Different types of high performance cryogenic helium units with dynamic-action machines are proposed. The creation of a helium refrigerator with an energy-generating cryogenic stage (ECS), in which helium is compressed at a temperature of 85.8 K in a cold centrifugal compressor, is also considered. The optimization of the refrigerator with an ECS is performed at the same cooling capacity of 576 W,

The molecular dynamics method is used to study the structure of two-dimensional clusters that can be created in electronic systems above the surface of superfluid helium, using triangular, square, hexagonal and round holding electrode geometries. Clusters with a fixed surface density of 108 cm−2, but different numbers of particles (from 3 to 406) are considered. The spatial configurations of particles

The dynamics of thermal radiation accompanying the condensation of tungsten nanoparticles in superfluid helium and vacuum was studied experimentally in the visible range. It was shown that during the first 100 μs the accompanying thermal energy of process in the case of superfluid helium is considerably higher than in vacuum at comparable temperatures after that it levels up. From a standpoint of the

The effect that the partial substitution of Cd for Y has on the mechanism of excess conductivity formation in polycrystalline Y1−хCdxBa2Cu3O7−δ with x = 0 (Y1), 0.1 (Y2), 0.3 (Y3), and 0.4 (Y4) is investigated. The resistivity ρ of the samples increases markedly with increasing x, and the critical temperature of the superconducting (SC) state transition, Tc, decreases. The mechanism responsible for

In the present paper, we have proposed the experimentally achievable method for the characterization of the collective states of qubits in a linear chain. We study a temporal dynamics of absorption of a single-photon pulse by three interacting qubits embedded in a one-dimensional open waveguide. Numerical simulations were performed for a Gaussian-shaped pulse with different frequency detunings and

Here we present calculations of the critical current of dc SQUID based on Josephson junction with un-conventional current-phase relation. We analyzed two cases of current-phase relation of junction: with anhar-monic and Majorana term. It is shown that the changing of the critical current in the case of the small geo-metrical inductance of dc SQUID based on Josephson junctions with unconventional current-phase

The main elastic moduli and piezoelectric modulus have been measured in holmium alumoborate single crystals. The renormalization of the permittivity, piezoresponse, and sound velocities, driven by the nematic-like paramagnetic phase in the sample, is considered. A significant variability of the results is detected, which is caused, presumably, by the fact that, under the action of external fields,

The φ0 junction demonstrates a rich variety of dynamical states determined by parameters of the Josephson junction and the intermediate ferromagnetic layer. Here we find several peculiarities in the maximal amplitude of magnetic moment m ^ y, taken at each value of the bias current, which we correlate to the features of the IV-characteristics of the φ0 junction. We show that a kink behavior in the

The electrical resistivity and thermal conductivity as functions of temperature, for an equiatomic Fe–Ni system are studied. The samples were obtained from nickel and iron powders by a 10 min electroconsolidation at a temperature of 1100 °C, pressure 35 MPa, and current ∼5 kA, and studied in the range of 4.2–300 K. It was found that the electrical and thermal conductivity of the electroconsolidated

The author has performed a theoretical analysis of the electronic structure of an elbow junction in single-walled “armchair” (4,4) and “zigzag” (7,0) carbon nanotubes consisting of 131 carbon atoms, as well as in pure carbon “armchair” (4,4) nanotubes consisting of 128 atoms, and “zigzag” nanotubes consisting of 126 atoms. It is shown that in the case of the elbow junction under study, a metal-semiconductor

Using X-ray diffraction analysis methods, the authors have studied the effect of stepwise isothermal annealing in the temperature range 150–670 C on the deformation microstructure parameters of cryodeformed VT1-0 titanium with micron, submicron, and nanoscale grain sizes. The structural states were obtained by rolling at liquid nitrogen temperature. This study discusses the influence of dislocations

The mechanical properties of a high-entropy CrMnFeCoNi2Cu alloy with an FCC lattice have been studied in a broad temperature range (4.2–350 K). The microhardness and Young’s modulus were measured at 300 K for two structural states. The temperature dependences of the yield strength, deforming stress, and strain rate sensitivity have been obtained. It was found that a high-strength state is realized

