ALBERT

Description: The topology and conditions of nucleation of magnetic inhomogeneities at defects of a uniaxial ferromagnet have been investigated theoretically. It has been shown that, for specific material parameters, two types of inhomogeneities corresponding to a 0-degree domain wall, which differ in the size, amplitude, and energy, can arise at defects. It has been found that the large-amplitude inhomogeneity is a metastable formation. However, with inclusion of demagnetizing fields of the sample, it can become stable, i.e., energetically more favorable in comparison with the small-amplitude inhomogeneity. The possible contribution from this inhomogeneity to the static and dynamic processes of magnetization reversal of magnetic materials has been considered.

Description: This paper presents the results of investigations of the ordering of Jahn-Teller distorted MnO 6 octahedra in lightly doped single crystals of the composition La 1 − x Sr x MnO 3 (0.12 〈 x 〈 0.175) using the complex technique including measurements of elastic moduli and damping of high-frequency acoustic waves (700 MHz), electrical conductivity as a function of the temperature (100–400 K), and magnetic field ( H ≤ 1.5 T). The self-organization of the orbital, magnetic, and Jahn-Teller orderings and their influence on the transport, magnetic, and structural properties of lightly doped manganites have been investigated based on the analysis of the experimental results. The decisive influence of the local and cooperative Jahn-Teller orderings on the colossal magnetoresistance effect has been established.

Description: This paper presents the results of investigations of the structure, phase composition, and spectral-luminescent properties of Er 2 O 3 -doped zirconia crystals with different Y 2 O 3 concentrations: 99.7 mol % ZrO 2 -0.3 mol % Er 2 O 3 , 97.2 mol % ZrO 2 -1.0 mol % Y 2 O 3 -1.8 mol % Er 2 O 3 , 97.2 mol % ZrO 2 -2.0 mol % Y 2 O 3 -0.8 mol % Er 2 O 3 , 97.2 mol % ZrO 2 -2.5 mol % Y 2 O 3 -0.3 mol % Er 2 O 3 , 96.3 mol % ZrO 2 -3.4 mol % Y 2 O 3 -0.3 mol % Er 2 O 3 , and 86 mol % ZrO 2 -13.4 mol % Y 2 O 3 -0.6 mol % Er 2 O 3 . The transmission electron microscopy investigation has revealed the presence of twins in the 99.7 mol % ZrO 2 -0.3 mol % Er 2 O 3 crystals with a monoclinic structure and in the 97.2 mol % ZrO 2 -2.5 mol % Y 2 O 3 -0.3 mol % Er 2 O 3 and 96.3 mol % ZrO 2 -3.4 mol % Y 2 O 3 -0.3 mol % Er 2 O 3 crystals with a tetragonal structure. No twins have been found in the 86 mol % ZrO 2 -13.4 mol % Y 2 O 3 -0.6 mol % Er 2 O 3 crystals with a cubic structure. The phase composition of these crystals has been investigated using X-ray diffraction. It has been found that the 97.2 mol % ZrO 2 -1.0 mol % Y 2 O 3 -1.8 mol % Er 2 O 3 crystals contain only the transformable tetragonal phase t , whereas the 97.2 mol % ZrO 2 -2.0 mol % Y 2 O 3 -0.8 mol % Er 2 O 3 , 97.2 mol % ZrO 2 -2.5 mol % Y 2 O 3 -0.3 mol % Er 2 O 3 , and 96.3 mol % ZrO 2 -3.4 mol % Y 2 O 3 -0.3 mol % Er 2 O 3 crystals include two tetragonal phases with different degrees of tetragonality c / a : the transformable phase t and nontransformable phase t ′. Specific features of the formation of Er 3+ optical centers in zirconia crystals with different concentrations of stabilizing oxides have been revealed using the results of experiments on optical spectroscopy.

Description: The results of the experimental observation of the photovoltage in a SrTiO 3 crystal sample, which exhibits the light-induced resistance-drop effect, have confirmed the previously proposed model of the effect in its photoelectric part. However, in addition to the expected manifestation of the barrier photovoltage, one more source of photocurrent has been found. This source is attributed to the manifestation of the linear photogalvanic effect in the subsurface region of the crystal. It has been assumed that the main role in the generation of photogalvanic current can be played by dipole centers of the oxygen vacancy-triply charged titanium ion type, which are oriented by an electric field of the surface barrier.

Description: The results of investigations of the morphological properties of an oxide film formed on single-crystal silicon by anodic oxidation in distilled water in the potential-controlled mode have been presented. It has been established that the oxide film is always formed in the form of separate islands, the shape of which depends on the substrate orientation irrespective of the applied potential.

Description: The elastic hysteresis and residual deflections of samples made of steel 20, which correspond to the model of a thin rigid round plate pinched over the contour, have been investigated. It has been shown that annealing of the samples at 470 and 670 K weakly affects these characteristics, while after complete annealing (1170 K), the aging of steel 20 for three days is accompanied by a decrease in amplitude ω h of the elastic hysteresis by ∼20%. A postulate that there is no elasticity limit of metals, below which residual deformation would be absent, has been confirmed experimentally. It has been shown that, based on the values of ω h , the ultimate strength of metals can be estimated acting on the samples by stresses smaller than the yield stress by an order of magnitude. A giant increase (by a factor of ∼2.5) in ω h has been found after a prolonged (for 2 months) aging of steel 20 after the diffusion of hydrogen from it, which indicates the corresponding decrease in its cyclic longevity.

Description: A series of jumps of the magnetic moment (up to five jumps) with an amplitude of 1–10% of the saturation magnetization has been observed upon demagnetizing the molecular magnet [Mn{( R / S )- pn }] 2 [Mn{( R / S )- pn } 2 (H 2 O)][Cr(CN) 6 ] 2 in a narrow region of magnetic fields close to the coercive force. A decrease in the temperature leads to an increase in the critical magnetic field, which corresponds to the onset of the series of demagnetization jumps. The obtained experimental data agree with theoretical predictions on jump-like transitions between the magnetization curves upon attaining critical magnetic fields caused by the energy quantization of spin solitons.

Description: Magnetic properties of cobalt atoms in Au-Co chains on the Cu(110) surface (such as the magnetic moment, magnetic anisotropy energy, and exchange energy) have been calculated in the framework of the density functional theory. It has been found, at zero temperature, an infinitely long Au-Co chain is in the ferromagnetic state. The magnetostatic and magnetodynamic properties of finite-length Au-Co chains at a nonzero temperature have been investigated within the Heisenberg model using the kinetic Monte Carlo method. The dependences of the Curie temperature and magnetization reversal time on the chain length have been obtained, as well as the dependences of the coercivity of the chain on the temperature, chain length, and magnetization reversal rate.

Description: The influence of precipitation of germanium atoms in a solid solution on the dependence of the inelasticity characteristics on the germanium content in aluminum-germanium alloys prepared by directional crystallization has been studied. It has been shown that the Young’s modulus defect, the amplitude-dependent decrement, and the microplastic flow stress at a specified cyclic strain amplitude have extreme values at the eutectic germanium content in the alloy. The eutectic composition of the alloy undergoes a ductilebrittle transition. It has been found that there is a correlation between the dependences of the Young’s modulus defect, amplitude-dependent decrement, microplastic flow stress, and specific entropy of the exothermal process of germanium precipitation on the germanium content in the hypoeutectic alloy. The concentration dependences of the inelasticity characteristics and their changes after annealing have been explained by the change in the resistance to the motion of intragrain dislocations due to different structures of the Guinier-Preston zones formed during the precipitation of germanium atoms.

Description: The correlation of the electrical, magnetic, and structural properties of B i2 (Sn 1 − x Cr x ) 2 O 7 solid solutions has been investigated for two compositions with x = 0.05 and 0.1. The temperatures of structural phase transitions and anomalies of the electrical resistance in the vicinity of these transitions at temperatures in the range 300 K 〈 T 〈 1000 K have been determined using differential scanning calorimetry. It has been found that the thermoelectric power changes sign upon the polymorphic transition. The paramagnetic Curie temperature and the chromium-ion spin have been found from the temperature dependence of the magnetic susceptibility in the range 4 K 〈 T 〈 1000 K and from the field dependence of the magnetic moment in magnetic fields of up to 6 T.

