bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiphoton interband absorption of light in semiconductors in external parallel electric and magnetic fields
Authors: Katana P. K. 
Published: July 2007

AbstractThe coefficient of the multiphoton interband absorption of light (MPA) in semiconductors in the presence of constant external, parallel electric and quantizing magnetic fields is calculated. It is shown that the MPA coefficient has an oscillatory character and the peaks correspond to the optical transitions on Landau levels. The following particular cases are considered: multiphoton electroabsorption (MPEA) and multiphoton magnetoabsorption (MPMA).
Monte‐carlo studies of energy straggling of electrons in solids. II. Consideration of electron angular scattering
Authors: Kotera M. , Murata K. , Nagami K. 
Published: July 2007

AbstractAn angular scattering effect of electrons in solids is taken into account in the previous Monte‐Carlo simulation model which has employed the modified Blunck and Leisegang (MBL) energy straggling distribution. The Mott cross‐section of elastic scattering is adopted for angular scattering. The electron trajectory consists of two kinds of steps; one is an elastic scattering mean free path as used in the conventional single scattering model, and the other is a step length defined using the MBL distribution in the previous paper. This simulation is applied to calculate several physical quantities such as backscattering and transmission coefficients, energy deposition etc. The calculated results are verified by comparing with the experimental data.
Electronic structure of neutral and charged point defects. A charge self‐consistent empirical tight‐binding study
Authors: Strehlow R. , Kühn W. , Hanke M. 
Published: July 2007

AbstractA charge self‐consistent description of the electronic structure of neutral and charged point defects in the framework of ETBM is presented. As in the case of recently performed charge self‐consistent TB parametrizations of pure crystals the approach is based on the consideration of both, intra‐and inter‐atomic electron‐electron interaction resulting in a functional dependence of TB eigen‐energies on the orbital population. Using the Koster‐Slater scattering‐theoretical method the theory is explicitly worked out for a five‐atom cluster containing the point defect and its four nearest neighbours. As a first application antisite defects in III–V compound semiconductors are treated. Results are discussed for both, neutral and charged defects.
Semiphenomenological theory of the Gd3+ S‐state splitting in low‐symmetry crystals
Authors: Levin L. I. 
Published: July 2007

AbstractA semiphenomenological theory for Gd3+ ground state splitting in low‐symmetry crystals is proposed. It allows to explain this splitting with an explicit indication of the Gd3+ excited states taken into account and to extract the characteristic parameters of the splitting which are independent of the angular and radial coordinates of the ligands.
EPE and spin‐flip Raman scattering in the n‐type magnetically mixed semiconductors
Authors: Ryabchenko S. M. , Semenov Yu. G. 
Published: July 2007

AbstractEffects on the EPR and spin‐flip Raman scattering (SFRS) of large‐radius electron centers (donors) are considered for magnetically mixed semiconductors. The effects are caused by the mixing of the spin states of electrons and the localized spin momenta (LSM) of magnetic ions through the carrier‐ion exchange interaction. The shape of the SFRS and EPR spectra in the “Zeeman region” is calculated as well as the dependence of the relative component intensity on the matrix element ratio of SFRS (EPR) transitions for the donor electron and LSM. The effects of the “disappearance” of the donor EPR in the course of the magnetic doping of semiconductors and the effect of the manifestation of LSM EPR in the magnetic resonance optically detected from the donor‐acceptor luminescence are explained. A superscattering effect is predicted for the collective spin of the LSM ensemble effectively interacting with the donor electron.
Orbit‐lattice interaction and mössbauer quadrupole splitting of Fe(II) in (NMe4)2FeCl4
Authors: Srivastava K. K. P. , Choudhary S. N. 
Published: July 2007

AbstractThe observed quadrupole splitting of 57Fe2+ in (NMe4)2FeCl4 shows a linear decrease with temperature over 87 to 237.5 K, which cannot be explained on the basis of the electronic states of Fe2+ in a static crystal field. The effect of orbit–lattice interaction is considered which produces a temperature dependent mixing between the dz2 and dx2–y2 electronic states with the emission and absorption of phonons of varying energies. The various lattice dynamical parameters are estimated and then quadrupole splitting is explicitely calculated as a function of temperature. One obtains a reasonably good agreement with the experimental data which shows that the vibrating lattice model is quite realistic and important.
Mössbauer emission studies of 57Co‐doped ZnO, Cu2O, and TiCoO3
Authors: Roset J. , Fernández A. , Obradors X. , Tejada J. 
Published: July 2007

