical computations of a few microscopic characteristics that control the superconducting parameters of transition metals with deformation-induced defects.
Vacancies in solid 4He
Authors: Dyumin N. E. , Zuev N. V. , Boiko V. V. , Grigor’ev V. N.
Published: January 2025

We have found the concentration, the isobaric formation volume, and the diffusion coefficient of vacancies in hcp and bcc 4He, based on an analysis of experiments on self-diffusion, excess heat capacity, and variations of the pressure with temperature. The results obtained agree with the wide-band picture of vacancies in helium crystals.
Electron–phonon relaxation mechanisms in thermo-emf and magnetothermo-emf of noncompensated polyvalent metals with a closed Fermi surface
Authors: II’evskii V. I. , Kopeliovich A. I. , Morgun V. N. , Chebotaev N. N.
Published: January 2025

The theory of thermo-emf in noncompensated polyvalent metals with a closed Fermi surface described by a weak pseudopotential is constructed under the conditions of predominance of small-angle electron–phonon scattering. The electron drag by phonons and the Umklapp processes are considered in detail. A qualitative explanation is offered for the experimentally observed significant difference in the thermo-emf in Al and In for H = 0. It is shown that the thermo-emf tensor Ŝ in a magnetic field H is determined by the competition between the two contributions ŜC and ŜU. The first of these contributions is associated with thermal diffusion and electron drag by a phonon wind in N-processes, and is calculated in terms of the electron and phonon heat capacities of the crystal. The second contribution is expressed in terms of the tensor components of resistance in a magnetic field and is associated with the electron drag by a phonon wind in U-processes.
Crystal electric field and dynamics of spin fluctuations in CeAl
Authors: Vasil’kevich A. A. , Ivanitskii P. G. , Slisenko V. I. , Krotenko V. T. , Maistrenko A. N. , Markiv V. Ya.
Published: January 2025

Crystal electric field (CEF) effects in CeAl are studied with the help of inelastic neutron scattering. The parameters of CEF Hamiltonian with an orthorhombic symmetry point group of a rare-earth ion are determined from the neutron spectra. The energy level diagram of the fundamental multiplet 2F5/2 of a Ce3+ ion in the CEF of CeAl is obtained. Temperature dependences of the Schottky specific heat and magnetic susceptibility are calculated. The theoretical magnetic susceptibility is compared with the experimental value.
Kinetic size effects in two-layer plates
Authors: Dekhtyaruk L. V. , Kolesnichenko Yu. A.
Published: January 2025

Exact and asymptotic expressions have been obtained for kinetic coefficients of a two-layer plate. It is predicted that their dependence on the ratio of layer thicknesses is nonmonotonic and sensitive to the nature of interaction of electrons with the boundary between the layers. A detailed numerical analysis of transport coefficients over a wide range of layer thicknesses is carried out for different values of parameters describing the bulk and surface relaxation of charge carriers.
Experimental and theoretical studies of solid N2–O2 solutions
Authors: Baryl’nik A. S. , Brodyanskii A. P. , Prokhvatilov A. I. , Freiman Yu. A. , Sumarokov V. V. , Yantsevich L. D.
Published: January 2025

The temperature and concentration dependences of the molar volume of O2–N2 solid solutions are studied in the monophase region by x-ray diffraction technique, using the phase equilibrium data obtained earlier. Anomalies are observed in the thermal expansion of phases based on α- and β–N2. Prigogine’s mean field approximation is used to study the free energy and thermodynamic properties of solid solutions N2–O2. Partial pressures of saturated vapor are calculated and it is shown that the oxygen concentration of vapor for weak solutions of O2 in N2 is more than an order of magnitude higher than the oxygen concentration in the solid phase. It is shown that the observed anomalies in the thermodynamic characteristics of solid solutions are associated with the peculiarities of orientational states of oxygen molecules in the nitrogen matrix.
Effect of orientational diffusion on the formation of H-bonded phenol complexes in an argon matrix
Authors: Plokhotnichenko A. M. , Ivanov A. Yu. , Radchenko E. D. , Sheina G. G. , Blagoi Yu. P.
Published: January 2025

