bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resonant Raman Scattering in ZnxHg1–xSe
Authors: Kumazaki K. 
Published: July 2007

AbstractRaman scattering by phonons is measured in narrow‐gap semiconductor, ZnxHg1–xSe, with x = 0 to 0.4 on (100) surface near the E1 + Δ1 energy gap at room temperature. Plasmon–LO phonon coupling modes are explained by a model taking into account the two‐mode behaviour of TO phonons. The photon energy dependence of scattering intensity shows a strong enhancement near the E1 + Δ1 energy gap. The results obtained from the experiments are compared with the results of Raman scattering, far‐infrared reflection, and ellipsometric measurements of other narrow‐gap semiconductors.
Triplet Molecular Excitations in Potassium Halide Cyanide Crystals. I. The CN– Impurity Centre
Authors: Camargo S. S. , von der Weid J. P. 
Published: July 2007

AbstractThe decay kinetics and emission intensity of the UV emission associated with the a3II → X1Σ+ electronic transition of the CN– molecular ion in potassium halides are investigated between 10 and 450 K. Two different energy transfer mechanisms from the host crystal to the impurity molecules are observed: the free exciton diffusion and the thermally activated migration of VK centers. A non‐radiative process is observed at high temperatures and is attributed to the coupling of the molecular excitation to local lattice phonons, probably the breathing mode of the neighbouring cations.
Free Energies of Polyatomic Polarizable Dipole‐Active Particles in Polar Media
Authors: Marsagishvili T. A. , Machavariani M. N. 
Published: July 2007

AbstractA calculation method is given of free energy change of polyatomic polarizable dipole‐active particles at their dissolution in inhomogeneous polar media. Two mechanisms of interaction between the particles and polar media are considered: solvatational and fluctuational mechanisms including ion–dipole and dipole–dipole interactions. Received analytical expressions permit to carry out the calculations for the dissoluted particles with any finite number of intramolecular degrees of freedom, taking into account the spatial and frequency dispersion of media.
Thermodynamics of Deformation under Irradiation
Authors: Sarce A. , Savino E. J. 
Published: July 2007

AbstractAn irreversible thermodynamic model is proposed for describing the deformation of a crystal under stress and irradiation. A thermodynamic inequality is found to relate the lattice straining and stress with the irreversible part of the free energy density. As an application of the model the case of straight dislocation climbing under irradiation is studied.
Crystal Dynamics of F.C.C. Inert Gas Solids
Authors: Mishra S. K. , Singh T. N. 
Published: July 2007

AbstractResults for the phonon dispersion curves along the [ζ00], [ζζ0], [ζζζ], symmetry directions and the Debye characteristic temperatures for Ne, Ar, Kr, and Xe rare gas solids are obtained on the basis of a five‐parameter non‐central force model. These results are compared with the experimental values with remarkable success. The Cauchy discrepancy is also explained on the basis of the model.
Phonon Dispersion in an α‐Perylene d12‐Crystal at 10 K
Authors: Schleifer J. , Kalus J. , Schmelzer U. , Eckold G. 
Published: July 2007

AbstractPhonon dispersion curves for the 24 external and some of the internal modes in α‐perylene‐d12 (C20D12) are measured at 10 K for the [ζ00], [0ζ0], and [00ζ] directions by coherent inelastic neutron scattering and Raman scattering. Calculations are performed with a semi‐rigid‐molecule‐model, based on well‐known 6‐exp‐potential functions. The agreement between measurements and calculations is satisfactory. Because of strong mode coupling the identification of the character of the closely neighbouring phonons is often not unique.
Theoretical Investigation of Ferroelastic Phase Transition of Pure and Mixed Alkali Cyanide Systems by the Elastic Dipole Model. II. The Cubic–Monoclinic Phase Transition of Pure Rubidium Cyanide
Authors: Yang Zhengju , Luty F. 
Published: July 2007

AbstractThe cubic–monoclinic structural phase transition of RbCN is investigated with the elastic dipole model. The calculation shows that the monoclinic structure of RbCN consists of two groups of dipoles of equal number but aligning in two different orientations, which are obtained from the strain of the unit cell in agreement with the experiments. A stable configuration of the two groups of dipoles is proposed. The alternate displacement of the cations calculated from this configuration agrees with the experiment in direction but is too large in magnitude due to the elastic continuum model used. The interaction between neighboring dipoles is the main part of the ordering energy in contrast to the ferroelastic case of KCN. In fact a new kind of ordering transition – antiferroelastic phase transition – is proposed for RbCN.
Nonlinear Optical Nutation on Interexciton Transitions in Cu2O. Analogue of the Equidistant Three‐Level System
Authors: Shmiglyuk M. I. , Bardetskii P. I. , Tiron S. D. 
Published: July 2007