Abstract57Co‐doped Mössbauer oxide sources are prepared at different temperatures and oxidation pressures. The appearance of the 57Fe3+ anomalous charge state is related with the p‐character of semiconductor oxide. Increasing the acceptor concentration increases the anomalous ferric line intensity in the Mössbauer spectra. The two location sites of 57Co in the ZnO matrix correspond to substitutional and grain boundary sites, respectively. The n‐character of ZnO oxide makes possible the appearance of the ferrous state in the corresponding Mössbauer spectra.
Asymmetry of the EPR absorption line in CdF2 with Y
Authors: Wilamowski Z. , Oczkiewicz B. , Kacman P. , Blinowski J. 
Published: July 2007

AbstractAn EPR absorption in CdF2:Y is investigated as a function of temperature. The shape of the observed derivative absorption line, which is symmetric at low T, becomes asymmetric at higher. The theoretical model of the line‐asymmetrydependence on the sample dimensions and conductivity shows a non‐monotonic behaviour of the line asymmetry ratio A/B in theregion where the skin depth is comparable to the sample thickness, in agreement with the experimental data.
Boundary conditions at multichannel specular reflection of the conduction electrons on the surface
Authors: Ustinov V. V. , Khusainov D. Z. 
Published: July 2007

AbstractA rigorous derivation of the boundary conditions for the quasiclassical distribution functiondescribing the multichannel reflection of the conduction electrons from the perfect surface of the ideal crystal is made by considering the equation of motion of the one‐electron density matrix. A generalization of the results obtained is given for the case of incoherent scattering of the charge carriers by the nonideal surface.
Effect of non‐locality in the calculation on liquid metal resistivity of transition metals
Authors: Oli B. A. , Ononiwu J. S. 
Published: July 2007

AbstractThe influence of non‐locality of pseudopotentials on liquid metal resistivity of transition metals is investigated. A simple first order approximation is used to evaluate this influence of non‐locality and calculations are carried out for a few transition metals. The agreement obtained between theory and experiment is good showing that local approximations are not adequate for the calculation of liquid metal resistivity of non‐simple metals.
The electrical properties of rapidly quenched CuNi alloys
Authors: Rossiter P. L. , Mair R. H. 
Published: July 2007

AbstractA series of CuNi alloys containing 10, 20, and 30 at% were rapidly quenched by melt spinning. This results in an unusual atomic and magnetic structure which is sensitive to the thermal and magnetic history of a specimen. An explanation of the changes in electrical resistance and magnetic susceptibility which result from a variety of heat and thermo‐magnetic treatments is given in terms of Ni clusters possibly associated with sub‐surface segregation effects and spin enhancement of the surrounding matrix.
Improvement of debye‐hückel evaluation of free carrier screening effects in semiconductors
Authors: Farvacque J. L. 
Published: July 2007

AbstractMost of the applications of the “energy loss” method for free carrier mobility calculations are based on Debye‐Hückel approximation for the evaluation of the free carrier screening properties. However, it is well known that, indeed, this approximation is fully available in a relatively high temperature range. The aim of this paper is to estimate, from Lindhard's dielectric function and in the effective mass approach some corrective terms which allow us to improve this approximation and consequently to extend the range of applicability of mobility calculations by the “energy loss” method.
Temperature and thickness dependence of electrical and thermal transport coefficients of Bi1–xSbx films in an anisotropic, non‐degenerate two‐band model
Authors: Völklein F. , Kessler E. 
Published: July 2007

AbstractThe thickness and temperature dependences of electrical and thermal transport coefficients (e.g. electrical conductivity, thermoelectric power, thermal conductivity) of Bi1–xSbx films are described by a non‐degenerated two‐band model, considering the anisotropic elliptical band structure (many‐valley model) of bulk Bi1–xSbx. The transport coefficients are measured in the temperature range 80 to 400 K on films with thicknesses 20 to 400 nm and the results are interpreted and discussed using the deduced relations.
AC transport in short n+nn+ layers
Authors: Sinkkonen J. , Eränen S. 
Published: July 2007