The topology of phase portraits for nonlinear oscillators driven by a periodic force undergoes significant changes within a narrow interval of the driving force frequencies v. This property leads to nonintegrability of the equations of motion, and stochastization of their solutions when v is periodically modulated. Such behavior is due to the violation of adiabaticity and destruction of the integral

A classification of the equilibrium states of single-sublattice magnets with spin s = 3/2 and SU(4) symmetry of the exchange interaction is developed. The study is based on the concept of quasi-averages and the principle of residual symmetry of degenerate equilibrium states. The transformation properties of the magnetic degrees of freedom are used to derive a system of equations for the order parameters

The theory of the giant conventional and inverse magnetocaloric effects (MCEs) is advanced on the basis of the theory of magnetism developed by A. I. Akhiezer, V. G. Bar’yakhtar, and S. V. Peletminsky in the classic monograph “Spin Waves”. The MCE in the shape memory alloy undergoing the first-order phase transition from the cubic ferromagnetic (FM) phase to the tetragonal antiferromagnetic (AFM) phase

Diffusion Magnetic Resonance Imaging (MRI) plays a very important role in studying biological tissue cellular structure and functioning both in health and disease. Proper interpretation of experimental data requires the development of theoretical models that connect the diffusion MRI signal to salient features of tissue microstructure at the cellular level. In this short review, we present some theoretical

It is well-known that a spin-transfer torque caused by a dc electric current can excite in a two-dimensional ferromagnetic film exchange-dominated magnetic solitons, often called “spin-wave bullets”, under the condition of a negative nonlinear shift of spin wave frequency. In this work, we demonstrate that in a quasi-one-dimensional (1D) case, e.g., in a nanowire spin-Hall oscillator, it is possible

A heterostructure composed of two parallel homogeneous layers is studied in the limit as their width and the distance between them shrinks to zero simultaneously. The problem is considered in one dimension and the squeezing potential in the Schrödinger equation is chosen in the form of a piecewise constant function. As a result, two families of point interactions with bound state energy are realized

We study numerically the integrable turbulence in the framework of the focusing one-dimensional nonlinear Schrodinger equation using a new method — the “growing of turbulence”. We add to the equation a weak controlled pumping term and start adiabatic evolution of turbulence from statistically homogeneous Gaussian noise. After reaching a certain level of average intensity, we switch off the pumping

A low-temperature feature is detected in nanogranular magnetic films with perpendicular anisotropy that have a low-field positive magnetoresistance: positive magnetoresistance is observed during the initial magnetization of the demagnetized sample, but is absent when the magnetic field is removed and/or during subsequent magnetizations. This effect is studied using a Cox(Al2On)1−x film with x = 0.60

We propose a new method of constructing the effective theory for a multicomponent low-dimensional dilute Bose gas. The method is based on obtaining and solving renormalization group equations for all many-body interactions of density-density type in the one-loop approximation. In contrast to the standard approach based on two-body interactions, our method does not rely on the introduction of density-dependent

There are the static and dynamical spin chiralities. The former is a result non-collinear spin structure. The second takes place in the magnetized samples. Both are considered and illustrated by results of the neutron scattering experiments.

Based on the coincidence of the dimensions of the Newtonian gravitational constant GN and the Fermi phenomenological constant GF for weak forces in the natural system of units (ħ = c = 1), a version of the quantum field theory of gravity is proposed, whose structure is similar to that of the Glashow–Salam–Weinberg theory of the unified electroweak interaction.

