The strong topology on the algebra of polynomials

It is shown that under a quite general condition on the operator T (unbounded, symmetric) and on the domain $\text{D}$ for the representation x → T of the algebra $\text{P}$(x) on $\text{D}$ in $\text{P}$(T) the strongest locally convex topology τ_∞ coincides with the strong topology σ^$\text{D}$.     

Spin-Wave Resonance in Ge : Mn Thin Films with Percolation Magnetic Ordering

The mechanism of excitation and propagation of spin waves in Ge: Mn thin films with different nominal manganese concentrations (2, 4, and 8 at % Mn) with percolation magnetic ordering is explored. Concentration dependencies of Curie temperature T_C(n) and spin wave rigidity D(n) are determined, which enables to find the index of correlation distance. An exotic percolation magnetic state of samples of Ge: Mn thin films is confirmed by rectifying experimental dependences D(n) and D/T_C(n) in coordinates accepted in the percolation theory.     

Electron-phonon interactions and temperature dependence of infrared absorption in the conducting organic salt trimethylbenzimidazol-tetracyanoquinodimethane (TMB-TCNQ)

Infrared spectra of the simple salt TCNQ with trimethylbenzimidazol were studied vs temperature. The analysis of the mechanisms causing the absorption coefficient of the salt TMB-TCNQ to be dependent on temperature shows that three elements should be taken into account. The changes in electronic interactions described by the function W(T), the reduction of occupation of the ground state described by the function n_g(T), and the changes in geometry of the dimer described by the function D(T) are the main mechanisms defining the thermal dependences of the absorption coefficients. The electron-phonon coupling constants for different temperatures were determined.     

Magnetic properties of amorphous Co75W25

Saturation magnetization M(T), spin wave stiffness D and Curie temperature T_c of amorphous Co₇₅W₂₅ were determined by magnetic measurements. Tungsten reduces these quantities more than metalloids or 3d-transition metals do. T_c is below room temperature. The ratio D/T_c, however, is equal to that observed on a fcc single crystal of Co₉₂Fe₈ and on amorphous Co-Ti alloys.     

Superconductivity and electronic specific heat in V-Mo system

The parameters of superconductivity and specific heat are determined from the low temperature specific heat measurements of V_(1−x)Mo_x (0 ⩽ x ⩽ 1) solid solutions. The coefficient of electronic specific heat γ decreases with increasing Mo concentration and shows a minimum around 80 at. %Mo. Debye temperature θ_D varies slightly over the whole composition range. The superconducting transition temperature T_c also decreases with increasing Mo concentration. The variation of T_c is explained by the variation of γ and discussed in terms of the band structure.     

On phonon localization in nearly one-dimensional solids

The condition for experimental observation of effects of phonon localization in nearly one-dimensional dielectric solids are investigated. While there seems to be no observable effect in thin wires, phonon localization can lead to a minimum in the thermal diffusivity curve D_T(T) of solids with a chain-like structure and weak inter-chain molecular forces.     

A monte-carlo/molecular dynamics study of the diffusional recombination kinetics of C(a) + O(a) → CO(g) on Pt(111)

The diffusion constants for C and O adsorbates on Pt(111) surfaces have been calculated with Monte-Carlo/Molecular Dynamics techniques. The diffusion constants are determined to be D_C(T)=(3.4 × 10^?3e^{$\text{?13156}\text{T}$})cm²s^?1 for carbon and D_O(T) = (1.5×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1 for oxygen. Using a recently developed diffusion model for surface recombination kinetics an approximate upper bound to the recombination rate constant of C and O on Pt(111) to produce CO_(g) is found to be (9.4×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1.     