AbstractThe admittance of n+nn+ semiconductor structures is studied by solving self‐consistently the Poisson equation, the continuity equation, and the linearized Boltzmann equation in the relaxation time approximation for a spatially inhomogeneous electron system. Exact numerical results and an approximate, analytical solution are presented. In addition to the normal bulk admittance and the geometric capacitance of the central n region, the equivalent circuit of the structure consists of contact contributions, the magnitude of which depends on the length of the n region L. At low frequencies the effect of the contacts is to induce a conductance Gc, and a capacitance Cc, in parallel with Gc, in the equivalent circuit. On the other hand, above the plasma frequency of the n region the contact admittance vanishes because of the shunting of the capacitive elements.
Experimental study of the influence of lattice vibrations on the suppression effect at room temperature
Authors: Smirnov G. V. , Shvydko Yu. V. , van Bürck U. , Mössbauer R. L. 
Published: July 2007

AbstractThe anomalous transmission of resonant γ‐radiation through a perfect single crystal of 57FeBO3 is studied in the nearly pure nuclear Bragg reflection (330) at room temperature. The direct calibrations of the residual resonance absorption by means of reference absorber and the comparison of the obtained Mössbauer reflection spectra with computer calculations yield the result, that the anomalous transmission of resonant γ‐radiation does not follow the temperature law valid for the anomalous transmission of X‐rays. Evidence is obtained, that lattice vibrations at room temperature do not affect the suppression effect or do this at least much less than they affect the related Borrmann effect.
On the grain boundary segregation of sp‐valence impurities in B.C.C. transition metal
Authors: Masuda‐Jindo K. 
Published: July 2007

AbstractGrain boundary segregation of sp‐valence impurities in b.c.c. transition metals (α‐Fe) is investigated using a tight‐binding (TB) type electronic theory of s, p, and d‐basis orbitals: Particular attention is paid for Mg, Al, Si, P, S, and Cl impurities at a ∑ = 5 tilt grain boundary in α;‐Fe. Band parameters for host and impurity atoms are determined within Harrison's universal TB scheme and relative electronic energy levels are taken from atomic structure calculations by Herman and Skillman. It is shown that the segregation energy ΔEsegr for sp‐valence impurities is negative (attractive interaction) and exhibits parabolic trend as a function of the number of electrons Nimp (= Nimps+ +Nimpp) in the sp‐band.
Green function theory of a semi‐infinite ising ferromagnet in a transverse field
Authors: Shiwai B. A. , Cottam M. G. 
Published: July 2007

AbstractA Green function equation‐of‐motion method is employed to calculate the dynamic properties of a semi‐infinite spin system (or pseudo‐spin system) described by the Ising model in a transverse field. The excitations of the system are shown to be the bulk and surface spin waves, and the Green functions are employed to evaluate their spectral intensities and integrated power factors at temperatures above the transition temperature Tc. Some numerical examples are also included.
Multiple scattering approach to the XANES theory of alkali halide crystals. III. Comparison with the experimental X‐ray spectra
Authors: Gegusin I. I. , Datsyuk V. N. , Novakovich A. A. , Bugaev L. A. , Vedrinskii R. V. 
Published: July 2007

AbstractThe XANES K‐spectra of six alkali halide crystals (LiF, NaF, KF, LiCl, NaCl, KCl) are calculated in the framework of multiple scattering (Green function) cluster approach. The core hole and other potential effects are studied. The 57‐atom cluster predictions that employ the suitable crystalline potential accounting for the core hole effects as it follows from the “atomic relaxation” model, provide satisfactory agreement with the experimental spectra. Generally the core hole influence reveals as the nondramatic redistribution of the oscillator strengths along the spectrum although the striking changes occur in the Li K‐spectra.
The analytical deconvolution technique for the green function recursion expansion
Authors: Gläser U. H. , Rennert P. , Mašek J. , Velický B. 
Published: July 2007

AbstractThe analytical properties of Green functions in the complex energy plane are utilized in an approximative continuation of the Green function from the line Im z = ε towards the real axis. This procedure acts as an effective but incomplete deconvolution for the spectral density. As a result, a well‐resolved but smooth spectrum is obtained even in case where it is exactly represented by a set of delta functions. This property is employed in solving the termination problem of the recursion method, and the applicability of the whole proposed calculational scheme is demonstrated on the LCAO calculation of the electronic density of states in the ordered intermetallic compound TiTc.
Parametrization of electric‐dipole intensities in fN systems due to electron‐correlation effects
Authors: Kaminskii A. A. , Kornienko A. A. , Chertanov M. I. 
Published: July 2007