Description: It has been shown experimentally that the thermal dissolution of silver and gold thin films in silicate glass is accompanied by the formation of a monolayer of silver and gold micro- and nanocrystals, respectively, on the surface of the glass. These processes occur at temperatures well below the melting temperature of the metal. Microcrystals are formed predominantly at the edges of islands of the metal film, where there is a sufficient amount of the material for their growth. Silver and gold nanocrystals are formed in the case when atoms of the metal dissolved in the glass repeatedly emerge on the glass surface. Silver and gold dissolved in the glass exist not only in the form of atoms and ions but also in the form of charged and neutral molecular clusters.

Description: Cooling of metallic glasses based on Pd and Zr from the supercooled liquid state with a low rate causes significant shear modulus and internal friction hystereses, which indicates a long relaxation time in the vicinity of the glass transition range. The nature of the observed phenomenon has been discussed within the interstitialcy theory.

Description: The effect of the linear approximation of the electronic spectrum of single-layer graphene (low-energy approximation) on the magnitude of charge transfer between an adatom and graphene has been investigated. It has been shown that the implementation of this approximation for adsorption of alkali metals and halogens leads to a change in the occupation numbers of local and band states as compared to the results obtained in the model taking into account the entire spectrum. However, the total occupation numbers agree quite well.

Description: The effect of pressure up to 22 GPa on the electrical resistance and thermopower of lanthanum monobismuthide at room temperature has been studied. A semiconductor-metal phase transition in the pressure range of 4–6 GPa has been revealed from the change in the sign of thermopower and the thermal dependence of the electrical resistance of LaBi. The observed inflections in the pressure dependences of the thermopower and electrical resistance of LaBi samples in the pressure range of 8–11 GPa can be ascribed to the structural phase transition from the B 1 phase to the PT and B 2 phases.

Description: Results of X-ray diffraction studies of shock-compressed single crystals indicate the rotation of crystallites by ∼3° ahead of the shock-wave front both in the plastic-flow and elastic-compression regions. Two dynamic states of the lattice have been detected. The brightness of reflections evolves with time. The position of the first dynamic reflection coincides with the position of a reflection from the initial structure. The second reflection corresponds to an equilibrium-compressed structure. Possible reasons of the formation of these two states of the lattice have been discussed.

Description: The growth and crystal structure of NiF 2 layers on CaF 2 /Si(111) heteroepitaxial substrates have been investigated. It has been shown that molecular beam epitaxy at temperatures of 350–450°C provides a stable epitaxial growth of the metastable orthorhombic NiF 2 phase (structural type CaCl 2 ) with a nickel fluoride layer thickness up to 1 μm in the metastable phase. According to X-ray diffraction, the unit cell parameters in layers of orthorhombic nickel fluoride are a = 4.5680(1) Å, b = 4.7566(3) Å, and c = 3.0505(2) Å, which are very close to the known values for this phase. It has been established that the condition \((100)_{NiF_2 } \left\| {(111)_{CaNiF_2 } } \right.\) holds over a wide range of growth parameters, which agrees with the results of the qualitative crystallographic analysis of the elements of similarity of the structures under consideration. The formation of a domain texture, the character of which depends on the growth temperature and nickel fluoride layer thickness, has been observed in the heterojunction plane.

Description: The problem of adsorption on amorphous single-layer graphene whose density of states is described by a simple analytic model has been considered. An analytic expression has been obtained for the density of states on the adatom. The estimations for the adsorption of H, K, Rb, and Cs show that the charge transfer from an adatom to the substrate in the case of the ideal single-layer graphene is higher than that in the case of amorphous graphene.

Description: A dislocation kinetic model of the formation and propagation of plastic shock waves in nanocrystalline materials (with a grain size of 1–100 nm) at pressures ranging from 1 to 50 GPa has been discussed theoretically. The model is based on a nonlinear equation of the reaction-diffusion type for the dislocation density, which includes the processes of multiplication, annihilation, and diffusion of dislocations with a strong absorption of the dislocations by nanograin boundaries. The solution of this equation is obtained in the form of a traveling dislocation density wave propagating with a constant velocity. The dependences of the dislocation density and dislocation front width on the nanograin size and pressure in the wave are determined. A comparison of the obtained dependences with the available results of the experiments and molecular dynamics simulations of shock-deformed nanocrystalline materials demonstrates their good quantitative agreement.

Description: The effect of the interface on the electrical resistance of graphene chemically deposited from the gas phase (CVD graphene) has been studied in the range from room temperature to the nitrogen boiling temperature. The resistance of a single-layer CVD graphene in the cases of its contacting with Si/SiO 2 and GaAs substrates demonstrates a nearly linear metallic temperature dependence with almost the same slope of the normalized curves. This slope corresponds to an increase in the graphene resistance by ~8% when graphene is heated from the boiling nitrogen temperature to room temperature. The four-layer graphene demonstrates a semiconducting temperature dependence in the same temperature range. It has been found that the sputtering of an organic insulator (parylene) on the four-layer graphene increases the slope of this dependence by ~5% and, at room temperature, increases the graphene resistance by ~20%.

Description: The ab initio calculation has been performed for the crystal structure and the phonon spectrum of titanates with the structure of pyrochlore R 2 Ti 2 O 7 ( R = Gd-Lu). The frequencies and types of fundamental vibrations have been found. For R = Tb, Tm, and Yb, this calculation has been carried out for the first time; furthermore, there is no available information on experimental studies of the phonon spectrum for Tm and Yb. The influence of hydrostatic pressure to 35 GPa on the structure, dynamics, and elastic properties of the Gd 2 Ti 2 O 7 lattice has been investigated. The dependence of the phonon frequencies on the pressure has been obtained. The calculations have predicted that the relative change in the pyrochlore structure volume during compression at pressures to 35 GPa is well described by the third-order Birch-Murnaghan equation of states. The results of the calculations agree with the available experimental data. It has been shown that the structural, dynamic, and elastic properties of the R 2 Ti 2 O 7 crystal lattice can be adequately described in the case where the inner shells of the RE ion up to 4 f are replaced by the pseudopotential.

Description: An analytical expression for the relaxation constant α in the Landau-Lifshitz-Hilbert equation has been derived using the semiclassical kinetic equation for the distribution function of magnons.

Description: The effect of constant magnetic fields on dislocation anharmonicity of p -type silicon single crystals with a conductivity of 6 Ω cm has been studied. It has been found that preliminary exposure of dislocation silicon (with a dislocation density of 10 4 –10 6 cm −2 ) to a constant magnetic field ( B = 0.7 T, t = 30 min) at room temperature causes a change in the nonlinear fourth-order elastic modulus β d . The observed changes are associated with the dynamics of magnetosensitive complexes of structural defects and, hence, with the changes in the length of the vibrating dislocation segment. Based on the dynamics of β d ( t ) after sample exposure to a magnetic field, the conclusion is made about an increase in the vibrating dislocation segment length L d by 30%, and the characteristic relaxation times of observed effects are estimated.

Description: The results of quantum-mechanical calculations of elementary prismanes—hexaprismane C 12 H 12 and octaprismane C16H16—have been presented. Their stability has been investigated in terms of the density functional theory and nonorthogonal tight-binding model, and the heights of potential barriers preventing isomerization and decay have been determined. It has been established based on the analysis of the molecular dynamics data and the hypersurface of the potential energy of these metastable compounds that hexaprismane and octaprismane have a rather high kinetic stability, which indicates the possibility of the formation of carbon polyprismanes for applications in microelectronics and nanoelectronics, power engineering, pharmaceutics, metrology, and information technologies.

Description: A radically new percolation model for describing the extremal dependence of the degree of reinforcement of polymer/carbon nanotube nanocomposites on the nanofiller content has been proposed. It has been shown that, for this nanofiller, the percolation threshold almost coincides with the aggregation threshold on the concentration scale. From the structural point of view, the extremum of this dependence is caused by the change in the type of the reinforcing component (from interphase regions to the skeleton of carbon nanotubes). From the mathematical point of view, the behavior of the degree of reinforcement is described by the general percolation relationship with replacement of the critical exponents near the percolation threshold. Neither the functionalization of the nanofiller nor the preliminary ultrasound treatment qualitatively change the dependence under study.

