Tunneling spectroscopy of slightly overdoped pnictides BaFe$_{1.88}$Ni$_{0.12}$As$_2$ in the superconducting and normal state
Tunneling spectroscopy of slightly overdoped pnictides BaFe$_{1.88}$Ni$_{0.12}$As$_2$ in the superconducting and normal state
I. A. Nikitchenkov$^1$, A. D. Ilina$^2$, V. M. Mikhailov$^2$, K. S. Pervakov$^2$, V. A. Vlasenko$^2$, S. A. Kuzmichev$^{1,2}$, T. E. Kuzmicheva$^2$
Using tunneling spectroscopy, we measured current-voltage characteristics (CVC) and dynamic conductance spectra dI(V)/dV of SnS tunneling contacts in single crystals of slightly overdoped superconducting ferro-pnictide of nominal composition BaFe$_{1.88}$Ni$_{0.12}$As$_{2}$ with bulk critical temperature $T_c = 18$ K. Besides the Andreev structure, a strong nonlinearity is observed in the obtained curves both in the superconducting and normal state. For the temperature range $4.3-26.4$ K we determined the positions and temperature dependences of the observed dI(V)/dV-features irrelated to the superconducting state. Additionally, we discuss the possible origins for the appearance of the observed features.
Show AbstractMagnetic properties of iron oxide nanoparticles in the matrix of potassium-aluminoborate glasses subject to thermoradiation treatment
Magnetic properties of iron oxide nanoparticles in the matrix of potassium-aluminoborate glasses subject to thermoradiation treatment
M. K. Salakhitdinova$^1$, E. M. Ibragimova$^2$, O. K. Kuvandikov$^1$
The paper presents the results of investigations of the magnetic properties of glasses of the composition K2O•Al2O3•B2O3 (KAB) with the addition of Fe2O3 2.0 and 3.0 wt.%, subjected to radiation treatment in 60Co gamma field at dose rate of 236 R/s for 2 hours at room temperature and when samples are heated to 423 K. Both under radiation and thermoradiation exposure, the magnetic susceptibility of glasses follows the Curie–Weiss law at 4.2–200 K and slightly deviates from this dependence at 200–340 K. The weakly pronounced magnetic hysteresis with low coercive force was detected at low temperatures against the background of magnetization that depends almost linearly on the field. An analysis of data on the temperature and field dependences of magnetization in weak and strong fields, combined with data on structural and optical properties, indicates that mainly Fe2O3 nanoparticles in the uncompensated antiferromagnetic state are formed in glasses, as well as an insignificant amount of dissociated Fe and Fe3O4 ions.
Show AbstractPattern analysis of fractal-like systems
Pattern analysis of fractal-like systems
Yu. V. Ryzhikova, S. B. Ryzhikov$^2$
The features of the Fourier spectra of fractal-like systems are studied. On the basis of theoretical studies, the features of the scaling invariants of the objects under consideration in light fields are determined, which manifest themselves in the form of stable local formations - patterns. Particular attention is paid to the problem of stability of the ratios of the scaling characteristics of the analyzed systems and their Fourier transforms. The possibility of identifying and systematizing various fractal systems based on the estimation of their scaling parameters is considered. An analysis of the stability of the scaling parameters of the probing radiation to changes in the parameters of the systems under study indicates that the pattern approach to improving the methods of optical diagnostics is promising.
Show AbstractApproximate equations for the reflection from a quarter-wavelength absorbing layer
Approximate equations for the reflection from a quarter-wavelength absorbing layer
A. O. Shiryaev, K. N. Rozanov, D. A. Petrov
The paper proposes a theoretical and numerical study of the quality criteria of radar absorbing layer. Simple analytical expressions for the minimum of the reflection coefficient of a homogeneous absorbing layer are obtained. It is shown that this quantity is not a correct characteristic of absorption. To describe the quality of an absorber, other quality criteria are needed, such as relative bandwidth of operating waveband or the ratio of the operating waveband to the layer thickness. The first of these values may be useful in obtaining a broadband absorber, and the second, in obtaining a small thickness of an absorber.
Show AbstractQuantum hydrodynamic representation of the exchange interaction in the theory of description of magnetically ordered media
Quantum hydrodynamic representation of the exchange interaction in the theory of description of magnetically ordered media
P. A. Andreev$^1$, M. I. Trukhanova$^{1,2}$
Ferromagnets, multiferroics and other magnetically ordered materials are described by various models of the evolution of the magnetization of the medium. In this paper, we develop the method of many-particle quantum hydrodynamics for such media. We use the Heisenberg Hamiltonian and derive an equation for the evolution of macroscopic magnetization, corresponding to the non-dissipative version of the Landau-Lifshitz equation for particles with spin 1/2. It is shown that the well-known form of the contribution of the exchange interaction to the Landau-Lifshitz equation arises in the third order in terms of the interaction radius. The possibilities of the systematic generalization of the result obtained are discussed when considering the fifth order in the interaction radius or when considering particles with a large spin.