AbstractThe consideration of transfer processes of an electron from ligand to the trivalent lanthanide ion allows to obtain theeffective dipole‐moment operator containing the terms having complicated tensor structure. Using the second quantization technique as well as the canonical‐transformation method permit to write the expression for the electric‐dipole (4f‐4f)‐transition probabilities in a form, which is convenient for the interpretation of the experimental data. The expression for the transition probabilities contains traditional Ω2, Ω4, and Ω6 parameters as well as four additional D2, D4, L2, and L4 ones being due to the complicated tensorial structure of the electric‐dipole moment operator. The microscopic analysis carried out for the Er3+ ion in LaF3, single crystal shows that one can neglect the terms with L2, and L4 parameters. Using the new parametrization scheme containing five parameters (Ω2, Ω4, Ω6, D2, and D4,) the intensity spectroscopic properties of Pr3+ ions in Bi4Ge3O12, single crystal are non‐contradictorily described, where the hypersensitive inter‐manifold 3II4 → 3F2 transition is taken into account. On the basis of this parametrization scheme the best description of the experimental data as a whole as well as of the hypersensitive inter‐manifold 4I15/12 → 2H11/2, 4G11/2 transitions of Er3+ ions in Y3Al5O12, Lu3AI5O12, and BaYb2F8 single crystals are also obtained.
Localization in a one‐dimensional random potential with spatial correlation
Authors: Kasner M. , Weller W. 
Published: July 2007

AbstractThe role of oscillating vertices usually neglected in the Berezinskii diagram technique is analyzed in connection with a random potential, whose spatial correlation is generated by a Markov chain. It appears that the consideration of some of the oscillating vertices is necessary so that the theory can remark the spatial correlation. Correlation mainly leads to an increase of the localization length in comparison with an uncorrelated potential. However, there is a region of the parameter, where the localization length decreases. The Berezinskii diagram technique is used in a modified form.
Metal‐insulator transition and metastable state in high‐purity n‐InSb under high hydrostatic pressure
Authors: Kraak W. , Sschaller U. , Herrmann R. 
Published: July 2007

AbstractThe effect of hydrostatic compression (up to 1.2 × 103 MPa) on the galvanomagnetic properties of pure n‐InSb crystals is investigated. For samples with different excess donor concentrations n = ND – NA ⪅ 1014 cm−3 at T = 4.2 K a pressure‐induced metal–insulator transition is found at a critical pressure p = pc. Furthermore, besides the M‐I transition at high pressures (p > pc) and low temperatures pressure‐induced metastable properties are observed. The experimental data are explained using a model of a particular defect state which is resonant with the conduction band when not occupied (at low pressures p < pc), but which relaxes deep into the gap after capture of an electron (p > pc). From the analysis of the time dependences of the electrical properties the value of the potential barrier EB between the neutral and the ionized configuration of the impurity atom is determined. A rapid decrease of the potential barrier EB for pressures p > pc is found.
A reduced angular momentum expansion in the multiple‐scattering theory
Authors: Fritzsche V. , Rennert P. 
Published: July 2007

AbstractIn order to improve the calculations of ARPES, ARAES, and EXAFS a new approximation in the multiple‐scattering theory for the excited electrons is introduced, which is called reduced angular momentum expansion (RAME). In the RAME the incoming waves are approximated in the range of the scattering potential by a limited set of spherical waves with low angular momenta. This is a much better description than the plane wave approximation in the often used small scattering‐centre approximation. The RAME possesses a high accuracy for energies down to 40 eV and needs a substantially lower numerical effort than the full angular momentum expansion. For higher energies it can be further simplified and it modified small‐scattering‐centre approximation is obtained, which takes into account the curvature of the waves by means of effective scattering amplitudes.
Raman scattering from polaritons and plasmaritons in 6H‐SiC
Authors: Azhnyuk Yu. M. , Artamonov V. V. , Ya. Valakh M. , Litvinchuk A. P. 
Published: July 2007