Description: The results of ab initio calculations of the ferroelectric and magnetic properties of the recently synthesized double perovskites LaPb Me SbO 6 ( Me 2+ = Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ ) have been presented. The ordered double perovskites with a layered ordering of cations A and A ′ and a checkerboard ordering of cations B and B ′ have been considered. The calculation of the lattice dynamics has revealed instabilities in the phonon spectra of the high-symmetry phase of these compounds. The condensation of unstable modes leads to a stable polar phase P 2 1 . The spontaneous polarization in this phase is found to be ~30 μC/cm 2 . The magnetic ground state is antiferromagnetic with an antiparallel direction of the magnetic moments in adjacent planes along the [001] direction. The Néel temperatures are estimated in the mean field approximation. The presence of the ferroelectric and magnetic order parameters in the structure suggests that the studied double perovskites with the simultaneous ordering of the cations are potential multiferroics.

Description: The Bethe approximation as applied to a system consisting of magnetic and nonmagnetic atoms in the thermodynamic equilibrium has been considered. In this approximation, the dependences of the magnetization and Curie temperature on the concentration of magnetic atoms for the Ising model with mobile nonmagnetic impurities have been constructed and the limiting concentrations of the appearance of spontaneous magnetization in the ground state have been obtained. It has been established that the considered approximation for a one-dimensional chain is the exact solution.

Description: The effects of the interaction of ultrasound with donor d electrons of cobalt impurity atoms at low concentrations in mercury selenide crystals have been investigated. The temperature dependences of the electronic contribution to the absorption coefficient at a frequency of 53 MHz in crystals with cobalt concentrations from 10 18 to 10 20 cm −3 and in the undoped crystal have been observed experimentally. It has been found that crystals with impurities are characterized by an anomalous nonmonotonic temperature dependence of the absorption coefficient of the slow transverse wave in a narrow temperature range near 10 K. A smooth monotonic temperature dependence has been observed for longitudinal and fast transverse waves. Based on the developed theoretical interpretation, it has been established that the anomaly in the temperature dependence of the absorption coefficient of a slow transverse wave is associated with the hybridization of impurity d states in the conduction band of the crystal. A comparison of the theoretical and experimental dependences has made it possible to determine the parameters characterizing the hybridized electronic states.

Description: The effect of the accelerating voltage U of the SEM electron beam on the characteristics of microdomains recorded by the electron beam method on the nonpolar Y -surface of LiNbO 3 crystals has been studied. The thickness T d of domains in the Y direction is determined by the depth range R e of primary electrons, which depends on U . This makes it possible to define T d in the range of 0.2–4 μm at U = 5–25 kV, respectively. The electron emission coefficient σ is estimated for different values of U exceeding the second equilibrium point U 2 (σ = 1) in the σ( U ) diagram. These data are used to construct the dependence σ( U ) for LiNbO 3 . Based on the exposure characteristics of the length L d of domains growing along the polar Z axis, the dependence of the space charge field controlling the domain planar growth along Z on the surface electron emission σ is found.

Description: It has been found that the phase with the fcc lattice of the NaCl structural type is formed due to the vacuum-arc deposition of the nanostructured multicomponent (TiZrHfVNbTa)N coating. Implantation of negative Au − ions with a dose of 1 × 10 17 cm −2 leads to the formation of a disordered polycrystalline structure without a preferred orientation of the fcc phase and nanocrystallites from 5–7 to 1–3 nm is size, which are dispersed in a layer up to 35 nm in depth. Nanohardness increases to 33 GPa, and the Vickers hardness reaches 51 GPa. Gold nanoclusters are formed in the near-surface region, while the fcc lattice and the formation of local Au regions are observed in the coating itself. Fragments with the hcp lattice are formed at depths above 180 nm because of the low nitrogen concentration.

Description: Based on the numerical solution of Landau-Lifshitz equations, the nonlinear dynamic behavior of vortex-like domain walls in films with in-plane anisotropy has been investigated in external magnetic fields H significantly exceeding critical fields H c , above which the stationary motion of domain walls is replaced by nonstationary (periodic or aperiodic) motion. A method has been proposed for the detection of complex aperiodic dynamics of structural rearrangements of domain walls, which is based on the construction of diagrams of the dependences of the tilt angle of the magnetization M with respect to the plane of the domain wall in some of its points on the corresponding angle in other points. It has been found that these diagrams significantly change with variations in the external magnetic field applied along the easy axis of magnetization in the range H 〉 H c . It has been shown that the pattern of these changes is similar to the scenario of the Feigenbaum transition to dynamic chaos.

Description: The correlation between the heat capacities of rare-earth cuprates, orthovanadates, and garnets with ionic radius R 3+ has been analyzed. It has been shown that the values of C p 0 change consistently depending on the radius R 3+ within the corresponding tetrads (La-Nd, Pm-Gd, Gd-Ho, Eu-Lu).

Description: Relaxation processes in side-chain liquid-crystal azomethine polymer have been studied using dielectric spectroscopy in wide ranges of temperatures and frequencies. Two low-temperature relaxation processes (β 1 and β 2 ) caused by low-amplitude noncooperative motion of kinetic units in side groups and a high-temperature α-process caused by the large-scale cooperative motion of kinetic units in the main polymer chain have been revealed.

Description: The incorporation of fluorine atoms into the silicon dioxide lattice upon F + ion implantation and the formation of silicon (germanium) nanocrystals in SiO 2 upon Si + (Ge + ) ion implantation have been numerically simulated. The calculations for F have been performed by the density functional theory (DFT) method; the calculations for Si and Ge have been carried out by combining the DFT (in the cluster approximation) and Monte Carlo methods. The energy gain of the fluorine atom attachment to one of silicon atoms with the formation of a nonbridging oxygen hole center (NBOHC) and an energy level appearing in the band gap has been demonstrated. In the case of ion implantation, the simulation at a dissolved Si (Ge) atom concentration of ∼2 at % has revealed the formation of nanocrystals (NCs) with an average size of ∼1 nm.

Description: The current density in a superlattice exposed to a quantizing electric field and the terahertz field has been calculated. The calculations have been carried out taking into account inelastic scattering of charge carriers by phonons. The possibility of an absolute negative conductivity, i.e., the emergence of electric current opposing the direction of the quantizing electric field, has been demonstrated.

Description: For the first time, zinc oxide epitaxial films on silicon were grown by the method of atomic layer deposition at a temperature T = 250°C. In order to avoid a chemical reaction between silicon and zinc oxide (at the growth temperature, the rate constant of the reaction is of the order of 10 22 ), a high-quality silicon carbide buffer layer with a thickness of ~50 nm was preliminarily synthesized by the chemical substitution of atoms on the silicon surface. The zinc oxide films were grown on n - and p -type Si(100) wafers. The ellipsometric, Raman, electron diffraction, and trace element analyses showed that the ZnO films are epitaxial.

Description: A technique for the evaluation of the electron work function of metallic single crystals and the electron work function anisotropy has been developed in the framework of the electron-statistical method. The surface energy and the electron work function have been calculated for crystal faces of allotropic modifications of 4 d - and 5 d -metals. A change in the electron work function due to the allotropic transformations has been estimated, and the periodic dependence of the electron work function has been determined. It has been shown that the results obtained using the proposed technique correlate with the available experimental data for polycrystals.

Description: It has been experimentally shown that a longitudinal thermal-diffusion autosoliton, which is generated in a nonequilibrium electron–hole plasma in p -InSb, in an external longitudinal magnetic field acquires diamagnetic properties. The results of the calculation and numerical estimates of the diamagnetism have been presented.

Description: Based on the free energy density functional method, the early stage of decomposition of a onedimensional binary alloy corresponding to the approximation of regular solutions has been simulated. In the simulation, Gaussian composition fluctuations caused by the initial alloy state are taken into account. The calculation is performed using the block approach implying discretization of the extensive solution volume into independent fragments for each of which the decomposition process is calculated, and then a joint analysis of the formed second phase segregations is performed. It was possible to trace all stages of solid solution decomposition: nucleation, growth, and coalescence (initial stage). The time dependences of the main phase distribution characteristics are calculated: the average size and concentration of the second phase particles, their size distribution function, and the nucleation rate of the second phase particles (clusters). Cluster trajectories in the size–composition space are constructed for the cases of growth and dissolution.