The concentration dependence of IR spectra of phenol and diphenols in an argon matrix at T = 12 K is studied as well as the effect of sample annealing at a temperature 25–30 K on the band intensity of isolated molecules and H-bonded homoassociates. The influence of diffusion on the formation of complexes is studied and a simple quantitative model is constructed that makes it possible to determine the fraction of H-bonded complexes of different compositions in the sample for different concentrations of molecules having a high orientational mobility in the matrix. It is shown that dimers predominate among the H-bonded complexes of these molecules for matrix dilutions down to 1:100 on account of a strong dependence of the orientational mobility of complexes on their size. Integral extinctions of the valence vibration bands of free and H-bonded OH-groups of phenols in the Ar matrix are calculated.
Investigation of isothermal residual magnetization in the high-temperature superconductor YBa2Cu3O7–x
Authors: Gamtsemlidze T. A. , Gamkrelidze K. P. , Mirzoeva M. I. , Shoniya G. K.
Published: January 2025

The behavior of residual magnetic moment at T = 77 K is studied as a function of external magnetic field in the high-Tc superconducting ceramic YBa2Cu3O7−x. Analytical expressions for the residual magnetic moment are obtained in Bean’s critical state model by taking into account the field Hc1. A comparison of the experimental and theoretical results leads to conclusions concerning the form of the boundary condition for the residual induction. The lower critical field Hc1 is estimated as well as the value H* of the external field starting from which the entire sample is in the critical state.
Polariton damping in a monatomic crystal
Authors: Grigorchuk N. I.
Published: January 2025

An analytic expression is obtained for determining the frequency and temperature dependences of polariton damping in a monatomic crystal for an arbitrary form of the coupling function describing the interaction between a polariton and an acoustic phonon. Calculations are made in a one-phonon approximation for weak coupling in the case of a linear dependence of the energy of acoustic phonons on the wave vector and a polariton dispersion of the E(k)=ET+ℏ2k2/2m+δE/1−ℏ2k2c2ε∞ET2−1 where ET is the energy of transverse vibrations.
On momentum relaxation processes during electron collisions in two-dimensional conducting systems
Authors: Gurzhi R. N. , Kalinenko A. N. , Kopeliovich A. I.
Published: January 2025

It is shown that momentum relaxation processes associated with collisions between electrons in a two-dimensional degenerate electron gas are characterized by quite different times τs and τa for electron distribution functions symmetric and antisymmetric with respect to the momentum. The ratio of these times is given by τa/τs ≈ (T/εF)2 (T is the temperature and εF the Fermi energy). The temperature dependence of the electron-electron drag effect in two parallel heterojunctions based on GaAs/AlGaAs is explained.
Spatial separation of areas with bolometric and nonbolometric response components of high-T
c films by low temperature laser scanning microscopy
Authors: Dmitrenko I. M. , Zhuravel’ A. P. , Sivakov A. G. , Turutanov O. G. , Chukanova I. N.
Published: January 2025

Spatial separation of regions with bolometric and nonbolometric optical response mechanisms was accomplished by the laser scanning microscopy method in high-Tc films of various degrees of inhomogeneity. The behavior of the response at the interface of two differently oriented grains has been studied in a high-Tc film. We point out a qualitative similarity in the behavior of the response of the above structure and of a pure N–S interface studied previously in a low-Tc superconductor.
Interaction of α-particles with superconductive Nb/AIOx/Nb structures in single junction and array configurations
Authors: Cristiano R. , Esposito E. , Frunzio L. , Pagano S. , Barone A. , Peluso G. , Pepe G. , Akoh H. , Nakagawa H. , Takada S.
Published: January 2025

The behavior of high-quality full refractory Nb tunnel junctions under α-particle irradiation is discussed. Single junction and arrays consisting of 10 and 100 series connected junctions are investigated. The samples were irradiated by α-particles from 241Am. The role of phonons generated by the α-particles in the substrate is also considered. Preliminary results are obtained concerning both charge collection and risetime spectra.
Influence of defect structure on superconducting properties of niobium single crystals
Authors: Aksenov V. K. , Borisova I. F. , Sokolenko V. I. , Starodubov Ya. D.
Published: January 2025

We studied effect of the structure state, produced during low temperature straining (rolling to different reduction ratios at 20 K), on the superconducting parameter of (001) [110] single-crystal niobium. The variation of Tc with increasing reduction ratio δ is shown to reflect stages of the evolution of the defect structure, in particular, the initial appearance of plastic deformation localization centers; the crossover to a uniform dislocation distribution, and the origination of rotational plasticity. A complex, nonmonotone mode of variation of Tc, Hc2, and ρn was found removing the surface layers of strained crystals. The causes behind the observed effects are discussed.
Dislocation-induced increase of the superconducting transition temperature in niobium
Authors: Aksenov V. K. , Sokolenko V. I. , Starodubov Ya. D.
Published: January 2025