Connections between thermodynamic quantities and vacancy and diffusion characteristics in binary metallic solid solutions

With the use of the similarity of interatomic potentials relations concerning vacancy and diffusion characteristics in disordered regular solid solutions have been derived. It has been shown that the vacancy concentration is constant along ifT_c(x) = T_A + (T_B ? T_A)x + 2ΔT_x(1?x), (T_A and T_B are the melting points of pure components A and B respectively, and ΔT is proportional to the excess enthalpy of mixing, x is the concentration of the atoms B) which is proportional to the binding energy of the crystal. The validity conditions of several empirical rules known in the literature are also analyzed. It has been found that the generalization of the well-known rule for self- and impurity diffusion in pure metals has the following form In $\text{D}{}_0{}^{\mathrm{z}}\text{(x) ～ p}\text{Q}{}^{\mathrm{z}}\text{(x)}\text{T}{}_{\mathrm{c}}\text{(x)}$ (Z = AorB) where p is a constant for alloys having identical structures (D₀^z(x) and Q^z(x) denote the preexponential factors and the activation energies respectively). The results calculated from the relations derived were compared with experimental data for tracer diffusion in the systems AgAu, CuNi (having slight deviation from regularity), Pb-Tl (showing ordering phenomena) and AlZn (clustering effects) and a good agreement was found.     

Colormagnetic confinement in the quark–gluon thermodynamics

Nonperturbative effects in the quark–gluon thermodynamics are studied in the framework of vacuum correlator method. It is shown, that for T > T ₀ = 175 MeV two correlators: colorelectric D ₁ ^E (x) and colormagnetic D ^H (x), provide the Polyakov line and the colormagnetic confinement in the spatial planes respectively. As a result, both effects produce the realistic behavior of p(T) and I(T), being in good agreement with numerical lattice data.     

Disordering effects and property changes in fast neutron irradiated YIG

Damage region structure and property changes of YIG irradiated atD=10¹⁸?7.8×10¹⁹ n/cm² were studied. Damage regions at 300 K were found to consist of 1) a core of Fe³⁺ paramagnetic phase (PP) withgΔ=0.8 mm/s; 2) a shell of Fe³⁺ intermediate magnetic phase with heavily distorted bond geometry and <H _eff>≤300 kOe; 3) Fe³⁺ (a, d) surrounded by oxygen vacancies and interstitials. The dose dependence of PP concentration is given byC _PP=1-exp(?βD), yielding PP core radiusr _PP=12,5 Å. Magnetic ordering in PP was found to arise atT _tr=90 K. NGR probabilityf′ under irradiation was found to decrease linearly according to Δf′/f′=?C _PP(D). Net magnetization change was found, using the Gilleo model, to obey an analogous relationship ΔM(T)/M(T)=?C _PP(D).T _c dose dependence is given by ΔT _c/T _c=?0.5×C _PP(D) and can be related to lattice parameter change to yield Δa ₀/a ₀=(1.42±0.04)×10^?4×C _PP(D). External field experiments revealed a complex dependence ofK ₁ on PP concentration, elastic stress field magnitude and a with a minimum atD=10¹⁹ n/cm².     

Calculation of the diffusion coefficient in acoustic turbulence

The first (Born) approximation commonly used to calculate the diffusion coefficient D_T of a passive scalar in acoustic turbulence is shown to be insufficient. Even for a small main parameter—the Mach number, M?1—the next approximation gives a larger contribution to D_T than does the first approximation, but negative in sign. We present a procedure for correctly calculating D_T based on the solution of a nonlinear DIA (direct interaction approximation) equation for the mean Green’s function of the problem. We include an additional term in the general formula for D_T that directly describes the compressibility of acoustic turbulence. This term has not been known previously and has been disregarded even in the Born approximation. A positive value was obtained for D_T=CM³u₀/p₀. The spectrum E(x) was assumed to be smooth at distances Δ x～M²?1.     

Kondo behaviour of the solid solution (Ce1−xLax)PtGa

The solid solution (Ce_1−xLa_x)PtGa has been studied through X-ray diffraction, magnetization (σ(B)), magnetic susceptibility (χ(T)), electrical resistivity (ρ(T)), magnetoresistivity (MR) and heat capacity (C_P(T)) measurements. The Néel temperature (T_N=3.3 K) for CePtGa is lowered upon La substitution as observed from χ(T) and ρ(T) measurements. The Kondo temperature T_K as calculated from MR measurements is comparable to T_N and also decreases with La substitution. The volume dependence of T_K is in accordance with the compressible Kondo lattice model and a Doniach diagram of the results is presented. C_P(T) measurements are presented for CePtGa, Ce_0.2La_0.8PtGa and LaPtGa and the results are discussed in terms of the electronic and magnetic properties. Other features of interest are anomalies in ρ(T) and C_P(T) due to crystalline electric field effects and metamagnetism as observed in σ(B) studies for samples with 0≤x≤ 0.3.     