AbstractThe nonlinear nutation on the optical transitions between the IS(Λ) and 2P(Λ, 2Λ, Λ, Λ) exciton states of the Cu2O yellow series is studied theoretically. An idealized case is considered when one coherent excitonic mode of a macroscopic amplitude is created in the 2P(Λ) state by the external resonant pumping. It is shown that in this case the CO2‐laser induced dipole transition scheme is the same as for the model equidistant three‐level system. The evolution of the nonstationary state of the exciton–photon system to the stationary one due to the polarization damping is considered. The phase diagrams are investigated both, at strong and weak damping.
A Weak‐Coupling Calculation of the Binding Energy and Effective Mass of a Polaron in a Multiple Quantum Well
Authors: Lai W. , Butcher P. N. 
Published: July 2007

AbstractThe Fröhlich electron–phonon interaction in a multiple quantum well structure (MQW) is studied in a perturbation scheme. The dispersion relation of the polaron is obtained with an analytic form factor in a well and an overlap factor between wells. The polaronic binding energy and effective mass are compared with results for a single quantum well.
On the Theory of Auger Recombination in Disordered Semiconductors. A Green's Function Approach
Authors: Quang Doan Nhat 
Published: July 2007

AbstractA Green's function approach based on the density‐operator formalism is developed to calculate the lifetime of Auger recombination in disordered semiconductors, taking explicitly into account translation‐symmetry breaking and the contribution of band‐tail states. The theory is applied to disordered materials which can be described by the smooth random field model. It is shown that the classical approximation is sufficient to produce the effect of the disorder on Auger recombination processes. Then a general expression for the Auger lifetime is derived in the form of the volume and configuration average of a local lifetime. The influence of the random field is reduced to a modification of the energy conserving δ‐function and the distribution functions of non‐equilibrium carriers. The Auger lifetime or recombination rate depends on the mean square of the random potential fluctuation, Ψ1. In the case of nondegenerate semiconductors, the Auger recombination rate is exponentially enhanced with increasing Ψ1, so that an estimate of the random parameter might be possible from Auger lifetime measurements. As an example, the Auger coefficient for p‐type GaSb is evaluated for the case of the random field due to thermal fluctuations of charge carrier concentrations.
The Hyperfine Field Distribution in Thin Films of Binary Diluted Alloys
Authors: Urbaniak‐Kucharczyk A. 
Published: July 2007

AbstractIn amorphous ferromagnets spatially fluctuating exchange interaction give rise to a critical behaviour substantially different from crystalline magnets. Within the framework of a molecular field theoretical approach, a non‐local Landau‐Ginzburg equation is applied for thin amorphous film in the vicinity of phase transition point by means of a correlated molecular field, which can only vary on larger scale than the spin correlation length. Therefore, the manner how the structural disorder affects the critical behaviour changes with temperature. The calculation of the hyperfine field distribution measured in the Mössbauer experiment is done for the case of a binary alloy with simple cubic lattice. Numerical results for various surface parameters and temperatures are obtained.
Correlation between the Mössbauer and Semiconductor Parameters of Tin Telluride
Authors: Motiejūnas S. , Baltrūnas D. , Gečiauskaitė N. , Makariūnas K. 
Published: July 2007

AbstractThe observed correlation between the 119Sn Mössbauer isomer shift δ and the hole concentration in tin telluride is explained on the basis of the latest literature data on the peculiarities of the peculiarities of the band structure. It is evaluated that the temperature change from 40 to 400 K should not influence the isomer shift.
Kondo Effect and Direct Interaction. Renormalization‐Group Approach
Authors: Allub R. 
Published: July 2007

AbstractWilson's renormalization‐group approach is used to study the magnetic susceptibility of a model with two different magnetic impurities. The particular case is considered in which only one impurity is coupled to the conduction band (Kondo coupling) and there is a direct interaction (JL) between the two impurities. For ferromagnetic interaction (JL > 0) between the localized impurities, a magnetic ground state is found and a divergent susceptibility at low temperatures. For (JL < 0), two different Kondo temperatures and a nonmagnetic ground state are distinguished.
The Irreversibility and Viscosity Effects in Dilute Ferrimagnets
Authors: Efimova N. N. , Popkov Yu. A. , Tkachenko N. V. 
Published: July 2007