Description: A dynamic model has been proposed for describing the extrusion of a single layer of a liquid-crystal (LC) material into a meniscus from an N -layer circular free-standing smectic film (FSSF). In the framework of this model, the main mechanism responsible for the process of the thinning (extrusion) of the LC material from the N -layer FSSF is based on the appearance of a spatial pressure gradient directed along the radius of the circular FSSF. This gradient is formed due to the difference in the disjoining pressures on both sides of the front separating the N - and ( N –1)-layer domains of the smectic film. The proposed model allows taking into account the influence of the meniscus on dynamic characteristics, such as the time required for the complete extrusion of a single layer from the N -layer FSSF and the velocity of propagation of the front separating the N - and ( N –1)-layer domains in the process of the thinning of the smectic film formed by molecules of 5- n -alkyl-2-(4- n -(perfluoroalkyl-methyleneoxy))pentyl.

Description: Oxide compounds Pr 2 Sn 2 O 7 and Nd 2 Sn 2 O 7 have been obtained by solid-phase synthesis. The effect of temperature on the heat capacity of Pr 2 Sn 2 O 7 (360–1045 K) and Nd 2 Sn 2 O 7 (360–1030 K) has been studied using differential scanning calorimetry. The thermodynamic properties of the compounds (changes in enthalpy, entropy, and the reduced Gibbs energy) have been calculated by the experimental data of C p = f ( T ).

Description: The phonon spectra in thin layers of bismuth telluride and solid solutions of Bi 2– x Sb x Te 3– y Se y of different composition, belonging to three-dimensional topological insulators, have been investigated by micro-Raman spectroscopy, and the morphology of an interlayer van der Waals (0001) surface in them has been studied by semicontact atomic force microscopy at room temperature. The analysis of the Raman spectra and the intensity ratio of active and inactive longitudinal optical modes depending on the composition, morphology of the interlayer surface, and thickness of the layers enabled the estimation of the effect of topological surface states of Dirac fermions, associated with the strengthening of the electron–phonon interaction as a result of resonance Raman scattering, and the identification of the compositions, in which the contribution of topological surface states becomes dominant.

Description: The irradiation of metallic films by a nanosecond pulsed laser leads to a self-assembly of nanoparticle arrays. This method has been used to prepare bimetallic Au/Co nanoparticles on a SiO 2 substrate. The microstructure and morphology of the bimetallic nanoparticles have been investigated using scanning electron microscopy and transmission electron microscopy. It has been shown that the bimetallic nanoparticles have a hemispherical shape with a single-crystal structure and an average size of ~50 nm. The magnetic properties of these nanoparticles have been examined using a vibrating-sample magnetometer in the transverse and longitudinal directions. It has been found that the direction of the magnetization of the bimetallic nanoparticles lies in the plane of the substrate, and the coercive forces in the transverse and longitudinal directions differ by 25%. The use of the vibrating-sample magnetometer method makes it possible to investigate the differences in the magnetic saturations and the coercive forces of an array of bimetallic nanoparticles on a large surface area. The performed investigations have demonstrated that the anisotropic nanomagnetic materials with the desired magnetic orientation can be easily and quickly prepared by means of thermal laser treatment.

Description: Thin films of partially deuterated betaine phosphate have been grown by the evaporation on Al 2 O 3 (110) and NdGaO 3 (001) substrates with a preliminarily deposited structure of interdigitated electrodes. The grown films have a polycrystalline block structure with characteristic dimensions of blocks of the order of 0.1–1.5 mm. The degree of deuteration of the films D varies in the range of 20–50%. It has been found that, at the antiferroelectric phase transition temperature T c afe = 100–114 K, the fabricated structures exhibit an anomaly of the electrical capacitance C , which is not accompanied by a change in the dielectric loss tangent tanδ. The strong-signal dielectric response is characterized by the appearance of a ferroelectric nonlinearity at temperatures T 〉 T c afe , which is transformed into an antiferroelectric nonlinearity at T 〈 T c afe . With a further decrease in the temperature, double dielectric hysteresis loops appear in the antiferroelectric phase. The dielectric properties of the films have been described within the framework of the Landau-type thermodynamic model taking into account the biquadratic coupling ξ P 2 η 2 between the polar order parameter P and the nonpolar order parameter η with a positive coefficient ξ. The E–T phase diagram has been constructed.

Description: The magnetic state of a system of particles with a “large” spin of 3/2 in the presence of isotropic exchange interaction in the system has been studied on the basis of a derived spin Hamiltonian. It has been shown that, at a positive contribution of the exchange interaction, an unstable nematic state appears and transforms to a stable ferromagnetic state (with an average spin of 3/2). The excitation spectrum in the ferromagnetic state is a triply degenerate Goldstone-type gapless magnon mode. At a negative sign of the exchange contribution, an antinematic state is stable with respect to a transition to a ferromagnetic state, which is forbidden. In this case, the antinematic always occurs in the state of a phase transition to an unstable antiferromagnetic state, the excitation spectrum of which is characterized by a single nondegenerate Goldstone mode.

Description: Photonic structures with hexagonal symmetry have been prepared by the additive technology of two-photon laser lithography, and their optical properties have been investigated. The structure of the samples has been examined using scanning electron microscopy. The calculations have been performed for the optical diffraction in the Born approximation of the scattering theory for structures with a limited number of scatterers. The images formed in the monochromatic light on a flat screen located behind the sample have been calculated. The diffraction patterns on the screen have C 6 v symmetry and consist of three straight lines intersecting at an angle of 120° and hyperbolas, the number of which is a multiple of six. An important feature of these diffraction patterns is the superstructure, i.e., the partition of straight lines and hyperbolas into individual diffraction reflections, the number of which is determined by the number of scatterers of a particular sample. The results of the experimental investigation of the diffraction patterns completely coincide with the calculated data, including the number and arrangement of the superstructure reflections.

Description: The micromagnetic structure of the domain wall (DW) with periodically distributed horizontal Bloch lines in a ferromagnetic film in an external electric field has been studied. The effect of the electric field on the internal DW micromagnetic structure is caused by inhomogeneous magnetoelectric coupling. Possible scenarios of the DW internal structure transformations implemented with varying the electric fields strength have been analyzed in detail. For each scenario, static characteristics of the system, such as the energy, DW profile, DW effective thickness, and electric polarization have been calculated.

Description: This paper reports on the results of the investigation into the magnetocaloric properties of sandwich structures of La 1– x K x MnO 3 manganites with x = 0.11 (LKM11), 0.13 (LKM13), and 0.15 (LKM15) in magnetic fields of up to 18 kOe. The results of the analysis of the field and temperature dependences of the magnetocaloric effect in the structures LKM11 + LKM13 and LKM13 + LKM15 have demonstrated that the use of sandwich structures increases the efficiency of magnetic cooling in a magnetic field of 18 kOe by 45%.

Description: The Potts model of a diluted magnet with an arbitrary number of states placed in the external field has been considered. Phase transitions of this model have been studied in the mean-field approximation, the dependence of the critical temperature on the external field and the density of magnetic atoms has been found, and the magnetic susceptibility has been calculated. An improved mean-field technique has been proposed, which provides more accurate account of the effects associated with nonmagnetic dilution. The influence of dilution on the first-order phase transition curve and the magnetization jump at the phase transition has been studied by this technique.

Description: The recrystallization of the structure of an X-ray amorphous AlN–TiB 2 –TiSi 2 coating containing short-range order regions with characteristic sizes of 0.8–1.0 nm has been performed using a negative gold ion (Au – ) beam and high-temperature annealing. Direct measurements using methods of high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectral (EDXS) microanalysis have demonstrated that thermal annealing at a temperature of 1300°C in air results in the formation of nanoscale (10–15 nm) phases AlN, AlB 2 , Al 3 O 3 , and TiO 2 , whereas the ion implantation of negative ions Au – leads to a fragmentation (decrease in the size) of nanograins to 2–5 nm with the formation of spheroidal gold nanocrystallites a few nanometers in size, as well as to the formation of an amorphous oxide film in the depth (near-surface layer) of the coating due to ballistic ion mixing and collision cascades.

Description: The thermal diffusion, heat capacity, and thermal conductivity of BiFeO 3 , Bi 0.91 Nd 0.09 FeO 3 , and BiFe 0.91 Mn 0.09 O 3 multiferroics have been studied at high temperatures (300–1120 K). The dominant mechanisms of phonon transfer in the regions of the antiferromagnetic and ferroelectric phase transitions have been determined. The temperature dependence of the mean free path of phonons has been found.

