JETP Letters最新文献

The content dependences of the electronic and magnetic properties of Sr_{1 – x}La_xFeO_{3 – δ}, Sr_{1 – x}La_{x ‒ y}FeO_3 ‒ δ and Sr_{1 – x}La_xFe_{1 – z}Co_zO_{3 – δ} cubic solid solutions are studied in the homogeneity region specified by δ = 0.05–0.35, (x = 0.5), (y = 0.03), 0.05, and z = 0.05–0.15 in the coherent potential approximation taking into account correlations on localized Fe-({{t}_{{2g}}}) and Co-({{t}_{{2g}}}) orbitals. Experimental electronic spectra and magnetic moments are reproduced using X-ray diffraction and thermogravimetry data for synthesized Sr_0.5La_0.5FeO_{3 – δ} nanopowders. Lanthanum doping of SrFeO_{3 – δ} strontium ferrite on the strontium sublattice expands significantly the region of oxygen nonstoichiometry (delta ) determining the accumulated charge Q. The introduction of cobalt into the iron sublattice and cation vacancies into the strontium sublattice effectively increases the electron conductivity, optimizes the energy range of oxidation/reduction ({{Delta }_{{{text{th}}}}}), and increases the number of redox transitions in it. It is shown that the Sr_0.5La_0.5Fe_0.85Co_0.15O_2.65–2.95 solid solution, having a metallic/semimetallic electronic spectrum with the maximum number of redox transitions: Fe⁴⁺/Fe³⁺, Co⁴⁺/Co³⁺, Co³⁺/Co²⁺, and Co²⁺/Co¹⁺ in the interval of ({{Delta }_{{{text{th}}}}} sim 0.65) eV, is of interest for the creation of an electrode material for pseudocapacitors.

An approach has been proposed to directly generate a multidimensional biphoton state that combines the polarization and frequency quantum entanglement of visible and infrared modes in a microstructured fiber. The possibility of controlling polarization states and equalizing the amplitudes of all generated spectral modes without a significant decrease in the generation rate has been shown. The prospects for the use of multidimensional biphoton states in optical quantum processing and quantum communications have been discussed.

The spin echo signal of ¹⁶⁹Tm nuclei has been observed for the first time in the Li(Y_0.98Tm_0.02)F₄ dilute Van Fleck paramagnet. The anisotropy of the longitudinal and transverse relaxation rates and the width of the nuclear magnetic resonance line of ¹⁶⁹Tm nuclei relative to the [001] and [100] crystallographic axes has been detected. It has been shown that the main reason for the anisotropic behavior of relaxation rates is the dispersion of local magnetic fields of ¹⁶⁹Tm rare-earth nuclei due to the dipole–dipole interaction with surrounding magnetic ions. The correlation time of the hyperfine magnetic field on the ¹⁶⁹Tm nucleus has been estimated, which confirms its direct relationship to the longitudinal relaxation time of electron moments in the doublet excited state. The lifetime of the thulium ion in the excited state has been found to be approximately an order of magnitude longer than that in a LiTmF₄ single crystal.

The process of generating galvanic currents by an alternating magnetic field in antiferromagnetic metals and semimetals has been studied on the example of Mn₂Au and CuMnAs. It has been shown that in metallic antiferromagnets of tetragonal symmetry, the external magnetic field leads to the redistribution of the charge density, and, as a result, to the appearance of the electric polarization and bias currents. To calculate magnetogalvanic effects in these materials, a model based on the group theoretical analysis and the Lagrangian formalism has been proposed. The electrical response of the system to the alternating magnetic field varying in time according to the linear and harmonic laws has been calculated. It has been shown that an adiabatically changing external magnetic field generates an electric current, which disappears in saturation fields, and an alternating electric current with a nonzero average value arises with the harmonic modulation of the field.

The results of direct numerical simulation of plane-symmetric turbulence of water waves for potential flows within the framework of conformal variables taking into account low-frequency pumping and high-frequency viscous dissipation are presented. In this model, for a wide range of pumping amplitudes, the weak turbulence regime was not detected. It is shown that for typical turbulence parameters, the main effects are the processes of wave breaking, the formation of cusps on wave crests, which make the main contribution to the turbulence spectra with a dependence on frequency and wavenumber with the same exponent equal to –4. In this strongly nonlinear regime, the probability density of wave steepness at large deviations has power-law tails responsible for the intermittency of turbulence.

Currently, a generally accepted and widely used property of multiparticle amplitudes is the absence of simultaneous amplitude discontinuities on energy invariants of overlapping channels. The Steinmann relations are used to substantiate this property. The paper shows the presence of such discontinuities and the illegality of using the Steinmann relations to prove their absence. The existence of discontinuities means that the currently accepted form of multi-Regge amplitudes is erroneous and it should be taken into account when deriving the BFKL (Balitsky–Fadin–Kuraev–Lipatov) equation in the following approximations.

This work studies iron doping in the classical nematic superconductor Sr_xBi₂Se₃. Superconductivity is shown to be suppressed for an atomic fraction of Fe about 0.2%. At lower iron concentrations, the superconducting critical temperature and nematic superconductivity anisotropy remain unchanged. Magnetization measurements confirm Fe-induced paramagnetism. The crystal structure (lattice parameter c) and transport properties evolve smoothly with Fe co-doping, indicating uniform incorporation of Fe into the crystal matrix and demonstrating no direct link between superconductivity suppression and the magnetic nature of impurities. The influence of iron on superconductivity appears to be due to structural transformation.

A pulsed semiconductor disk laser emitting at a wavelength of 642.5 nm based on a GaInP/AlGaInP heterostructure with intracavity pumping into 25 quantum wells by 614.5-nm radiation from a dye laser has been studied for the first time. A pulsed power of ~80 W has been achieved at a pulse duration of ~0.5 μs. The power is limited by the destruction of the structure. The time modulation of radiation of the dye laser with a heterostructure inside the cavity with a period of ~6 ns equal to the cavity round-trip time has been detected.

The structure of interfacial boundaries in a liquid crystal cell, composed of sequential layers of a thin-film electrode, an alignment polymer coating, and a ferroelectric liquid crystal, was investigated using X-ray scattering and atomic force microscopy. Quantitative parameters describing the structure of transition layers were obtained, along with statistical data on interface roughness and dielectric constant distribution across the film. These data are expected to provide a link between the roughness and anchoring properties of liquid crystal materials at interfaces and give an assessment of the structural modifications occurring at each stage of the electro-optical cell assembly.

Here, we present the results of vibrating wire experiments in pure ³He (without ⁴He coverage) in nematic aerogel. We investigated the dependence of splitting of the superfluid transition temperature of ³He in aerogel on magnetic field. In addition to our previous work, we used a wider range of magnetic fields (up to 31 kOe) and managed to detect both the “upper” and “lower” superfluid transition temperatures. The solid paramagnetic ³He layer on the aerogel strands activates the magnetic scattering channel. According to theory, it should result in linear splitting at high (( geqslant 20) kOe) fields, while at lower fields the splitting is expected to be nonlinear. We were able to observe this nonlinearity, but we have a discrepancy with theoretical predictions regarding the range of fields where nonlinearity occurs. Possible reasons for this are discussed.