AbstractAn investigation is made of magnetic viscosity and irreversibility in systems with short‐range superexchange (dilute ferrimagnetic oxides), where these effects are directly to the nature of the spin glass (SG) state. It is found that the irreversibility effects may be attended by other characteristic features of the SG state (the magnetic viscosity, the dependence of the low temperature behaviour of σZFC (T) on the field H), or alternatively, may exist without them, and are proper to various magnetic states: SG, superparamagnetic, as well as non‐collinear and disordered ferrimagnetic ones. In contrast, the existence of the logarithmic‐low magnetic viscosity is uniquely associated with the SG state.
Surface Spin‐Wave Mode Excitation in Bulk Amorphous FeNiB Alloys
Authors: Frait Z. , Fraitová D. 
Published: July 2007

AbstractExperimental data on the surface spin‐wave mode excitation and magnetic surface anisotropy energy obtained by the method of ferromagnetic resonance and antiresonance are presented for as‐prepared and annealed bulk samples of amorphous alloys FexNi1−xB0.2, x = 0.4 to 0.7. For x = 0.4 the temperature interval 200 to 650 K is investigated, for x = 0.5 to 0.7 RT‐results are introduced.
Reflectivity Spectra and Band Structure of the Zinc and Cadmium Diphosphides
Authors: Sobolev V. V. , Kozlov A. I. , Polygalov Yu. I. , Tupitsyn V. E. , Poplavnoi A. S. 
Published: July 2007

AbstractPrecision reflectivity spectra of the tetragonal ZnP2, CdP2 for E ∥ c, E ⟂ c and monoclinic ZnP2 for E ∥ a, E ∥ b, E ∥ c are investigated at 80 and 293 K. New reflectivity structures are observed including the exciton peaks in the monoclinnic ZnP2. The thermoreflectivity spectra of CdP2 are obtained at 193 K. The band structure of the tetragonal ZnP2 and CdP2 and CdP2 is calculated using the pseudopotential method at the symmetrical points T, Z, A, M, R. A comparison of the reflectivity data with the results of the ZnP2 band structure is made.
Crystal Structure and Magnetooptical Properties of Cd1−xMnxTe with High Mn Concentrations
Authors: Babonas G. , Galazka R. R. , Pukinskas G. , Šileika A. 
Published: July 2007

AbstractCd1−xMnxTe crystals with compositions 0.1 < x < 0.7 are studied. It is observed that in Mnconcentrated crystals (x = 0.40, 0.64) are structural peculiarities which cause extra reflections in the Laue and Debye‐Sherrer patterns and the optical anisotropy of those samples. In Cd1−xMnxTe samples with x = 0.64 the effective birefringence is 4.2 × 10−3 and the splitting of the exciton peak is equal 0.7 meV. The dispersion of the Faraday rotation at 300 K is well described by a single‐oscillator approximation for all the investigated Cd1−xMnxTe crystals. In the region of the absorption edge of highly Mn‐concentrated crystals the magnetic circular dichrosism specta have additional contribution which can be related with an excitation of Mn2+ ions. In these crystals the temperature dependennce of magnetic circular dichroism in reflectance shows some peculiarities which are interpreted by the influence of antiferromagnetic interaction between the Mn2+ spins.
Local Static and Dynamic Atomic Displacements in Disordered Niobium Carbide
Authors: Gusev A. I. , Rempel A. A. 
Published: July 2007

AbstractA neutron diffraction study is made of disordered niobium carbide NbCy (1.00 ≧ y ≧ 0.75) in the region of its homogeneity. The dependences of the mean‐square static and dynamic displacements of atoms on the composition of niobium carbide are determined. It is suggested that in niobium carbide localized metal—carbon bonds predominate over delocalized metallic interactions.
A Study of the Second and Third Neighbour Structure in Chalcopyrite CuGaSe2 by EXAFS
Authors: Antonioli G. , Lottici P. P. , Razzetti C. 
Published: July 2007

AbstractEXAFS measurements on CuGaSe2 at the Ga, Cu, and Se K‐absorption edges are performed and the second and third shells of atoms around the absorbing one are considered. It is shown that an investigation up to the third neighbours by standard EXAFS data analysis techniques, in the usual approximations, gives reliable results in this complex structure. The EXAFS spectra can then give useful information on the structural distortions in the tetragonal chalcopyrite compounds.
A Study of Interstitial Impurity Diffusion by the Linear Response Theory
Authors: Kogutyuk I. P. , Keivan P. N. , Rarenko I. M. 
Published: July 2007