The controlled decomposition of solid solutions in the vicinity of interphase boundaries separating domains of the coexisting antiferroelectric and ferroelectric phases opens new fields of applications for these materials. The lead zirconate–titanate based solid solutions are considered as an example of substances suitable for creation of materials with the negative refractive index. Manufactured composites

Ferromagnetic resonance in multilayer metal nanostructures containing an antiferromagnetic layer of variable thickness is studied. The contribution to the linewidth of the ferromagnetic resonance that is caused by spin-pumping current dissipation in an exchange-coupled antiferromagnetic/ferromagnetic bilayer is determined. The dissipative processes that occur in the bulk of the antiferromagnet and

A spin wave (SW) propagating in an external electric field acquires an extra phase, the so-called Aharonov– Casher phase. To linear order, that is equivalent the SW frequency shift linear in both the applied electric field and the wave vector of SW’s and can be described by adding effective Dzyaloshinskii–Moriya-like interaction between spins. This effect is a promising way to control and manipulate

For a plane and quasi-plane SH-type bulk wave incident from the outside onto a system of equidistant antiferromagnetic dielectric layers, the inclusion of the spatial dispersion in the antiferromagnet as a hyperbolic magnetoacoustic medium induces a number of resonant refractive anomalies: the effects of total reflection (transmission) and the formation of discrete localized magnon-phonon states against

We have used the method of Wannier functions to calculate the frequencies and profiles of spin waves localized in one-dimensional magnonic crystals due to a gradient in the bias magnetic field. This localization of spin waves is analogous to the phenomenon of Bloch oscillations of quantum-mechanical electrons in crystals in a uniform electric field. As a convenient yet realistic model, we consider

A mechanism is proposed for transferring magnon energy from one ferromagnet to another by tunneling magnons through a bridging ferromagnetic wire that connects ferromagnets. In the framework of the model of Bose gas for the magnons, expressions are found for the power of the transferred magnon energy from a ferromagnet having a higher temperature to a colder ferromagnet. It is shown how the efficiency

The motion of domain walls in ferrimagnets near the sublattice spin compensation point is studied theoretically, when there is an exchange enhancement in the limiting velocity of the wall. Nonlinear regimes of high-velocity nonstationary wall motion are found. A magnet parameter region in which the collective variable approach is invalid, is detected. In this region, the wall motion is accompanied

Topological charges are calculated for a number of exact three-dimensional analytical solutions to the Landau–Lifshitz equation, which describe the distributions of the vector fields for the vectors of antiferromagnetism and antiferromagnet magnetization. It is shown that in the case of samples with dimensions that are comparable to the characteristic scales of topological objects of the antiferromagnetism

In the framework of the Landau–Lifshitz equations for discrete systems, the dynamics of two classical magnetic moments modeling weakly coupled magnetic nanodots, layers of quasi-two-dimensional magnets and two-sublattice magnets are considered. Exact solutions of dynamic equations are found and investigated. Particular attention is paid to the study of essentially nonlinear inhomogeneous states with

We summarize our experimental findings in the arrays of Ni80Fe20 circular nanodots with diameter 300 nm and thickness 20 nm ≤ L ≤ 100 nm, probed by broadband ferromagnetic resonance spectroscopy in the absence of external magnetic field. Spin excitation modes related to the vortex core gyrotropic dynamics were observed in the gigahertz frequency range. Micromagnetic simulations revealed that they are

A novel family of disordered systems is proposed. This family belongs to the class of systems containing random substitutional non-Hermitian impurities. We limit our consideration to a rather simple case when the presence of substitutional point defects results in the model Hamiltonian featuring a diagonal disorder. In contrast to known models of non-Hermitian impurities, the nonzero density of states

The relative stability of diamond and graphite is readdressed from the new perspective of deductive molecular mechanics. Unlike most theoretical studies that are conducted numerically, this article uses an analytical model to gain insight into the fundamental reasons behind the quasi-degeneracy of these allotropes with very different bonding patterns. The relative energies of the allotropes are derived

Current-voltage characteristics of a single-electron transistor with a vibrating quantum dot were calculated assuming vibrons to be in a coherent (non-equilibrium) state. For a large amplitude of quantum dot oscillations we predict strong suppression of conductance and the lifting of polaronic blockade by bias voltage in the form of steps in I-V curves. The height of the steps differs from the prediction