Show AbstractSpectral barcode based on one-dimensional photonic crystal with continuous refractive index modulation
Spectral barcode based on one-dimensional photonic crystal with continuous refractive index modulation
S. E. Svyakhovskiy, N. I. Pyshkov
This paper demonstrates an example of optical information encoding using the spectral response of a photonic crystal. The spectral dependence of the reflection coefficient of a one-dimensional photonic crystal reproduces the sequence of the EAN-13 standard barcode. An algorithm for building the structure of a photonic crystal based on a given encoded sequence of 12 digits was developed. This structure was experimentally implemented, its spectral response allows to decode the original encoded sequence.
Show AbstractSuppression of local electron-phonon interaction in pi-conjugated oligomers and its monitoring using Raman scattering
Suppression of local electron-phonon interaction in pi-conjugated oligomers and its monitoring using Raman scattering
A. Yu. Sosorev
For efficient operation of many organic electronic devices, organic semiconductors with high charge carrier mobility are required. However, in most of the known organic semiconductors, the charge mobility is low, since it is limited by the strong local electron-phonon interaction. In the present work, using the example of thiophene-phenylene co-oligomers, a class of organic semiconductors that combine a sufficiently high charge mobility with light emission and therefore promising for light-emitting transistors and electrically pumped lasers, the mechanism of suppression of the electron-phonon interaction by introducing electronegative atoms or an additional thiophene ring is studied. It was found that such structural changes alter the contribution of various vibrational modes to the local electron-phonon interaction, in particular, to the suppression of the contribution of the low-frequency torsion mode. In addition, it is shown that for the two modes that make the largest contribution to the local electron-phonon interaction in an unsubstituted oligomer, this change correlates with their intensity of Raman scattering, and this confirms the promise of studying the electron-phonon interaction using Raman spectroscopy. The results obtained improve the understanding of the relationship between the local electron-phonon interaction and the molecular structure of organic semiconductors, which is extremely important for the directed design of such materials with high charge mobility.
Show AbstractHow the Hubble flow in an anisotropic Universe looks like?
How the Hubble flow in an anisotropic Universe looks like?
A. V. Toporensky$^1$, I. V. Stepanyan$^2$, R. V. Ivanov$^3$
Using formulae for light propagation, redshift and photometric distance in a Bianchi I anisotropic Universe, we create a picture of the Hubble flow that could be observed by a hypothetical observer in the anisotropic Universe. The algorithm used can be applied (after some modification) for more complicated visualizations of a sky seen by an observer in strong gravitational fields.
Show AbstractTest experiment to determine the time distribution of the background between mmf accelerator pulses on the RADEX channel
Test experiment to determine the time distribution of the background between mmf accelerator pulses on the RADEX channel
M. V. Mordovskoy$^1$, A. A. Kasparov$^1$, V. M. Skorkin$^1$, I. V. Surkova$^1$
The authors offer works using the MMF INR RAS neutron channel to study the cluster structures in light nuclei, in particular, α-4n-α and 8Be-4n in the highly excited state 12Be*. This needs the registration of charged particles from the 12Be* β-decay during its formation in the n + 13C reaction in the intervals between cascade neutron pulses. The paper presents the first results of an experiment on measuring the spectra and time distributions of gamma-quanta and neutrons using a proton beam of 50 Hz and a duration of 0.3 μs.
Show AbstractA test experiment on determining the cluster structure of highly excited states of $^6$Li
A test experiment on determining the cluster structure of highly excited states of $^6$Li
M. V. Mordovskoy, A. A. Kasparov, A. A. Afonin, V. P. Zavarzina, A. S. Kurlovich, V. V. Mitcuk, I. V. Surkova
The paper presents the results of test measurements to determine the possibilities of studying the cluster structure of highly excited states of the 6Li nucleus in the 6Li(n,3He n)3H reaction on the RADEX neutron channel of the Institute for Nuclear Research of the Russian Academy of Sciences. In the experiment, scattered neutrons were detected in coincidence with the decay products of highly excited states (helium-3). The first experimental data on the excitation energy of the 6Li nucleus have been obtained.
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