bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasmon‐Mediated Pairing Arrangement of the One‐Dimensional Electron System
Authors: Yanetka I. 
Published: July 2007

AbstractThe possibility of various types of pairing arrangements is examined in a one‐dimensional system in which the effective interparticle interaction of Coulomb type is evaluated in the plasmon‐pole approximation. The insulating state arising from the particle‐hole pairing arrangement appears to dominate strongly over the superconductive effects. The dependence of the transition temperature on the band width is calculated for a set of typical parameter values with the help of the derived integral equation which formally coincides with the well‐known equation of the theory of superconductivity.
Finite Temperature Valence Transition in Mixed Valence Systems
Authors: Ghosh N. K. , Sarkar R. L. 
Published: July 2007

AbstractThe valence transition at finite temperature in mixed valence (MV) systems is investigated using the extended Falicov‐Kimball (F‐K) model with Coulomb f–f and the electron‐phonon (EP) interactions. The role of different interactions and the influence of temperature on the valence transition are studied. It is found that the lowering of temperature favours the transition. The results are compared with existing experimental findings.
Relativistic Impacts on Electrical Resistance of a One‐Dimensional Finite Crystal
Authors: Roy C. L. , Basu Chandan 
Published: July 2007

AbstractA relativistic study of electrical resistance in a one‐dimensional finite crystal with rectangular barrier type of atomic potentials is reported. The procedure applied is based on an appropriate relativistic generalisation of Landauer's non‐relativistic treatment of electrical resistance for a finite number of potential barriers. The relativistic impact on electrical resistance in our model is studied only in regard to the velocity of electrons. The quantitative extent of such an impact is critically discussed.
Calculation of Electrical Resistivity of Liquid Transition Metals
Authors: Ononiwu J. S. 
Published: July 2007

AbstractThe transport properties of liquid transition metals are discussed on the basis of Ziman's theory as generalized by Evans, Greenwood, and Lloyd. The effect of d‐band resonance in transition metals is simulated in the nearly‐free electron approximation where the ordinary (V‐matrix) pseudopotential form factor is replaced by the T‐matrix form factor in the transport integral. The T‐matrix form factor is derived in a closed form from the transition‐metal model potential V‐matrix form factor by solving the appropriate T‐matrix integral equation. The solution takes into account the deviation of the electron density of states at the Fermi level from the free‐electron value, through the ratio g = N(EF)/N0(EF), which is estimated from experimental heat capacity and McMillian's electron phonon renormalization constant in group‐B transition metals to have a mean value of order g = 2 for liquied transition metals. Based on this estimate of g and Mott's form of Ziman's formula, the electrical resistivity is calculated for all group‐B liquid transition metals using the parameters of the transition‐metal model potential obtained by Animalu in 1973. The results are in reasonable agreement with the experiment.
Magnon‐Induced O‐Hole Interaction in a pdtJ Model for CuO2 Superconductors
Authors: Bryja L. , Kolley E. , Kolley W. 
Published: July 2007

AbstractAn effective model for O‐hole quasiparticles is derived from the t˜pp–Jpd–Jdd–Jpp (or pdtJ) model stemming from the minimal version of the Emery model. The underlying procedure involves an antiferromagnetic (AF) Holstein‐Primakoff transformation, a Schrieffer‐Wolff transformation, and an AF Bogolyubov transformation. The investigation of the diagonal part of the effective vertex shows the dominance of the AF magnon‐mediated repulsion over the a priori attraction between O‐hole quasiparticles along the boundaries of the magnetic Brillouin zone. In view of the pairing, formal similarities to the spin‐bag mechanism are pointed out.
Specific Features of the Defect Formation in LiF Crystals as a Result of Implantation of Li+ and F+ Ions
Authors: Alekseeva L. I. , Titov Yu. M. , Urusovskaya A. A. , Knab G. G. , Guseva M. I. , Gordeeva G. V. 
Published: July 2007

AbstractThe results of an investigation of the mechanical, electrical, and optical properties in the near‐surface layer of LiF crystals irradiated with Li+ and F+ ions (energy 80 keV, fluence up to 1017 cm−2) are presented. The hardening in the layer, the thickness of which is by an order of magnitude larger than the ion penetration depth, as well as a significant difference in conductivity change are revealed. The conductivity change is explained in the case of F+ implantation by a combination of cation vacancies with hole centers and in the case of Li+ implantation by the appearance of an electron component in conductivity with an activation energy of 0.36 eV. By optical measurements the temperature change of the position and half‐width of the colloidal absorption band is observed. The latter one is connected with electron‐phonon interaction in Li colloidal particles. It is found also that the colloidal band can be separated into three elemental bands, the shape of which is nearly Gaussian in wavelength coordinates due to the statistical particle‐size distribution.
Impact Parameter Dependence of the Electronic Stopping Power for Channeled Ions
Authors: Nakagawa S. T. 
Published: July 2007