AbstractThe diffusion of interstitial impurities is studied within the linear response theory using Hamiltonian describing localized and quasi‐free states of impurity particles, as well as their interaction with lattice vibrations. The diffusion coefficient for light impurity atoms is shown to deviate from the Arrhenius‐type linear dependence ln D ∼ 1/T at high temperatures.
Lattice Dynamics of the Force Constant Disordered Crystal Pd0.90Ru0.10
Authors: Maliszewski E. , Sosnowski J. , Bednarski S. 
Published: July 2007

AbstractPhonon dispersion relations for Pd0.90Ru0.10 single crystal at room temperature are measured along the directions [100], [110], and [111] by inelastic neutron scattering. The Born‐von Karman analysis, using the seven‐neighbour model, is carried out, and the force constants and elastic constants are calculated. The phonon frequency shifts, Δω(q), and the self‐energy functions, ∑j(q, ωj(q)), for all the branches are determined from the experimental phonon data for Pd0.90Ru0.10 and Pd. The self‐energy shows a rich and coherent structure and reveals unique information relevant to a theoretical model of a phonon induced fast diffusion in certain metals. The same structure of the self‐energy is observed in the sample after annealing at 1420°C.
Phonon Assignments in II–VI and III–V Semiconductor Compounds Having Zincblende‐Type Structure
Authors: Ram R. K. , Kushwaha S. S. , Shukla A. 
Published: July 2007

AbstractThe lattice infrared absorption and/or Raman spectrum peaks for ZnSe, InP, and GaSb semiconductor compounds having zincblende‐type structure are assigned to calculated critical point phonon frequencies at Γ, X, L, and W critical points. The assignments are consistent with Birman's selection rule and support lattice dynamical results. The reliability of the calculated critical point phonons for these compounds is checked by Brout's sum rule and compressibility and also comparing them with neutron or Raman data.
Comparative Analysis of Tendencies in the Temperature‐Induced Changes in Electronic Structure of Iron and Nickel
Authors: Sandratskii L. M. , Guletskii P. G. 
Published: July 2007

AbstractA previously proposed symmetrized method for the calculation of the electronic structure of spiral magnetic configurations is employed in the study of non‐collinear magnetic configurations of iron and nickel. It is shown that there is a marked difference of the tendencies of changes in the electronic structure of both metals being studied due to the increase of the angle between the spins of neighbouring atoms. A qualitative interpretation of the observed changes is given in terms of a simple two‐band model. It is also shown that the difference in the behaviour of the electronic structure of both, iron and nickel leads to a substantially different behaviour of a self‐consistent local magnetic moment and total electronic energy as a function of the angle between the spins of the neighbouring atoms.
Shallow Donor Binding Energies in Semiconductors in a Magnetic Field
Authors: Sukumar B. , Navaneethakrishnan K. 
Published: July 2007

AbstractThe binding energies of the P donor in Si and the Si and S donors in GaP at the cation and anion sites, respectively, in strong magnetic fields are calculated using a variational procedure. The central cell effects are taken into account using an Yukawa type potential and its effects on the ionization energies are obtained for various magnetic fields. In GaP the electron—lattice coupling (polaronic effect) is also taken into account both, in fixing the parameters of the model potential and also in the computation of binding energies. It is shown that the central cell effects are important especially for magnetic fields of the order of γ ≈︁ 100. The contribution from the electron—lattice coupling is small and seen to decrease with the increase of magnetic field in confirmation with previous works. The central cell effect enhances the electron—lattice coupling appreciably, the enhancement being 30 to 100% for the range of magnetic fields investigated.
Photostimulated Acoustoelectronic Effects in Semiconductors in the Long Wavelength Region
Authors: Anh Vo Hong , Shon Nguyen Hong 
Published: July 2007

AbstractThe interaction of the photoelectrons with the sound waves in the long wavelength region in semiconductors is considered using the classical continuum model for the lattice motion together with the kinetic equation in the relaxation time approximation describing the electron subsystem. Currents and fields arising in the sample are calculated. An de electric field due to the deviation of the electron distribution function from the equilibrium exponential form under the action of a light wave (and in the presence of a magnetic field) is revealed that is absent in the short wavelength limit. The possibility of an experimental observation of this effect is discussed.
Josephson Properties of a Homogeneous Superconducting Film
Authors: Ilinikh A. I. , Shapiro B. Ya. 
Published: July 2007