AbstractThe results of Raman scattering studies of polariton and plasmon‐polariton (plasmariton) excitations in 6H‐SiC are presented. Polariton anisotropy and resonant coupling with one‐ and two‐phonon host lattice vibrations are discussed. The effect of free charge carriers upon the dispersion of polaritons in nitrogen‐doped 6H‐SiC crystals is studied. Good agreement of theoretical calculations with the experimental results is obtained.
Raman spectra of a LiN(HxD1‐x)4SO4 mixed crystal
Authors: Torgashev V. I. , Yuzyuk Yu. I. , Smutný F. , Polomska M. 
Published: July 2007

AbstractRaman spectra of a deuterated lithium ammonium sulphate single crystal are studied at 77 to 493 K. The results show that the I‐II‐III phase transitions are bonded essentially with the dynamics of Li‐SO4 framework; the NH4‐spectra are of a diffusive character so that no clear‐cut conclusions can be drawn about the role of the NH4‐sublattice in these phase transitions. The spectra corroborate the necessity of using several order parameters in the phenomenological description of the phase transitions in this crystal.
Euler's formulae and sturm's sequence and the stimulating regions for stimulated raman effect in simple piezoelectric cubic crystals
Authors: Schulz V. , Merten L. 
Published: July 2007

AbstractStimulated Raman effect in simple piezoelectric cubic crystals only occurs in the so‐called “stimulating regions” of the dispersion curves. It is shown that, if the dispersion equation of the quasiparticle component is of fourth degree in the wave number, the number and position of the “stimulating regions” can be determined by Euler's form of the solutions and by the method of Sturm's sequence.
Pressure‐induced polymorphic phase transitions of potassium and rubidium halides
Authors: Puri U. , Kumar V. 
Published: July 2007

AbstractPressure induced phase transitions in potassium and rubidium halides are studied. The screened Coulomb type potential form is used alongwith improved values of van der Waals constants. Parameters of the potential are determined separately for both the structures. The results are in good agreement with experimental values in case of KCl and KBr and show improvement over other theoretical values.
Superionic phase transitions in hydrogen bonded crystals
Authors: Plakida N. M. 
Published: July 2007

AbstractA microscopic theory of phase transition in the protonic superionic conductors is proposed. By taking into account short‐range proton correlations on hydrogen bonds a order‐disorder Slater‐type phase transition of first order is obtained. Due to the linear coupling between the order parameter and lattice deformation the phase transition is ferroelastic with a soft elastic coefficient C11 ‐ C12.
γ‐Ray induced coloration of KCl:Eu2+ crystals
Authors: Opyrchal H. , Nierzewski K. D. , Macalik B. , Mladenova M. 
Published: July 2007

AbstractThe formation of color centres at RT in γ‐irradiated KCl crystals doped with Eu2+ ions in a wide concentration range is studied by optical absorption, thermoluminescence, and the ITC method. In contrast to the ordinary F‐band behaviour a decrease of the V2‐type band with increasing dopant concentration is observed. The thermoluminescence spectra reveal the presence of two glow peaks positioned at 363 and 453 K independently of the europium concentration. On the basis of the ITC measuremtens it is found that the number of F‐centres formed does not correlate with the number of the europium dipoles destroyed by irradiation for all samples studied. Moreover, optical and thermal bleaching of color centres F‐ and V2‐type is not accompanied by the recovery of europium dipoles. The results obtained are consistent with the previous model ascribing the decay of europium dipoles to a radiation‐induced aggregation process. It is proposed that the disappearance of the V2‐like band with dopant concentration is caused by the strong interaction of the europium clusters formed during irradiation with the halogen interstitials, drastically lowering the pertinent oscillator strength.
Curie temperature of a doped ferromagnetic semiconductor
Authors: Matlak M. , Skrobiś K. 
Published: July 2007

AbstractOn the basis of the s—f model (S = 1/2) a formula for the Curie temperature as a function of band filling and model parameters is derived. Taking the s—f coupling seven times greater as in the real case (S = 7/2) the comparison with experiments on doped EuO and EuS samples gives relative good agreement.Auf der Grundlage des s—f‐Modells (S = 1/2) wird eine Formel für die Curietemperatur als Funktion der Bandfüllung und Modellparameter entwickelt. Mit einer s—f‐Kopplung, die siebenmal größer als im Realfall ist (S = 7/2) gibt der Vergleich mit Experimenten an dotierten EuO‐ und EuS‐Proben relativ gute Übereinstimmung.