Description: Scrolled packings of single-layer and multilayer graphene can be used for the creation of supercapacitors, nanopumps, nanofilters, and other nanodevices. The full atomistic simulation of graphene scrolls is restricted to consideration of relatively small systems in small time intervals. To overcome this difficulty, a two-dimensional chain model making possible an efficient calculation of static and dynamic characteristics of nanoribbon scrolls with allowance for the longitudinal and bending stiffness of nanoribbons is proposed. The model is extended to the case of scrolls of multilayer graphene. Possible equilibrium states of symmetric scrolls of multilayer carbon nanotribbons rolled up so that all nanoribbons in the scroll are equivalent are found. Dependences of the number of coils, the inner and outer radii, lowest vibrational eigenfrequencies of rolled packages on the length L of nanoribbons are obtained. It is shown that the lowest vibrational eigenfrequency of a symmetric scroll decreases with a nanoribbon length proportionally to L –1 . It is energetically unfavorable for too short nanoribbons to roll up, and their ground state is a stack of plane nanoribbons. With an increasing number k of layers, the nanoribbon length L necessary for creation of symmetric scrolls increases. For a sufficiently small number of layers k and a sufficiently large nanoribbon length L , the scrolled packing has the lowest energy as compared to that of stack of plane nanoribbons and folded structures. The results can be used for development of nanomaterials and nanodevices on the basis of graphene scrolled packings.

Description: The strontianite (SrCO 3 )–witherite (BaCO 3 ) solid solutions have been simulated using the interatomic potential method. The dependences of the unit cell parameters, the unit cell volume, and the bulk modulus on the composition of the solid solution have been constructed. It has been shown that the unit cell volume and the bulk modulus exhibit negative deviations from the additivity. An analysis of the local structure of the solid solutions has been carried out. It has been found that, for the equimolar composition of the Ba x Sr 1– x CO 3 solid solution, the relaxations of the barium and strontium positions are equal to 60 and 56%, respectively. It has been established that the enthalpy of mixing is positive and, for the equimolar composition of the solid solution, reaches a maximum value of 3.4 kJ/mol. The obtained results have been compared with the experimental data. The solvus of the Ba x Sr 1– x CO 3 system has been constructed based on the dependences of the Gibbs free energy on the composition in the temperature range from 300 to 1000 K.

Description: A method has been proposed for the formation of three-dimensional arrays of isolated magnetic clusters NiO, Co 3 O 4 , and NiCo 2 O 4 in the sublattice of pores in the matrix of bulk synthetic opals through a single impregnation of the pores with melts of nickel and cobalt nitrate crystal hydrates and their thermal degradation. The method makes it possible to controllably vary the degree of filling of pores in the matrix with oxides within 10–70 vol %. The composition and structure of the synthesized materials, as well as the dependences of their static magnetic susceptibility on the magnetic field strength, have been investigated.

Description: The crystal structure and phonon spectrum of PrFe 3 (BO 3 ) 4 are ab initio calculated in the context of the density functional theory. The ion coordinates in the unit cell of a crystal and the lattice parameters are evaluated from the calculations. The types and frequencies of the fundamental vibrations, as well as the line intensities of the IR spectrum, are determined. The elastic constants of the crystal are calculated. A “seed” frequency of the vibration strongly interacting with the electron excitation on the praseodymium ion is obtained for low-frequency A 2 mode. The calculated results are in agreement with the known experimental data.

Description: The EPR spectra of a system of two coupled spins with strongly anisotropic g factors have been calculated. It has been shown that the spectra can exhibit an additional absorption line in the vicinity of the energy level anticrossing. The emergence of this line is caused by strengthening of the off-resonance absorption in the anticrossing region.

Description: The results of the experimental investigation of the thermoelectric power and electrical conductivity of amorphous and nanocrystalline films in the Cr 1– x Si x (0.65 〈 x 〈 0.89) system at temperatures ranging from 300 to 800 K have been presented. It has been shown that the amorphous films rapidly crystallize at temperatures above 550 K. During the crystallization, the amorphous films transform into the nanocrystalline state. The rate of crystallization rapidly decreases with a decrease in the temperature. The in situ measurements of the thermoelectric power and electrical resistivity of the CrSi 2 film have been performed during isothermal annealing at a temperature of 496 K. It has been demonstrated that the crystallization leads to an additional contribution to the thermoelectric power due to selective scattering of charge carriers at the boundaries of the nanocrystals.

Description: The results of the investigation of the electronic structure of the conduction band in the energy range 5–25 eV above the Fermi level E F and the interfacial potential barrier upon deposition of aziridinylphenylpyrrolofullerene (APP-C 60 ) and fullerene (C 60 ) films on the surface of the real germanium oxide ((GeO 2 )Ge) have been presented. The content of the oxide on the (GeO 2 )Ge surface has been determined using X-ray photoelectron spectroscopy. The electronic properties have been measured using the very low energy electron diffraction (VLEED) technique in the total current spectroscopy (TCS) mode. The regularities of the change in the fine structure of total current spectra (FSTCS) with an increase in the thickness of the APP-C 60 and C 60 coatings to 7 nm have been investigated. A comparison of the structures of the FSTCS maxima for the C 60 and APP-C 60 films has made it possible to reveal the energy range (6–10 eV above the Fermi level E F ) in which the energy states are determined by both the π* and σ* states and the FSTCS spectra have different structures of the maxima for the APP-C 60 and unsubstituted C 60 films. The formation of the interfacial potential barrier upon deposition of APP-C 60 and C 60 on the (GeO 2 )Ge surface is accompanied by an increase in the work function of the surface E vac – E F by the value of 0.2–0.3 eV, which corresponds to the transfer of the electron density from the substrate to the organic films under investigation. The largest changes occur with an increase in the coating thickness to 3 nm, and with further deposition of APP-C 60 and C 60 , the work function of the surface changes only slightly.

Description: The magnetic susceptibility, electrical resistivity, and thermoelectric power of Ti 50 Ni 50‒ x Cu x alloys with copper concentrations x ⩽ 25 at % have been measured in the temperature range of 2–500 K. The change in the electronic band structure near the Fermi level upon thermoelastic martensitic transformations, such as B 2 ↔ B 19′, B 2 ↔ B 19 ↔ B 19′, and B 2 ↔ B 19, has been considered.

Description: The previously published photoluminescence spectra of bulk germanium single crystals with orientations (100), (110), and (111) under different biaxial tensile strains have been investigated using the differential method proposed by the author for the analysis of luminescence spectra of semiconductors. An increase in the strain for all these orientations of the single crystals leads to a shift in the maxima of the differential spectra in the region of direct radiative transitions toward lower photon energies due to the narrowing of the germanium direct band gap. At the same time, the positions of the maxima of the differential spectra in the region of indirect radiative transitions remain almost unchanged. This indicates that the germanium indirect band gap does not depend on the tensile strains, at least for their values of ∼0.2–0.3%.

Description: A theoretical model that effectively describes the nucleation of cracks in stress fields of dislocation pile-ups near the free surface in metallic nanomaterials with a bimodal structure has been developed. The dependences of the critical shear stress τ c (for the formation of a crack with an equilibrium length of 10 nm on a dislocation pile-up near the surface) on the size d of a grain containing the dislocation pile-up have been calculated for copper with a bimodal structure. Theoretically, it has been found that the critical shear stress τ c for the nucleation of a crack near the free surface in a nanomaterial with a bimodal structure is approximately 30% higher than that for the crack nucleation within the nanomaterial at a distance from the free surface.

Description: It has been found that CoFeB–SiO 2 /C and CoFeB–SiO 2 /Bi 2 Te 3 multilayer heterostructures with a cluster structure of CoFeB layers feature a long-range magnetic order in the entire temperature range from 2 to 300 K. At high temperatures ( T = 300 K), CoFeB clusters exhibit magnetic properties characteristic of superparamagnets. At low temperatures ( T = 5 K), clusters are ferromagnetic, and the easy magnetization axis is in the film plane. The temperature of the ferromagnetic-to-superparamagnetic state transition of clusters depends on a dielectric interlayer material: the use of Bi 2 Te 3 instead of C as a spacer layer leads to an increase in the transition temperature by a factor of 4 and an increase in the magnetization blocking temperature of CoFeB clusters in a field of 100 Oe by a factor of 3.