AbstractA theory of localized superconducting states arising in a thin superconducting film deposited on the surface of a ferromagnetic particle is constructed. It is shown that a periodic superconducting structure is formed in such a film. The critical magnetic field, temperature, and Josephson current are determined.
Quantum 1/f Noise Associated with Intervalley Scattering in Nondegenerate Semiconductors. I. Analytical Calculations
Authors: Kousik G. S. , van Vliet C. M. , Bosman G. , Luo Horng‐Jye 
Published: July 2007

AbstractScattering of charged particles is accompanied by the emission of soft photons. Quantum theory of 1/f noise, based on the infrared quasi‐divergent coupling of the system to the electromagnetic field, indicates that the current associated with a beam of scattered charged particles exhibits 1/f noise. Based on this quantum theory the previously obtained results are extended for mobility fluctuations to include mobility fluctuations due to intervalley f‐ and g‐type processes. The fluctuations in the scattering rates are derived, and these are related to the mobility fluctuations through the relaxation time solutions of the Boltzmann transport equation. Hooge's law for 1/f noise is derived and explicit expressions are obtained for the mobility fluctuations due to intervalley scattering. This is then applied to n‐type silicon to arrive at the overall Hooge parameter, αH, as a function of temperature. It is found that the intervalley scattering processes do contribute little to the mobility, but are quite significant for the noise. The contribution to the noise is significant because of the large changes in the electron wavevector associated with intervalley scattering processes. Excellent agreement with well known experimental results is observed for the mobility as well as the Hooge‐parameter.
Thermodynamics of Localized Magnetic Singlets and 1/2‐Spins in the Plane
Authors: Hudák O. 
Published: July 2007

AbstractClassical thermodynamics is found of localized magnetic singlets and 1/2‐spins in the plane using the monomer‐dimer approximation. Static magnetic susceptibility behaviour observed in the La2CuO4 paramagnetic phase is qualitatively explained within the theory.
Ground State of Ising Ferromagnet with Biquadratic Exchange of Negative Sign. The Case of Large Spin S = 5/2
Authors: Iwashita T. , Uryǔ N. 
Published: July 2007

AbstractFor spin−5/2 Ising ferromagnet with bilinear and biquadratic exchange interactions J and J′, the magnetization is calculated using the pair model approximation. The temperature dependence of the magnetization shows an anomalous behaviour at J′ = −J/10 suggesting an instability of the ferromagnetic ground state. On the other hand, the ground state spin structure is determined from the J′‐dependence of the energy of a single spin in various spin structures. The results show an occurrence of the phase transition at J′ = ‐J/10, agreeing well with the one obtained from the anomalous behaviour of the magnetization. Furthermore, the phase transitions have also been pointed out to occur at J′ = ‐J/6, J′ = ‐J/3, and J′ = ‐J.
Dynamics of Exciton Reflection Spectra on the Change of the Incidence Angle in NaI Crystals
Authors: O'Connel‐Bronin A. A. , Treshchalov A. B. 
Published: July 2007

AbstractOver about sixty‐year investigations of the intrinsic absorption edge of NaI its absorption (reflection) spectra have been worked out in detail, but they have a „static”︁ character, which is one of the reasons that made their interpretation difficult. In the present work, reflection spectra at oblique incidence, including a nearly sliding one are experimentally investigated, which allows to trace their dynamics and to analyse their peculiarities from a new point of view. Thanks to that the energy of the longitudinal exciton and respectively that of the longitudinal‐transverse splitting are estimated. The structure of the high‐energy side of the n = 1 exciton line first observed by Van Sciver is analysed.
The Influence of the Vibrational Entropy on the Specific Heat of the Order—Disorder Transition in Alloys
Authors: Tuijn C. , Bakker H. 
Published: July 2007

AbstractThe influence is outlined of vibrational entropy on the specific heat curve of a simple cubic AB crystal, assuming nearest‐neighbour interaction. The calculation of the energy is carried out by means of a Monte Carlo method using the Ising model. For the vibrational entropy an exact analytical expression is applied. The shift in the critical temperature and the sharpening of the peak in the specific heat curve are quite considerable. A change in the vibrational entropy of 0.5k per atom is possible.