Optical and theoretical investigations of V ions in CdZnTe crystal

High-resistivity CdZnTe:V crystals are investigated by photoluminescence (PL) and by time-resolved PL in the infrared spectral range. A double peaked emission band is detected around 0.8 eV and it is related to vanadium doping. No-phonon lines of the internal transitions were detected. This emission is interpreted as a balance between the ⁴T₁(⁴P)→⁴T₁(⁴F) internal transition and an electronic transition from the conduction band to the ⁴T₁(⁴F) ground state of V²⁺. The corresponding decay time after laser excitation gives evidence to the contribution of two different recombination processes. These two emission bands are separated by time-resolved luminescence. Crystal-field calculations of the detected transition energies based on Tanabe-Sugano scheme are presented and the Racah parameter B and crystal-field intensity D_q were determined.In addition, a model is developed in terms of one-electron orbital, to explain the characteristics of the PL excitation processes of V²⁺. Excitations with above and below band edge energy confirm the proposed schemes.     

Static and dynamic properties of supercooled thin polymer films

The dynamic and static properties of a supercooled (non-entangled) polymer melt are investigated via molecular-dynamics (MD) simulations. The system is confined between two completely smooth and purely repulsive walls. The wall-to-wall separation (film thickness), D, is varied from about 3 to about 14 times the bulk radius of gyration. Despite the geometric confinement, the supercooled films exhibit many qualitative features which were also observed in the bulk and could be analyzed in terms of mode-coupling theory (MCT). Examples are the two-step relaxation of the incoherent intermediate scattering function, the time-temperature superposition property of the late time α-process and the space-time factorization of the scattering function on the intermediate time scale of the MCT β-process. An analysis of the temperature dependence of the α-relaxation time suggests that the critical temperature, T _c, of MCT decreases with D. If the confinement is not too strong ( D≥10monomer diameter), the static structure factor of the film coincides with that of the bulk when compared for the same distance, T - T _c(D), to the critical temperature. This suggests that T - T _c(D) is an important temperature scale of our model both in the bulk and in the films. Received 12 September 2001     

Classification of <Emphasis Type="Italic">T</Emphasis>-odd asymmetries for prescission and evaporated light particles in ternary and quaternary nuclear fission induced by cold polarized neutrons

A unified mechanism of the emergence of T-odd ROT- and TRI-asymmetries is proposed for describing experimental T-odd asymmetry coefficients D(θ) in the angular distributions of prescission alphaparticles that are emitted in true ternary and quaternary nuclear fission reactions induced by cold polarized neutrons. The mechanism is related to the different ways in which the Coriolis interaction of the total spin of a polarized compound fissile nucleus with the orbital moment of alpha-particles affects even (for ROT-asymmetries) and odd (for TRI-asymmetries) components of the amplitude of an undisturbed angular distribution of emitted alpha-particles. Coefficients D_ROT(θ) and D_TRI(θ) derived with this mechanism for T-odd ROT- and TRI-asymmetries successfully describe the dependences of corresponding experimental coefficients for ²³⁵U and ²³⁹Pu nuclei over the range of angles θ, and for the ²³³U nucleus in the angular range of 60° < θ < 110°. It is explained why only ROT-type T-odd asymmetries emerge for evaporated neutrons and γ-quanta emitted by fission fragments in similar reactions if we allows for the Coriolis interaction of the total spin of the compound fissile nucleus with the orbital moments of the fission fragments and the wriggling vibrations of the above nucleus near its scission point.     