Description: A method of surface curvature of carbon nanotubes has been proposed for quantitative estimation of the longitudinal conductivity of nanotubes. A dispersion relation for the electron spectrum of single-walled carbon nanotubes has been obtained analytically. The change in the zone structure of nanotubes of various types and diameters caused by taking into account the surface curvature has been analyzed. The temperature dependence of the longitudinal component of conductivity with allowance for the surface curvature for a series of nanotubes has been calculated. The comparison with the conductivity of a plane graphene has been performed. It has been shown that, in zig-zag tubes, the correction of the conductivity for the surface curvature decreases with an increase in temperature as well as with an increase in the radius of curvature.

Description: The capacitance and dielectric loss tangent of Gd x Mn 1– x S ( x ≤ 0.2) solid solutions have been measured at a frequency of 10 kHz without magnetic field and in a magnetic field of 8 kOe in the temperature range of 90–450 K. An increase in the permittivity and a dielectric loss maximum have been detected in the low-temperature region. It has been found that the temperature of the maximum of the imaginary part of the permittivity shifts to higher temperatures with increasing concentration. The magnetocapacitance effect has been revealed for two compositions. The dielectric loss has been described in the Debye model with “freezing” dipole moments and in the orbital-charge ordering model.

Description: The conditions (regimes of deposition and thermal treatment) for gas bubble formation in ferroelectric Pb(Ti 1– y Zr y )O 3 films have been determined by thermal desorption and electron and optical micros-copy. A mechanism of bubble formation has been proposed. This mechanism rests upon the notion that lead can form oxides of the PbO 2 type with a high oxygen content at relatively low temperatures and that these oxides break down with the release of oxygen to lower oxides of the PbO type upon subsequent heating. These ideas have been taken as the basis of a technique for the fabrication of Pb(Ti 1– y Zr y )O 3 films with a reduced (by an order of magnitude) density of through defects.

Description: It has been revealed for the first time that the introduction of excess manganese to a charge when preparing nanometer-sized manganite powders exhibiting the colossal magnetoresistance effect leads to the formation of a single-phase material with the crystallite sizes 15–25 nm that are two time smaller than those in manganite powders produced without excess manganese.

Description: The integrated intensity of X-ray diffraction reflections has been measured for a series of epitaxial layers of AIII nitrides (GaN, AlN, AlGaN) grown on different substrates (sapphire, SiC) and characterized by different degrees of structural perfection. It has been shown that, despite a high density of dislocations and a significant broadening of the diffraction peaks, the obtained values are not described by the kinematic theory of X-ray diffraction and suggest the existence of extinction. The results have been analyzed on the basis of the Darwin and Zachariasen extinction models. The secondary extinction coefficients and the thicknesses of epitaxial layers have been determined using two orders of reflection both in the Bragg geometry (0002 and 0004) and in the Laue geometry ( \(10\bar 10\) ) and \(10\bar 20\) ). It has been demonstrated that the secondary extinction coefficient is the greater, the smaller is the broadening of the diffraction peaks and, consequently, the dislocation density. It has been found that, for epitaxial layers with a regular system of threading dislocations, the secondary extinction coefficient for the Laue reflections is substantially greater than that for the Bragg reflections.

Description: A mechanism of decrease in the elastic (latent) energy of a solid containing disclination defects by introducing multi-disclination configurations of opposite sign has been considered. The relation of the proposed model with relaxation modifications of microcrystals with pentagonal symmetry, as well as with the structure of two-dimensional carbon films, has been discussed. An approach to the prediction of new carbon structures inherently containing multi-disclination configurations with screening has been demonstrated.

Description: The magnetic properties of nonstoichiometric lanthanum manganites La 1– x Mn 1– y O 3 have been studied in the temperature range 80 K 〈 T 〈 650 K. The Curie temperature T C changes nonmonotonically as the number of Mn 4+ ions increases. In the paramagnetic region, there exist isolated Mn ions and magnetic polarons which can be conserved to T ⩽ 4 T C , independent of the lattice symmetry. In the T C 〈 T 〈 T pol region, the temperature dependences of the magnetic susceptibility are nonlinear and can be described by the Curie law with a temperature-dependent Curie constant C . The sample has been prepared having a composition near the O′ → O structural transition; the spontaneous magnetization of the sample at T ⩽ 1.6 T C is associated to correlated polarons forming due to the double exchange in chains of the E -type antiferromagnetic phase.

Description: The dielectric spectra of Pb 1– x Ba x (Mg 1/3 Nb 2/3 ) m (Zn 1/3 Nb 2/3 ) y (Ni 1/3 Nb 2/3 ) n Ti z O 3 ( x = 0–0.15, m = 0.4541, y = 0.0982, n = 0.1477, and z = 0.3) ceramic samples have been studied in wide intervals of temperature (10–873 K) and frequency of the measurement electric field (0.1–1000 kHz). It has been found that an increase in the Ba 2+ ( x ) content leads to a reduction in the phase transition temperature (from 418 K at x = 0 to 256 K at x = 0.15), to the transition from the normal ferroelectric state to the relaxor ferroelectric one (at x ≥ 0.025), and to the disappearance of temperature hysteresis of dependences of the relative dielectric permittivity. It has been hypothesized that a tricritical point is present near x ∼ 0.125 in the x–T phase diagram of the studied solid solutions.

Description: The influence of spin fluctuations on the magnetic properties of the ferromagnetic helimagnet MnSi has been studied in the Hubbard model taking into account the antisymmetric relativistic Dzyaloshinskii–Moriya interaction for band electrons. The obtained equations of the magnetic state indicate the correlation between the fine structure of the density of electronic states and the magnetization and coefficient of mode–mode coupling. It has been shown that the position of the Fermi energy in the immediate proximity on the point of the local minimum of the density of electronic states leads to large zero spin fluctuations at low magnetization of the helimagnet. When approaching from down the Néel point (approximately, at 0.9 T N ), the zero fluctuation disappear, and the temperature rise of thermal spin fluctuation is accompanied by the change in the sign of the coefficient of mode–mode coupling. A magnetic field perpendicular to the helicoids plane brings about the formation and subsequent “collapse” of the helimagnetic cone. However, the condition of the change in the sign of the coefficient of mode–mode coupling divides the MnSi phase diagram into two parts, one of which corresponds to the ferromagnetic state induced by the field, and the other corresponding to the paramagnetic state. In this case, the h–T diagram has a specific region, inside which the paramagnetic and the ferromagnetic state are instable. The boundaries of the region agree with the experimental data on the boundaries of the anomalous phase ( a phase). It has been found that the results of calculations of the temperature dependence of the magnetic susceptibility agree with the experimental data.

Description: Intercalation of graphene on Ir (111) with Sm atoms is studied by methods of thermal desorption spectroscopy and thermionic emission. It is shown that adsorption of samarium at T = 300 K on graphene to concentrations of N ≤ 6 × 10 14 atoms cm –2 followed by heating of the substrate leads to practically complete escape of adsorbate underneath the graphene layer. At N 〉 6 × 10 14 atoms cm –2 and increasing temperature, a fraction of adsorbate remains on graphene in the form of two-dimensional “gas” and samarium islands and are desorbed in the range of temperatures of 1000–1200 K. Samarium remaining under the graphene is desorbed from the surface in the temperature range 1200–2150 K. Model conceptions for the samarium–graphene–iridium system in a wide temperature range are developed.

Description: Two-phase composites x La 0.7 Sr 0.3 MnO 3 /(100– x )C ( x = 5–85 mass %) have been synthesized. The magnetoresistive properties of these materials in magnetic fields from 0 to 15 kOe have been investigated. It has been shown that, at room temperature, the positive isotropic magnetoresistance for samples with x = 50–60 mass % reaches 15%.

Description: Metastable solid solutions (SS) Mn 3 FeTiSbO 9 and Mn 4 FeTi 2 SbO 12 with the ilmenite structure (space group R \(\bar 3\) ) have been prepared by quenching at normal conditions. The compositions of the compounds have been justified using EDX spectroscopy and X-ray diffraction. The magnetic properties of SSs have been analyzed by comparison with ferrimagnetic ilmenite Mn 2 FeSbO 6 ( T N = 269 K) as a natural mineral and ceramics obtained at high pressure and high temperature. The solid solutions have been characterized as dilute magnetic systems formed as a result of substitution of nonmagnetic cations Ti 4+ for a part of Fe 3+ and Sb 5+ cations. Mn 3 FeTiSbO 9 is considered as a ferromagnetic with T N = 171 K and Mn 4 FeTi 2 SbO 12 as a magnetic with the concentration of magnetic clusters below the percolation threshold.