We investigated how the distribution of high-intensity (Nd) dislocations produced during a roll deformation at 20 K influences the superconducting transition temperature Tc of single-crystal niobium. It is shown that for uniformly distributed dislocations of densities (6–13) · 1010 cm−2 the experimental data agree well with the ΔTc calculated within the model of excess electron attraction due to dislocation vibrations. In the rotational plasticity regime, the abrupt increase of Tc is related to increased fields of electric stresses.
Electron-phonon relaxation mechanisms in thermo-emf and magnetothermo-emf of Al and In at low temperatures
Authors: Morgun V. N. , Chebotaev N. N. , Il’evskii V. I.
Published: January 2025

The experimental data for high-purity Al and the data for In available in literature are used to show that for a polyvalent noncompensated metal with a closed Fermi surface described by a weak pseudopotential, the thermo-emf and magnetothermo-emf at low temperatures are determined by the competition between two contributions in accordance with diffusion theory. The first contribution, which is associated with the thermal diffusion of electrons and phonon drag in N-processes, is expressed in terms of the electron and lattice heat capacities of the crystal and varies in a magnetic field like the Hall (Righi–Leduc) coefficient. The second contribution which is associated with phonon drag in U-processes, is expressed in terms of the magnetoresistance tensor components and contains the Peierls exponent at T < T0.
On tunnel spectroscopy of normal metals with charge- or spin-density waves
Authors: Gabovich A. M.
Published: January 2025

Current–voltage characteristics (IVC) are calculated for a tunnel current J passing through symmetric and nonsymmetric tunnel junctions whose plates are formed by metals with charge- and spin-density waves and an insulating gap Σ on a part of the Fermi surface. For a symmetric (s) junction, the IVC is antisymmetric relative to the bias voltage V and is independent of the sign of Σ. The dependence Js(V) has a root singularity for |eV| = 2|Σ|. For a nonsymmetric (ns) junction, the IVC depends on the sign of Σ. Different terms in Jns(V) have different symmetries relative to the sign reversal V → – V. On the whole, the results for both types of tunnel junctions differ significantly from the available data on superconductors obtained in the BCS model. A qualitative agreement is observed between the results of measurements by scanning tunneling microscopy for layered dichalcogenides and by point-contact spectroscopy in the compound URu2Si2. An explanation is offered for the linear dependence of the electric conductivity G on the bias voltage V in metal oxide junctions.
Effect of dislocation shape memory in bcc and fcc metals after small deformations at 4.2 K
Authors: Okovit V. S. , Chirkina L. A.
Published: January 2025

Experimental investigations have been carried out of the dislocation shape memory in the temperature interval 4.2–300 K for niobium, iron, nickel, and copper samples deformed at 4.2 K by torsion from 0.1 to 0.4%. After such a treatment, the dislocation shape memory is found to exist both in bcc and fcc metals, but the intensity and temperature of its emergence depend on the defect structure formed as a result of low-temperature deformation, as well as on the friction forces in the crystal lattice. It is shown that the extent of shape restoration in bcc metals is much larger than in fcc metals. The process occurs in three stages in bcc metals. In fcc metals, the emergence and extent of the dislocation shape memory depend on the packing defect energy (PDE). In metals with a low PDE (e.g., copper), the shape is retrieved in two stages, while in metals with a high PDE (e.g., nickel), a restoration of the shape is not observed. Physical mechanisms for the observed stages of dislocation shape memory are proposed. The temperature dependence of the shape restoration and mechanical properties of Nb, Fe, Cu, and Ni are compared. It is suggested that the nature of variation of the thermally activated part of the dislocation shape memory may serve as a criterion for the tendency of bcc metals to brittle fracture upon low-temperature deformation.
Surface layer conductivity studies in a bismuth crystal under dc skinning
Authors: Andrievskii V. V. , Komnik Yu. F. , Rozhok S. V.
Published: January 2025