AbstractIn order to examine the dependence of the electronic stopping power (dE/dx) on the impact parameter p, the energy dissipation of axially channeled ions with curved trajectories is studied theoretically by means of a cluster model. dE/dx is accounted in the framework of nonlinear molecular dynamics (MD) coupled with the local density approach (LDA) based on the Lindhard‐Winther (LW) theory. A correction factor of 2 is introduced to compensate the lower dE/dx, especially for low‐energy ions. B ions are implanted into Si 〈100〉 and 〈110〉 at incident energy in the region 10 keV ≦ E0 ≦ 10 MeV. Results are the following. Firstly two kinds of solid‐state effects on the p‐dependence of dE/dx are found at high and low E0, respectively. At high E0 (> 100 keV) the core electrons reveal quite different profiles of dE/dx versus p than valence ones, and at low E0 (< 100 keV) the topological difference in the electron distribution among axial channels appears in those profiles, which cannot be explained by means of collisions with single atom. Secondly, the p‐dependence of dE/dx is intended to adapt the simple form dE(p)/dx = A exp (‐sp/a). The factor s due to core electrons increases distinctly with E0, while that due to valence electrons is almost invariant, smaller than 0.3.
Transport Properties in Liquid Metal Binary Alloys
Authors: Jain K. C. , Gupta N. , Saxena N. S. 
Published: July 2007

AbstractA theoretical study of the transport properties viz., the shear and bulk viscosity, thermal conductivity, and surface tension in some liquid metal binary alloys at different concentrations is presented. The results obtained for these transport properties in liquid NaK, NaCs, KCs, KPb, NaPb, NaSn metal alloys employing the model given by Davis et al. are in a good agreement with the results calculated using other theoretical approaches.
Phonon Properties of a Three‐Component Fibonacci Chain
Authors: Hu A. , Yang F. , Jiang S. S. 
Published: July 2007

AbstractThrough the transfer matrix method the phonon properties of a three‐component Fibonacci chain are studied. The eigenfrequencies and the eigenstates are computed using a finite quasi‐periodic chain and periodic boundary conditions. Computed results show that not only the scaling index of the phonon spectrum, but also the eigenstates depend on the frequency ω.
Deformation Potentials in AIIBIVC2V Ternary Chalcopyrite Semiconductors
Authors: Rincón C. , Fernández B. J. 
Published: July 2007

AbstractDeformation potentials of valence and conduction bands in AIIBIVC2V chalcopyrite semiconductors are calculated from the variation of the energy gap with temperature and pressure. From a comparison with their binary analogues AIIIBV it is found that values of deformation potentials in these compounds are considerably higher than in the binaries which could explain their lower carrier mobility.
Phase Diagram of a Quantum Transverse Spin‐1 Ising Model with Random Fields
Authors: Ma Y. Q. , Ma Y. G. , Gong C. D. 
Published: July 2007

AbstractThe quantum spin‐1 Ising system with random fields is investigated by combining the pair approximation with the discretized path‐integral representation. An analytical expression for the second‐order phase transition is derived for all symmetrical probability distributions of random fields, and phase diagrams for Gaussian and bimodal random fields are obtained numerically.
Stability and Thermodynamical Properties of Liquid NaSn Alloys
Authors: Michael Helen M. , Sahay B. B. 
Published: July 2007

AbstractStability and the alloying behaviour of liquid NaSn alloys are investigated with the presumption that a chemical complex of the form Na4Sn or Na3Sn exists in liquid NaSn alloys and this is used to determine their free energy of mixing and also entropy of mixing. The computed values of the free energy of mixing and entropy of mixing as a function of concentration are in good agreement with the experimental results. It can, therfore, be inferred that the thermodynamical behaviour of liquid NaSn alloys may be explained, even with the presumption of only one type of chemical complex instead of two as assumed by Tamaki et al. and Hoshino [1, 2].
Effect of the Short‐Range Order in Binary Alloys
Authors: Jezierski A. 
Published: July 2007

