JETP Letters最新文献

The excess entropy ΔS with respect to the maternal crystal state has been determined from calorimetric data for 30 metallic glasses. It has been shown that the excess entropy in the supercooled liquid state ΔS_sql is a universal characteristic of a glass independent of its thermal treatment. Six parameters often used to estimate the glass-forming ability of supercooled melts have been calculated for the same metallic glasses. It has been shown that all six parameters increase with ΔS_sql and the glass-forming ability of supercooled melts increases with their structural disorder. A possible mechanism to implement this relation has been discussed.

A method has been proposed for photoinduced hyperthermia of pathogenic Gram-negative bacteria P. aeruginosa using Gd₂O₃:Yb micropowder. It is based on the possibility of laser excitation of anti-Stokes luminescence on ytterbium ions in the gadolinium oxide micropowder, which allows us, on the one hand, to heat the powder to the required temperature and, on the other hand, to accurately control the powder temperature using remote luminescent thermometry. It has been demonstrated that the long-term irradiation of the Gd₂O₃:Yb micropowder with 1035-nm nanosecond laser radiation changes the shape of anti-Stokes luminescence spectra associated with micropowder heating in the range from 27 to 63°C. The application of the proposed photoinduced hyperthermia method to a mixture of solutions of the Gd₂O₃:Yb micropowder and P. aeruginosa bacteria demonstrates a decrease in the bacterial population by 90%.

A number of open questions remain in the manipulation of the spins of colliding beams, which is a key aspect in the operation of polarized beam colliders such as the Nuclotron-based ion collider facility (JINR, Dubna, Russia) and the electron ion collider (BNL, United States). The spin transparency regime, which is the only realistic regime to control the deuteron polarization, has not yet been approved experimentally. With the existing configuration of the JINR accelerator complex, a pilot spin transparency experiment could be performed on a proton beam in the Nuclotron synchrotron. The dynamics of the proton beam polarization during the fast crossing of spin resonance guided by spin navigators based on regular orbit-steerer dipoles has been analyzed in this work. A scheme has been designed to compensate the coherent action of Nuclotron lattice imperfections on spin. In this scheme, the spin field induced by lattice imperfections is determined from the adiabatic deviation of spins in the resonance region, taking into account the synchrotron energy modulation. Integer-resonance strengths can be compensated down to the limits conditioned by orbital beam emittances. The numerical simulation of the proposed spin compensator has confirmed that the spin transparency regime in an imperfect Nuclotron lattice with a strongly distorted closed orbit can be experimentally verified.

The nuclear quadrupole resonance study of the electron-deficient substitution in the promising thermoelectric material FeGa₃ resulting in the poorly studied Fe_0.92Re_0.08Ga₃ and Fe_0.92Mn_0.08Ga₃ compounds has been carried out. The doping of compounds of this structure type promotes the study of the dependence of the thermoelectric characteristics on the electronic structure and finally makes it possible to increase the thermoelectric efficiency, which is very important for applications. Both compounds exhibit pronounced signatures of the formation of an additional acceptor band inside the main band gap, which is determined by rhenium and manganese substituent atoms. Nuclear quadrupole resonance spectra, as well as nuclear spin–lattice relaxation and its temperature evolution, are significantly different for the compounds under study. This difference is due to different statistical distributions of substituent atoms (predominant formation of homo- and heterogeneous dumbbells in the rhenium- and manganese-substituted compounds, respectively) caused by their outer electron shells.

The dependence of the superparamagnetic blocking temperature on an external magnetic field T_B(H) has been studied and analyzed for a nickel ferrite nanoparticle powder system in order to establish the influence of magnetic interparticle interactions on superparamagnetic blocking. The features of this system are: (i) a small particle size (~4–5 nm on average); (ii) a pronounced “core/shell” structure of particles, in which the magnetic moment of a particle is formed by a ferrimagnetically ordered core, while the spins of the surface layer, about 1 nm thick, do not contribute to this magnetic moment. The random anisotropy model, which describes the influence of magnetic interparticle interactions on the T_B value in the external field, is used to reproduce the experimental dependence T_B(H) obtained by static magnetometry. The analysis has demonstrated strong magnetic interactions in the studied system, which are manifested in a sharp decrease in the T_B value in the weak-field region, and has made it possible to quantitatively estimate the intensity and energy of magnetic interparticle interactions, as well as to determine the magnetic anisotropy constant of individual particles (without the influence of magnetic interparticle interactions). The role of the subsystem of surface spins, which, according to the imaginary part of the magnetic susceptibility, exhibits signatures of collective behavior, is discussed as a possible source of magnetic interparticle interactions.