Description: This paper reports on the results of measurements of changes in the temperature of a solid under the adiabatic elastic loading (thermoelastic effect), the coefficient of thermal expansion, and the Young’s modulus of a rigid-chain vitrified polymer, namely, polyimide. It has been found that there are differences in the sign and magnitude of the changes in the energy of thermal origin in samples and the work of the external force. The energy of the thermoelastic effect has been explained in terms of the influence exerted by the anharmonic expansion of a solid, with the separation of the quasi-static potential and dynamic components of the thermal energy of the solid. The loading with an external force causes a redistribution of the thermal energy. A change in the temperature of the solid corresponds to a change in the dynamic component. An energy analysis of the adiabatically loaded anharmonic oscillator has confirmed the conclusion regarding the mechanism of energy transfer and revealed that, under loading, there is a redistribution of the kinetic and potential components of the internal energy of the oscillator.

Description: X-ray diffraction patterns and nuclear gamma resonance spectra of La(Fe 0.88 Si x Al 0.12 − x ) 13 compounds in the paramagnetic state at room temperature have been investigated. It has been found that all samples have a cubic structure of the NaZn 13 type, in which Si and Al atoms disorderly substitute for iron in the crystallographic position 96 i . An analysis of the Mössbauer spectra using the fitting with doublets with different quadrupole splittings has revealed that the distributions of the aluminum and silicon impurity atoms substituting for iron differ significantly. Aluminum is statistically distributed over nine positions of the 96 i type in the generalized coordination sphere of the Fe2 atom, whereas silicon predominantly substitutes for only six of the nine positions.

Description: The influence of the granule size on the magnetic and magnetocaloric properties of ceramic sample of manganite La 0.5 Ca 0.5 MnO 3 has been investigated. Anomalies indicating the coexistence of the ferromagnetic metallic and antiferromagnetic charge-ordered phases below T C have been found in the temperature dependence of the magnetocaloric effect. It has been shown that a decrease in the granule size to 90 nm leads to the complete suppression of the antiferromagnetic charge-ordered phase.

Description: The results of the influence of the isotopic substitution of oxygen 16 O → 18 O on the susceptibility, electrical resistance, heat capacity, and the magnetocaloric effect in univalently doped manganite La 0.8 Ag 0.1 MnO 3 are presented. It has been shown that the substitution of 16 O by a heavier isotope 18 O leads to a shift in T C and affects all the measured coefficients. This result indicates the necessity of accounting the lattice dynamics when explaining the mechanism of colossal magnetoresistance in manganites.

Description: The optical and electrical properties of light-emitting diode structures with an active layer based on nanocomposite polyvinylcarbazole (PVK) films doped with nanoparticles of another light-emitting polymer, MEH-PPV, have been studied. It has been established that the size of MEH-PPV particles in the PVK matrix is of the order of 100 nm. The spectral range of photoluminescence of such structures can be changed by varying the ratio of PVK to MEH-PPV. The current-voltage characteristics of composite light-emitting diodes based on PVK: MEH-PPV films indicate p -type conductivity. It has been shown that a decrease in the MEH-PPV nanoparticle concentration in the PVK matrix shifts the threshold values of the bias for the onset of electroluminescence toward smaller values and makes the photoluminescence and electroluminescence spectra more similar to the spectrum of the white light-emitting diode. The influence of the form of the polymer and polymer nanoparticles on the mechanisms of injection and transport of charge carriers and the radiative recombination in the studied structures has been discussed.

Description: The structural, X-ray diffraction, and electrophysical studies of hybrid superconducting hetero-structures with an interlayer of cuprate antiferromagnetic Ca 1 − x Sr x CuO 2 (CSCO) with the upper electrode Nb/Au and the lower electrode Y B a 2 Cu 3 O 7 − δ (YBCO) have been carried out. It has been experimentally shown that the epitaxial growth of two cuprates, YBCO and CSCO, results in the formation of an interface on which the enrichment of the CSCO interlayer with charge carriers proceeds to a depth of about 20 nm. In this case, the conduction of the enriched CSCO region proves to be closer to metallic, whereas the CSCO film deposited onto the NdGaO 3 substrate is a Mott insulator with hopping conduction.

Description: The temperature dependences of the inverse mobility of nondegenerate two-dimensional electrons in scattering by impurity ions in heterostructures with a narrow spacer have been investigated using the Al x Ga 1 − x As/GaAs heterostructure as an example. Correlations in the arrangement of impurity ions have been taken into account in the model of hard spheres on a plane. The influence of the form of the structure factor in the electron mobility has been considered.

Description: The slip of a single edge dislocation in an elastic field of point defects chaotically distributed over a crystal with allowance for a high hydrostatic pressure has been studied theoretically. The numerical estimations have demonstrated that hydrostatic compression of some metals and alloys increases the dislocation drag force by point defects in them by several tens of percent.

Description: The effect of cyanine dye additives on the photoelectric, nonlinear optical, and photorefractive properties of polyvinyl carbazole composites based on closed single-walled carbon nanotubes has been investigated. It has been found that these characteristics are affected by the dye in which the lowest unoccupied molecular orbital (LUMO) lies below the level of the photoexcited nanotube. The addition of this dye to the composite leads to a 14-fold increase in the quantum efficiency of the generation of mobile charge carriers under irradiation by a laser (1064 nm) in the absorption region of the nanotubes. Moreover, the addition of the dye to the composite decreases the third-order susceptibility χ (3) , presumably, due to the opposite orientations of dipoles of the dye and the nanotube upon adsorption of the dye on the nanotube. The addition of the dye to the composite also provides a twofold increase in the two-beam photorefractive amplification factor of the laser beam with a wavelength of 1064 nm. The obtained values of the two-beam photorefractive amplification factor reach 120 cm −1 .

Description: This paper presents the results of the investigation of c -Si/[Si/Mo] n /Si multilayer nanoperiodic structures by X-ray absorption near-edge structure (XANES) spectroscopy using synchrotron radiation. Changes in the fine structure of XANES Mo L 2,3 spectra confirm the formation of the silicide phase on heterophase interfaces Si/Mo/Si due to the solid-phase interactions between silicon and molybdenum layers.

Description: The potential inherent in integrated characterization of multilayer periodic systems employed in development of extreme-ultraviolet mirrors was demonstrated using the example of Mo/Si structures grown by magnetron sputtering in different technological regimes. An integrated study provided mutually consistent data on the thicknesses and crystal structure of the layers, as well as on the quality of the interfaces. Measurements by atomic force microscopy permitted a comparison of surface roughness of the substrates and the multilayer systems grown on them. An analysis of the power spectral density functions revealed that low-frequency roughness is replicated from the substrate, whereas the high-frequency one can become smoothed out in the course of growth. X-ray diffractometry performed in the thin film mode showed that the Mo layers in the samples studied have different crystal structures, from the amorphous and polycrystalline to the [110]-textured one. An analysis of the transmission electron microscopy data confirmed that there is a difference in the degrees of crystallinity of Mo layers. The thicknesses of individual layers, the period, and the irreproducibility of the thicknesses and the period were determined using X-ray reflectometry. The root-mean-square roughness amplitude of the interfaces was estimated, and the existence of transition layers originating primarily from the Si layer was demonstrated. The study was used to formulate a proper strategy for the analysis of multilayer periodic systems with nanosized layers.

Description: This paper presents the results of investigating the crystal structure of thin films of the Co 40 Fe 60 composition obtained by magnetron sputtering on their magnetic properties and properties of ferromagnetic nanostructures formed from these films using the optical and electron lithography. It has been found experimentally that magnetic properties of the structures depend on the crystalline-grain sizes, which can be controlled by means of deposition of additional buffer layers of various materials ∼1 nm thick on the substrate under the ferromagnetic film. It has been shown that the crystallite size can be the main factor that determines the minimal lateral sizes of the structures with specified magnetic properties, which are formed from thin ferromagnetic films.

Description: The hydrogen chemical adsorption on a single-walled carbon nanotube (6, 6) has been studied by quantum-chemical computer simulation. Different variants of hydrogen coverage of the nanotube have been considered, and the dependences of the adsorption energy and the nanotube strain energy on the coverage density have been found. In addition, the adsorption has been considered on both the outer and inner surfaces of the nanotube wall. It has been established that some adsorption conformations are unstable, which leads to fracture of the nanotubes.