The linear response of the molecular aggregate chain with the random distribution of the strength of the neighboring intermolecular interactions to the bichromatic electromagnetic field has been calculated. The presence of the linearly polarized field produces additional resonance absorption at the combined frequencies of the circularly polarized and linear polarized field. The strength of the absorption

The magnetic properties of narrow zigzag graphene nanoribbons with periodically embedded atoms of transition metals have been studied in the framework of Heisenberg spin Hamiltonian. We have proposed the simple effective model to give a semi-qualitative description of the peculiarities of magnetization profiles of the systems under consideration. This model can be used for an arbitrary value of spin

The Wolff cluster Monte Carlo algorithm is used to investigate the effect of frozen nonmagnetic canonically distributed impurities on the phase transitions in a two-dimensional Potts model with the spin state q = 5. Systems with linear dimensions L = 20–160 at spin concentrations p = 1.0 and 0.9 are considered. Using the fourth-order Binder cumulant method and the histogram analysis method it is shown

The phase transitions and critical properties of the three-dimensional stacked triangular-lattice Ising antiferromagnet in a magnetic field are studied using the replica Monte Carlo method. The nature of the phase transitions is analyzed on the basis of the histogram method. It is established that a second-order transition occurs in the field range of 0 ≤ h ≤ 6. At a high field, the degeneracy of the

Structural, magnetic, and thermal studies of DyCr3(BO3)4 have been carried out. Structural studies showed that the sample contains two phases, with the contents of the rhombohedral (R32) and monoclinic (C2/c) phases being the same, within the accuracy of the method. The lattice parameters for each phase were determined (the rhombohedral: a = 9.461 Å, c = 7.488 Å; the monoclinic: a = 7.394 Å, b = 9

The dependence for the frequencies of the internal modes on the external field in spiral structures in easy-plane antiferromagnets with a small in-plane anisotropy are studied theoretically in a wide region of the fields including the spin-flop transition field. The theoretical results are compared with the known experimental data for the antiferromagnetic resonance in NdFe3(BO3)4. This comparison

This article investigates the dynamic properties of two-dimensional nonlinear magnetic metamaterials consisting of nanoscale elements. The authors propose a model for a two-dimensional lattice of capacitively and inductively coupled split rectangular nanoresonators. It has been shown that the long-wave dynamics of this two-dimensional lattice are described by a regularized two-dimensional nonlinear

Spin valves based on materials in which the spin-flip is suppressed by the spatial separation of charge carriers, while maintaining electric neutrality in the valve volume, are considered. The possibility of using these valves as electric batteries is discussed. Regulating the potential difference on the valve, one can expect the effects of incommensurability of the type of “devil's staircase” associated

Magnetic circular dichroism (MCD) and absorption spectra of multiferroic HoFe3(BO3)4 of 5I8 → 5F2 and 5F3 f–f transitions are measured at T = 90 K. The absorption spectra are expanded into Lorentzian components, and the transition intensities are obtained. The Zeeman splitting of some transitions is determined using the MCD and absorption spectra. The MCD spectra and Zeeman splitting are theoretically

The smooth (001) surfaces of SrTiO3 (STO) single crystals were investigated by the reflection high-energy electron diffraction method in the temperature range from 5.5 to 300 K. The Raman scattering confirmed the high quality of STO samples. Five structural anomalies were found depending on temperature. The antiferrodistortive phase transition from the cubic structure to tetragonal, observed in the

The review is devoted to the conductive properties of the multielement compounds such as lanthanum and erbium cobaltites. These properties are associated with a dopant-controlled interaction of the delocalized electrons with the local magnetic moments. It is considered the basic physical mechanisms that determine the transport properties of perovskitelike materials. It is given main experimental results

Magnetoconductivity oscillations and absolute negative conductivity induced by nonequilibrium populations of excited subbands in a degenerate multisubband two-dimensional electron system are studied theoretically. The displacement from equilibrium, which can be caused by resonant microwave excitation or by any other reason, is assumed to be such that electron distributions can no longer be described

The propagation of intense rectangular thermal pulses in superfluid helium is studied numerically using superfluid turbulence hydrodynamics with various equations for vortex line density dynamics. It is shown that the experimental data are most adequately described by the Vinen equation. The impact of the background vortex line density on the dynamics of the pulses at different temperatures of the