Elastic and thermal properties of Zr z Nb1 − z C x N y solid solutions

The temperature and concentration dependences of the elastic moduli and the thermal linear expansion coefficient of Zr _z Nb_{1 ? z} C _x N _y solid solutions containing from 3 to 8 at % of structural vacancies in a nonmetallic sublattice have been found. The temperature dependences of the Debye temperature Θ_D(T) have been calculated using the elastic data and the data on the heat capacity. It has been shown, using carbide NbC_0.97 as an example, that the Θ_D(T) dependences found from the elastic properties and the heat capacity coincide in the temperature range ～220–300 K. By analogy with the niobium carbide, the heat capacity C _p (300) of Zr _z Nb_{1 ? z} C _x N _y solid solutions of various compositions is calculated based on the values of Θ_D(300) determined from the elastic properties.     

Gaussian free field in the background of correlated random clusters,formed by metallic nanoparticles

The effect of metallic nano-particles (MNPs) on the electrostatic potential of a disordered 2D dielectric media is considered. The disorder in the media is assumed to be white-noise Coulomb impurities with normal distribution. To realize the correlations between the MNPs we have used the Ising model with an artificial temperature T that controls the number of MNPs as well as their correlations. In the T → 0 limit, one retrieves the Gaussian free field (GFF), and in the finite temperature the problem is equivalent to a GFF in iso-potential islands. The problem is argued to be equivalent to a scale-invariant random surface with some critical exponents which vary with T and correspondingly are correlation-dependent. Two type of observables have been considered: local and global quantities. We have observed that the MNPs soften the random potential and reduce its statistical fluctuations. This softening is observed in the local as well as the geometrical quantities. The correlation function of the electrostatic and its total variance are observed to be logarithmic just like the GFF, i.e. the roughness exponent remains zero for all temperatures, whereas the proportionality constants scale with T ? T _c . The fractal dimension of iso-potential lines (D _f ), the exponent of the distribution function of the gyration radius (τ _r ), and the loop lengths (τ _l ), and also the exponent of the loop Green function x _l change in terms of T ? T _c in a power-law fashion, with some critical exponents reported in the text. Importantly we have observed that D _f (T) ? D _f (T _c ) ~ 1/√ξ(T), in which ξ(T) is the spin correlation length in the Ising model.     

Size and interface effects on Curie temperature of perovskite ferroelectric nanosolids

A simple and unified model, without any adjustable parameter, is established for size effect on Curie temperature of low-dimensional ferroelectrics (thin films, nanowires and nanoparticles), T _c(D), where D denotes size of low-dimensional ferroelectrics. T _c(D) function is based on consideration on the size dependence of spontaneous polarization of low-dimensional ferroelectrics P _s(D), which is determined by the misfit strain at the ferroelectrics/substrate interface. It is shown that P _s(D) and T _c(D) functions decrease or increase when the misfit strain is tensile or compressive. The numerically predicted results are in agreement with the available experimental results of BaTiO₃ and PbTiO₃ nanoparticles and thin films.     

Phonon properties of vanadium-substituted lanthanum niobate derived from heat-capacity measurements

We have measured the 3–400 K heat capacity of vanadium-substituted lanthanum niobate LaNb_1−x,V_xO₄ (0 < x⩽0.35) to determine how the relevant averaged properties, or moments, of the phonon spectrum 〈ωⁿ〉 relate to certain other lattice properties of these compounds, most noteworthy of which is a large decrease in the paraelastic-ferroelastic transformation temperature T_c with x. The pertinent moments, represented by their corresponding Debye temperatures, are θ_D(−3) corresponding to the lowest frequency modes; θ_D(0) associated with the geometric mean frequency of the entire spectrum; and θ_D (2) identified with the high-frequency modes that are sampled at the upper end of the temperature range. We find that θ_D(−3) falls rapidly with x and this effect can be correlated with the comparably sharp drop in T_c. There is little effect of composition on θ_D(0) and θ_D (2) because the phonons that govern soft-mode behavior represent only a small fraction of the mode population. In the vicinity of T_c the temperature dependences of the free energies of the tetragonal and monoclinic phases are so similar that the discontinuity in C_p is immeasurably small.