We have observed numerically the resilience phenomenon for ocean wind-driven waves, where the wave spectra return to their original self-similar form after a strong perturbation. This self-similar behavior is seen as the manifestation of a statistical attractor associated with generalized spectra of Kolmogorov–Zakharov. We have confirmed this interpretation through numerical simulations of random water wave field within the kinetic (Hasselmann) equation. This equation with specific source functions similar to those of conventional wave forecasting models exhibits families of exact self-similar solutions. These source functions minimize the “non-self-similar” background, allowing us to evaluate the “clean rates” of wave spectra resilience. We use the indices of the exact self-similar solutions as parameters for the attractors of numerical solutions in a two-dimensional phase space.

The ferroelectric soft mode in polycrystalline pristine SrTiO₃ and weakly doped SrTiO₃:M (M = 2 at % Fe, Ni, Mn, Co) thin films on (001) MgO substrates has been studied using time-domain terahertz spectroscopy. Spectra of real and imaginary parts of film permittivity were determined in the frequency range of 5–100 cm^–1 at temperatures between 5 and 300 K. Central frequency and dielectric contribution of the ferroelectric soft mode show Barrett-like temperature dependencies similar to crystalline SrTiO₃. Large negative values of Curie temperature and enhanced positive values of Barrett quantum temperatures are discovered indicating that doped SrTiO₃ thin films are farther from ferroelectric phase transition than SrTiO₃ crystals.

The average domain size is calculated for zero and nonzero absolute values of the local field in the ( pm J) Ising spin glasses in 2D and 3D at different temperatures using Monte Carlo simulations. The absolute values of the local field determine the spin flip probability, and thus the obtained domain sizes shed light on dynamical heterogeneities in glasses, which are currently being actively studied. It turns out that the average domain size for nonzero absolute values of the local field, corresponding to slow spin dynamics at low temperature, increases and saturates with decreasing temperature, mainly due to an increase in the probability of finding nonzero local fields. However, a slight effect of spatial correlations of the local field is also revealed. These results can be useful for understanding the nature and specific features of glass transition and dynamical heterogeneities in glasses.

Various properties of crystal clusters (i.e., clusters consisting of particles with six nearest neighbors) in a two-dimensional Yukawa fluid have been considered for the first time in a wide temperature range beginning with the melting temperature. With increasing temperature, the concentration of crystal particles (which noticeably prevail in a melt) decreases slowly, while the defect concentration increases, which results in the formation of large clusters consisting of defects and in the degradation of large crystal clusters in the considered two-dimensional fluid. Their characteristic size and shape change sharply in a narrow temperature range. The comparative analysis of crystal clusters and clusters consisting of topological defects has been performed. Their size distributions and other structural characteristics have been obtained.

In a layer of a chiral liquid crystal with negative dielectric anisotropy and the thickness d corresponding to the second Grandjean zone ((3{{p}_{0}}{text{/}}4 < d < 5{{p}_{0}}{text{/}}4), where ({{p}_{0}}) is the natural helical pitch) under the action of a planar electric field, an orientational transition occurs from the ground state twisted by the angle (2pi ) to a topologically equivalent untwisted state (0 state). Although the 0 state is metastable and long-lived, it can rapidly be transformed back to the (2pi ) state by an electric field pulse of a comparatively small amplitude. The direct transition to the 0 state is induced by the interaction of the electric field with negative dielectric anisotropy, while the rapid reverse transition can be attributed to the flexoelectric interaction.