AbstractThe influence of the chemical short‐range order effect on the electronic density of states in binary alloys is studied. The electronic structure is calculated by the TB LMTO CPA method. Increasing density of states at the Fermi level N(EF) is observed with increasing short‐range order parameter in Pt0.75Mn0.25 and Hf0.25Rh0.75 alloys.
Anomalous Hall Effect in Cerium Based Kondo Systems
Authors: Prabhu R. B. , Barbosa A. F. 
Published: July 2007

AbstractA self‐consistent perburbation theory to calculate magnetoresistivity, susceptibility, and the Hall constant for the crystal field split cerium based systems is employed. In this theory, excitonic and other correlations are included self‐consistently. The resulting non‐linear integral equations for the conduction electron scattering amplitude are solved perturbatively retaining terms up to fourth order in V, the Anderson mixing interaction. We calculate the Hall constant as a function of temperature for various positions of the f‐level. We compare our results with the experimental data on cerium based compounds.
Transmission and Conversion Electron Mössbauer Investigation of Fe81B13.5Si3.5C2 Glass under RF Thermal Treatment
Authors: Bibicu I. , Rogalski M. S. , Nicolescu G. 
Published: July 2007

AbstractPulsed 54.8 MHz rf annealing of Fe81B13.5Si3.5C2 glass induces – before any crystallization can be detected by X‐ray diffraction – different short‐range ordering effects reflected in the simultaneous recording of conversion electron (CEM) and transmission (TM) Mössbauer spectra. A quadrupole interaction analysis reveals an almost identical threshold energy for the bulk stress relief and for the chemical short‐range order growth evidenced in CEM spectra, attributed to different strength and distribution of the atomic bonding.
Characterization of the Crystal Quality of Calcites by Electron Paramagnetic Resonance
Authors: Vassilikou‐Dova A. B. 
Published: July 2007

AbstractThe linewidths Bpp and anisotropies in the electron paramagnetic resonance spectra of Mn2+ impurities are measured in calcite single crystals and used for the determination of the origin of line broadening. Two different mechanisms of broadening, structural and chemical, are distinguished. From the differing angular dependences of the observed linewidths, large differences in the crystal quality are inferred. The differences in quality are also apparent in the EPR spectra of powder calcites, but no information about the mechanisms can be obtained.
L2 and L3 X‐Ray Absorption Edge in Fluoride Glasses
Authors: Wang Wen‐Cai , Chen Yu , Hu Tian‐Dou 
Published: July 2007

AbstractThe Ba and Nd L2,3 X‐ray absorption spectra in ZrF4BaF2NdF3 and some ZrF4BaF2 binary glasses are studied. It is observed that the intensities of the white lines (WLs) in Nd and/or Ba L2,3 edges from these materials differ from those of their fluorides. Besides, the intensity ratios of the WLs in Ba and Nd L2,3 edges, L3/L2 deviate from the statistical value. These ratios for the studied glasses are also not the same as those from the corresponding fluorides. However, these changes of both the WL intensities and the ratios L3/L2 in Ba L2,3 edges differ from those in Nd L2,3 edges. These differences are discussed and attributed to the differing interaction between Ba or Nd and F in the glasses.
Phonon Frequencies in Metallic Glasses
Authors: Agarwal P. C. , Kachhava C. M. 
Published: July 2007

AbstractThe Ashcroft empty core model potential is used to derive the effective interatomic potential, Veff(r), and the pair correlation function, g(r), of metallic glasses through the pseudopotential approach. The only parameter rc (core radius) is chosen to make the calculated g(r) as close as possible with available experimental data. Veff(r) alongwith g(r) of the glass is used to evaluate longitudinal and transverse phonon frequencies by the use of the Takeno and Goda equations. The formulation reproduces the main characteristics of the dispersion curves obtained by computer simulation techniques.
On a Simplified Analysis of the Effective Electron Mass in Ultrathin Films of Nonparabolic Semiconductors in the Presence of a Parallel Magnetic Field
Authors: Ghatak K. P. , Bhattacharyya D. 
Published: July 2007