In this work, we analyze the temperature dependencies of resistance and magnetoresistance for two RuSr2(Eu1.5Ce0.5)Cu2O10−δ ceramic samples, one of which was left in the as-prepared state while another one was oxygen saturated. The measurements on these samples were made soon after preparation and repeated after their long storage (10 years) in an ambient atmosphere when they lost most of their over-stoichiometric

The authors have detected an anomalous X-ray optical effect in the Ni(1−x)Wx/TiN system, which consists of a rise in the intensity of certain diffraction lines of the substrate with increasing coating thickness. Based on the observed effect, this article has conceptualized the optimization of the architecture of two-layer systems with a substrate of TiN-coated NiW paramagnetic alloys, which provides

This study analyzes a non-threshold electromagnetic radiation detector, which is a current-carrying superconducting film with a normal domain. The normal domain is formed as a result of heating a portion of the film by an external heat source, and Joule heat in the domain. The detection mechanism consists in the fact that the heating of the film by electromagnetic radiation leads to an increase in

The Ginzburg–Landau method is used to conduct a phenomenological analysis of how the sample thickness impacts the incommensurate spin states in the TbMnO3 centrosymmetric ferroelectromagnet. The analysis is performed using the first-harmonic approximation, and provides a qualitative confirmation of the experimentally observed decrease in the film modulation vector at a decreasing temperature, as well

The crystal structure, magnetic susceptibility as a function of temperature χ(T) in the range 5–400 K, and the hydrostatic pressure effect on χ at fixed temperatures T = 78, 150, and 300 K, were studied in perovskite-like compounds La1−xPrxCoO3 (x = 0, 0.1, 0.2, and 0.3). The obtained experimental data were analyzed using a two-level model with an energy gap Δ between the ground and excited states

The ferromagnetic resonance (FMR) in the shape memory alloys (SMAs) exhibiting structural cubic-tetragonal phase transition has been studied. The influence of instability and spatial inhomogeneity of crystal lattice on the FMR spectra of twinned ferromagnetic SMAs films has been analyzed using statistical model of ferromagnetic martensite. It has been shown that the abnormally strong temperature dependence

The temperature evolution of the LiNiPO4 single crystal Raman spectra in a region of 2–25 K, which includes a phase transition to a magnetically ordered state, is studied. For the first time, magnetic contribution in the Raman spectra was divided into single-magnon and two-magnon excitations at 2 K. The energies of the detected single-magnon excitations are in good agreement with the data obtained

A combined superconducting magnetic system with a uniform field of up to 20 T has been developed. The system contains several solenoidal sections and a magnetic flux concentrator consisting of hydroextruded dysprosium. The sections are wound from NbTi, Nb3Sn wires and Nb3Sn ribbon. A magnetic shield made out of Nb3Sn ribbon is applied in order to increase the uniformity of the magnetic field. The magnetic

The dependences of the current and integral intraband terahertz electroluminescence intensity on the electric field in the n-InGaAs/GaAs heterostructures with asymmetric double tunnel-coupled quantum wells under the conditions of bipolar lateral transport are established to differ qualitatively for different interwell barrier widths. In the case of the thick (∼50 Å) barriers at electric fields less

The temperature dependences of the longitudinal and transverse conductivity of YВа2Сu3О7−δ single crystals irradiated with high-energy electrons were measured. It was found that, in contrast to unexposed YВа2Сu3О7−δ single crystals, the absolute value of the electrical resistivity anisotropy ρc/ρab significantly decreases with an increase in the number of structural defects in the experimental sample

This article investigates the magnetic susceptibility, χ(T), of the two-phase (R32 + C2/c) crystal LaCr3(BO3)4 in the temperature range 2–300 K for two orientations of an external magnetic field. It has been established that both structural modifications of lanthanum chromium borate are ordered antiferromagnetically, with each of them having its own Néel temperature (6.5 and 8.5 K). It has been shown