The nature of magnetic field variation of the resistance of a surface layer near the trigonal face of a bismuth crystal is studied for various degrees of specular reflection of conduction electrons at the surface. Two microtips on the crystal surface, separated by a distance smaller than the bulk mean free path of electrons in zero magnetic field, were used as current and potential leads for measuring these characteristics. The specular reflection coefficient was determined by the method of electron focusing by a transverse magnetic field using for the emitter and the collector the same pair of point contacts that was used for measuring the surface layer resistance. It is established that the magnetic field dependence of the surface layer resistance is linear for both specular and diffusive reflection.
Low-temperature heat capacity of two-component substitutional solutions
Authors: Skripnik Yu. V. , Syrkin E. S. , Feodos’ev S. B.
Published: January 2025

The low-frequency dynamics of a lattice containing two-parametric substitutional impurities is studied over a wide concentration range. The restrictions for the method of coherent potential are considered, and analytic expressions for the concentration dependence of low-temperature heat capacity are derived. The results of the analysis are illustrated by numerical calculations of the change in the vibrational spectrum due to two-parametric substitutional impurities.
On long-wave spin excitations in the β-phase of solid oxygen
Authors: Vitebskii I. M. , Knigavko A. N. , Chabanov A. A. , Loktev V. M.
Published: January 2025

The spectrum of long-wave spin excitations is studied in the rhombohedral β-phase of solid oxygen possessing a noncollinear triangular antiferromagnetic ordering.
On the possibility of existence of closed shells based on boron and nitrogen
Authors: Kosevich M. V. , Shelkovskii V. S.
Published: January 2025

The possibility of formation of fullerene-like closed shells from molecules and elements characterized by electronic and steric parameters which are required for the formation of polyhedral structures is discussed. It is concluded, on the basis of a formal analogy between the structures formed by boron nitride and carbon, that compounds based on combinations of boron and nitrogen are most suitable in this respect.
Righi–Leduc effect in pure aluminum at low temperatures
Authors: Chebotaev N. N. , Uzbek E. A.
Published: January 2025

The Righi–Leduc effect in pure AI is studied at low temperatures (4–80 K) in magnetic fields varying from 0.1 to 6 T. The temperature dependence of the product of the Righi–Leduc coefficient and temperature displays a peak and a minimum in weak and intermediate magnetic fields. The presence of these extrema can be explained qualitatively by peculiarities of the electron-phonon relaxation in AI.
Elastic moduli of the Abrikosov vortex lattice of a uniaxial anisotropic superconductor
Authors: Sergeeva G. G.
Published: January 2025

Elastic moduli of the vortex lattice are calculated in the London approximation for a uniaxial anisotropic superconductor in a magnetic field H<Hc(γ,T) inclined to the axis Ĉ at an angle γ≠0 for the case when the direction of vortex lines does not coincide with the direction of the external magnetic field. It is shown that all the elastic moduli depend on the angle between a vortex line and the axis Ĉ (which differs from the angle γ) and vary with temperature and field.
Magnetic dipole excitations and ground state of the rare-earth ion in Sm2CuO4
Authors: Anders A. G. , Volotskii S. V. , Eremenko V. V. , Zvyagin S. A. , Novosad V. A. , Pishko V. V.
Published: January 2025

The nature of magnetic dipole absorption observed in Sm2CuO4 is discussed. The absorption spectrum consists of two modes whose frequency for H‖ c4 depends linearly on the magnetic field, ν/γ = ν0±H, for the gap value ν0=12.5 cm−1. The absence of the temperature dependence of the gap near TN = 5.95 K makes it possible to identify this spectrum with interdoublet transitions in the Sm ion within the ground energy level 6H5/2 split by the intracrystalline field and not with the antiferromagnetic resonance in the Sm subsystem.
Superconducting quantum interference in percolating Sn–Ge films. Fractal approach
Authors: Glukhov A. M. , Pokhila A. S.
Published: January 2025

An oscillatory magnetic field dependence of the de voltage Vdc is observed near the percolation threshold upon the passage of a low-frequency current through superconducting Sn–Ge thin-film composites. These oscillations are attributed to the quantum interference effect in a Josephson percolation system. The oscillatory structure of Vdc(H) is of fractal origin. A hypothesis concerning the mechanism responsible for the “1/f noise” is proposed.
Hydrodynamics of planar solitons near A → A1 transition in superfluid 3He-A
Authors: Baramidze G. A. , Kharadze G. A. , Vachnadze G. E.
Published: January 2025

Dynamical properties of spin–orbit solitons near A → A1 phase transition are considered in superfluid 3He-A. Coupled localized oscillations of magnetization and entropy within the twist composite soliton are investigated in the case of an open geometry. Decay of the static composite soliton after an abrupt change of the magnetic field strength is considered.