AbstractAn attempt is made to study the effective electron mass at the Fermi level in ultrathin films of nonparabolic semiconductors in the presence of a parallel magnetic field on the basis of a newly derived electron dispersion law. It is found, taking n‐Hg1−xCdxTe and In1−xGaxAsxP1−y lattice matched to InP as examples, that the effective Fermi level mass depends on the subband index in addition to the Fermi energy due to the presence of the magnetic field. The effective masses corresponding to different subbands increase with increasing surface electron concentration and decreasing film thickness. Besides, thc numerical values of the masses in quaternary alloys are smaller than those for ternary semiconductors. In addition, the corresponding well‐known results of ultrathin films of nonparabolic Semiconductors in the absence of the magnetic field are also obtained as special cases of our generalized formulation under certain limiting conditions.
The Temperature Dependence of the Energy Gap in Cd0.22, Hg0.78Te. II. Hall Effect Measurements
Authors: Hlídek P. , Grill R. , Höschl P. , Moravec P. , Zvára M. 
Published: July 2007

AbstractHall effect data evaluated with various assumptions regarding the energy band parameters are compared with the results of optical measurements. The energy gap Eg, of an ideal crystal described by the Kane band model should be distinguished from the energy difference ET between conduction and valence band tail states which contribute also to the carrier transport. The temperature coefficient of Eg(T) is proposed to be higher than that used in the well‐known Hansen‐Schmit‐Casselman relation, while ET, versus temperature varies more slowly as a consequence of a broadening of the band tails with increasing temperature.
Magnetic Field Induced Triplet Exciton Polariton in CuCl
Authors: Ando T. , Hasuo M. , Nagasawa N. 
Published: July 2007

AbstractThe integrated optical absorption I (B) due to the Z3‐triplet exciton in CuCl is measured at 4.2 K as a function of an external magnetic field B (O ≦ B ≦ 0.2 T) in Voigt configuration. I (B) shows the characteristic B‐dependence whose behaviour is ranging between quadratic and linear on B. It is found that this B‐dependence of I is caused by the correlation between the B‐dependent singlet‐triplet mixing and the sample‐dependent damping of the Z3‐triplet exciton. The effects of spatial dispersion due to the finite effective mass of the triplet exciton are taken into account assuming Pekar's ABC. The conceptional transition from a classical Lorentz model to the polariton model is demonstrated experimentally. An application to the characterization of the sample is also discussed.
Correlation between X‐Ray Chemical Shift and Partial Charge in Some Cobalt Systems
Authors: Mehta C. P. , Chetal A. R. 
Published: July 2007

AbstractThe chemical shift of the X‐ray K‐absorption edge of cobalt in the systems CoSO4. 2H2O, CoCl2. 6H2O, Co2O3, Co3O4, CoO, CoS, and (NH4)2SO4 · CoSO4 · 6H2O is studied using a 40 cm Cauchois type bent crystal spectrograph of transmission type. On the basis of least‐square regression analysis a cubic relationship between the X‐ray chemical shift and the partial charge on the absorbing ion is suggested. The relation is utilized for estimating the partial charge on the Co ion in the system (NH4)2SO4 · CoSO4 · 6H2O.
Phonon Disperision Curves of Diamond and Silicon within the Quasi‐Ion Model
Authors: Mohaupt M. , Falter C. , Klenner M. , Ludwig W. 
Published: July 2007

AbstractThe phonon dispersion curves for diamond and silicon in the quasi‐ion model are calculated and additionally the effect of anisotropic breathing is studied. Within the rigid quasi‐ion model (RIM) the influence on the phonon dispersion of the localization of the expansion set (Gaussians) for the quasi‐ions is discussed. Furthermore the phonon dispersion curves are investigated taking anisotropic breathing into account. Such an extension allows to influence special modes in the spectrum, in particular the LA‐mode at the L point which is poorly represented in the RIM. Also calculated are phonon‐induced changes of the electronic density in this model for some modes. Anisotropic breathing is associated with a quadrupole contribution to the displacement‐induced change in density in contrast to the RIM where the quadrupole moment vanishes for symmetry reasons.
Optical Absorption, Fluorescence, and Thermally Stimulated Emission on CaF2 : Dy: Pb Single Crystals
Authors: Sastry S. B. S. , Kennedy S. M. Moses 
Published: July 2007