Description: Experimental evidence for the possibility of controllably transforming the habit of copper microcrystals formed by electrodeposition has been presented. Selective evolution of microcrystal facets with a specific crystallographic orientation has been performed by a premeditated change in the chemical composition of a standard sulfuric electrolyte. The experiments have proved the existence of a small particle with icosidodecahedral morphology as an intermediate stage of the evolution of the small particle from an icosahedron to a dodecahedron and demonstrated some elastic-energy relaxation channels associated with inhibition of the growth of low-energy facets of electrolytic copper microcrystals.

Description: It has been shown that the variational principle can be used as the practical way to find the electron density and the total energy in terms of the density functional theory without solving the Kohn-Sham equations (the so-called orbital-free approach). The equilibrium interatomic distances and binding energies found using examples of diatomic systems Si 2 , Al 2 , and P 2 are in good agreement with the published data. The results obtained for Si-Al, Si-P, and Al-P dimers are also close to the results obtained by the Kohn-Sham method.

Description: The dependence of the magnetization reversal field of an elliptic submicrometer magnetic particle on the parameters of the material and sample configuration has been numerically studied. A method for calculating the magnetostatic field using the Fourier transform has been described in detail. The simulation results have demonstrated, in particular, that the normalized magnetization reversal field of a particle is independent of the exchange length at its rather large values.

Description: The electron paramagnetic resonance (EPR) spectra of Eu 2+ impurity centers in SrMoO 4 crystals have been studied in the temperature range of 1.8, 100–300 K. A hyperfine structure has been simulated for 151,153 Eu of different EPR transitions observed experimentally at different temperatures and external magnetic field orientations. A unique set of all parameters of the spin Hamiltonian for the known sign of the hyperfine interaction parameters A i has been determined. It has been found that the diagonal parameters | b n 0 | of the spin Hamiltonian decrease with increasing temperature; however, the parameter b 4 4 increases. The results of the study have demonstrated that | b 2 0 ( T )/ P 2 0 ( T )| ∼ const for 151,153 Eu in this single crystal.

Description: Two samples of detonation-synthesized ultradispersed diamond have been studied using X-ray diffractometry and small-angle X-ray scattering. It has been shown based on the X-ray diffractometry data that two samples contain regions with both the diamond and graphite-like lattices. Grain radii inside both samples are evaluated from the small-angle scattering data as 30–50 nm. The samples also contain low-dimensional components. A broad Bragg peak corresponding to a set of interplanar distances from 5 to 15 nm is revealed in the small-angle scattering curve of sample no. 1. A structural model of ultradispersed diamond particles, which represents the diamond core surrounded by concentric graphite shells similar to the onionskin, is confirmed.

Description: The elastic hysteresis and residual deflection of the aluminum D16 alloy samples corresponding to the model of a circular plate clamped along its perimeter have been studied at low (the beginning of the Hooke region) mechanical stresses. It has been shown that these characteristics depend substantially (change several times) on the sample state provided by different heat treatment conditions. The non-destructive method used in this work has a high accuracy and can be used to estimate the strength, yield stress, and fatigue life of metals.

Description: The transmission/reflection spectra of bilayer structures consisting of thin amorphous and polycrystalline Pb(Zr 0.52 Ti 0.48 )O 3 ferroelectric films deposited on dielectric substrates of magnesium oxide MgO and sapphire α-Al 2 O 3 were measured in the frequency range of 5–4000 cm −1 . Based on these spectra and using the dispersion analysis method, the spectra of complex dielectric permittivity ɛ*(ν) and dynamic conductivity σ′(ν) of the films were simulated, the electrodynamic parameters of the films were determined, and the dielectric dispersion responsible for the formation of static permittivity was found.

Description: The influence of the structure factors (sizes of grains and precipitates) on the dislocation structure formed in polycrystals and alloys behind the shock wave front (elastic precursor) has been theoretically discussed in terms of the dislocation kinetic relationships and kinetic equation for the dislocation density. The critical conditions of the transition from the cellular dislocation structure to a uniform dislocation distribution have been formulated. These conditions are used to determine the dependences of the critical pressure, above which the dislocation distribution becomes uniform, on the grain size and precipitate volume density.

Description: The crystal structure of solid solutions in the Bi 1 − x Pr x FeO 3 system near the structural transition between the rhombohedral and orthorhombic phases (0.125 ≤ x ≤ 0.15) has been studied. The structural phase transitions induced by changes in the concentration of praseodymium ions and in the temperature have been investigated using X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. It has been established that the sequence of phase transformations in the crystal structure of Bi 1 − x Pr x FeO 3 solid solutions with variations in the temperature differs significantly from the evolution of the crystal structure of the BiFeO 3 compounds with the substitution of other rare-earth elements for bismuth ions. The regions of the existence of the single-phase structural state and regions of the coexistence of the structural phases have been determined in the investigation of the crystal structure of the Bi 1 − x Pr x FeO 3 solid solutions. A three-phase structural state has been revealed for the solid solution with x = 0.125 at temperatures near 400°C. The specific features of the structural phase transitions of the compounds in the vicinity of the morphotropic phase boundary have been determined by analyzing the obtained results. It has been found that the solid solutions based on bismuth ferrite demonstrate a significant improvement in their physical properties.

Description: A general theory of the spectrum of normal waves propagating in magnetic structures with periodically modulated parameters has been developed. Based on the method of tensorial Green’s functions, spin-wave mode approach, and Floquet-Bloch theorem, a general form of the dispersion relation has been obtained for dipole-exchange spin waves propagating in a one-dimensional magnonic crystal formed by an arbitrary spatially periodic modulation of all magnetic and geometric parameters in the Maxwell’s equations and the Landau-Lifshitz equation. An original method has been proposed for taking into account an arbitrary profile of the modulation of the chosen parameters. The efficiency of the presented theory has been demonstrated using a simple example of the description of an experimental spectrum of a dynamic magnonic crystal.

Description: The effect of an external electric field on the electromechanical properties and regularities of the resistive switching of a vertically aligned carbon nanotube (VA CNT) has been studied experimentally using scanning tunneling microscopy. It has been shown that the VA CNT resistivity ratio in the high- and low-resistance states is higher than 25 as the distance between the scanning tunneling microscope (STM) probe and the VA CNT is 1 nm at a voltage of 8 V and depends on the voltage applied between the probe and the VA CNT. The proposed mechanism of resistive switching of VA CNTs is based on an instantaneous deformation and induction of a VA CNT internal electric field as a result of the sharp change in the time derivative of the external electric field strength. The obtained results can be used for the design and fabrication of resistive energy-efficient memory elements with a high density of storage cells on the basis of vertically aligned carbon nanotubes.

Description: A glass of the Li 2 O-11.5GeO 2 composition has been crystallized by heating and isothermal treatment near the devitrification temperature. The thermal properties and electrical conductivity σ of the glass in an alternating-current electric field have been investigated in the process of crystallization during the heating. The dependences σ( T ) have been measured for isothermally crystallized Li 2 O-11.5GeO 2 samples. Glass-ceramic samples in an intermediate metastable state with a high electrical conductivity have been synthesized by heat treatment of the initial glass. At T ∼ 500 K, the electrical conductivity of the intermediate state is one order of magnitude higher than that of the initial glass and three orders of magnitude higher than in the case of glass-ceramics consisting of Li 2 Ge 7 O 15 crystallites and the GeO 2 amorphous phase. It has been assumed that an increase in the electrical conductivity σ of the samples in the intermediate state is caused by the electrical conductivity of subsurface layers and is determined by the presence of a large number of nanometer-scale ordered regions in the structure.

Description: It has been shown that, in the GeSi/Si(001) heterosystem at lattice parameter mismatches of ∼2% and more, a small critical thickness of the introduction of dislocations leads to the implementation of the mechanism of induced nucleation of misfit dislocations. This mechanism consists in that the stress field of an already existing 60° dislocation provokes introduction of a secondary 60° dislocation with an opposite-sign screw component. As a result of the interaction of such dislocation pairs, edge misfit dislocations are formed, which do control the plastic relaxation process. This mechanism is most efficient when dislocations are introduced at the GeSi film thickness only slightly exceeding the critical thickness of the introduction of 60° dislocations, and there are threading dislocations. The dominant type of misfit dislocations (60° or edge) in the Ge-on-Si(001) system can be controlled by varying the mismatch parameter in the heteropair.