AbstractThe optical absorption (OA) spectra of unirradiated crystals of CaF2 doped with 0.1% Dy (by mol%) and 0.1% Pb, hereafter called crystal I, and doped with 0.2% Dy and 0.1% Pb, called crystal II, indicate the presence of a small amount of dysprosium in their divalent state (Dy2+). There is an increasing absorption towards 6.5 eV. On y‐irradiation the concentration of Dy2+ ions is found to increase. Fluorescence of these crystals shows characteristic Dy3+ emission at 1.62, 1.85, 2.16, and 2.85 eV (4F9/2→6H9/2), 6H11/2, 6H13/2, 6H15/2. In thermoluminescence (TL) glow after γ‐irradiation at room temperature crystal I shows six peaks in the temperature range (300 to 700 K) studied. Dy3+ is found to be the major luminescent centre under all these glow peaks. In addition to the Dy3+ emission bands there are two bands in the UV region at 4.94 and 5.93 eV in TL emission. For higher concentrations of lead the results are somewhat different. Crystal III (with 0.01% Dy and 0.5% Pb) and crystal IV (with 0.02% Dy and 0.5% Pb) show a strong absorption band around 6.4 eV. On irradiation prominent absorption bands are observed around 2.04 and 3.21 eV. These are attributed to an F centre associated with the rare‐earth ion in its divalent state (Dy2+ –F centre complex), akin to the FA centre in alkali halides. It is also found that the lead ions (Pb2+) when excited, transfer their energy to nearby Dy3+ ions, leading to the characteristic emission of Dy3+ ions.
Study of Diffusion on a Deterministic Fractal
Authors: Dasgupta R. , Ballabh T. K. , Tarafdar S. 
Published: July 2007

AbstractFractal systems exhibit anomalous diffusion where the mean square distance covered in a random walk (RW) is related to time t as 〈r2〉 ∼ t2/dw with dw ≠ 2. The presence of a bias along any direction in fractal systems gives rise to competing effects ‐ enhanced diffusion as well as trapping at dead ends. A random walk on a Vicsek fractal (VF) is studied. The same exponent dw is obtained from a similar vibrating mass‐spring system. Introducing a bias along the positive Y‐direction in RWs, the competing effects are also observed. Results are compared with another well‐studied deterministic fractal, the Sierpinski gasket (SG).
Investigation of Ballistic Phonon Propagation in Quartz by the Time‐of‐Flight Method
Authors: Sujak‐Cyrul B. , Szczepański J. , Tyc T. 
Published: July 2007

AbstractThe ballistic phonon propagation in α‐quartz is measured in directions z and y, for different bolometer currents, by the time‐of‐flight method. For higher currents on time‐dependent bolometer signal curves more singularities are observed than it was reported earlier. On the basis of calculations the observed singularities are explained as separately detected phonon modes and the increase of their number is connected with a diminution of the bolometer active area by increase of bolometer current for very thin aluminium bolometers.
Superconducting Properties of Y1−xCaxSrBaCu2.9Ga0.1O6+z
Authors: Suryanarayanan R. , Ouhammou L. , Leelaprute S. , Le Nagard N. 
Published: July 2007

AbstractThe lattice parameters and ac susceptibility of Y1−xCaxSrBaCu2.9Ga0.1O6+z (x = 0, 0.05, 0.1, and 0.2) are reported. Tc decreases as a result of (0.1) Ga substitution from 83 to 67.5 K but increases to 79.5 and 80 K for x = 0.1 and 0.2, respectively. The present data in comparison with those on Al and Co which have been shown to occupy chain sites suggest strongly that Ga also preferentially occupies the chain sites.
On the Quasistochastic Behavior of Nonlinear Magnetization Oscillations in Orthorhombic Ferromagnets Induced by a Magnetic Pulse Field
Authors: Galkina E. G. , Stankiewicz A. , Maziewski A. 
Published: July 2007

AbstractIt is shown that large oscillations of magnetization (induced by fast changes of external magnetic field) in ferromagnets, of orthorhombic symmetry can show quasistochastic features: a slight deviation in initial state essentially changes the magnetization behavior for t → ∞. In contrast to the simplest uniaxial anisotropy case (where the quasistochastic behavior should be expected only after switching the in‐plane field on), the presence of orthorhombic anisotropy creates the new possibility of quasistochastic excitation after switching the external field off. This anisotropy component may also considerably change the ranges of quasistochastic behavior.
Static Multipole Polarizabilities and Shielding Factors for the S‐Electron Moving in the Screened Coulomb Potential
Authors: Kassim H. A. 
Published: July 2007

AbstractThe variational perturbation approach of Rivail and Rinaldi as generalized by Shukla and Easa is utilized to derive a 2L‐pole static polarizability and a shielding factor for the electron in the ground state moving in a screened Coulomb potential of Debye form. The final formulas are reduced to power series of the screening parameter D in the asymptotic region. The special cases discussed by Fowler can readily be obtained from the present generalized form by direct substitution of the corresponding L values.