bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anomalous Temperature Dependence of Charge Carrier Density and Mott Transition in Ferromagnetic Semiconductors
Authors: Grigin A. P. , Nagaev E. L. 
Published: July 2007

AbstractThe temperature dependence of the conductivity of ferromagnetic semiconductors is theoretically investigated for both the non‐degenerate and degenerate case with allowance of the exchange interaction between moveable electrons and localized magnetic moments. For the former the temperaturedependence of the charge carrier density is found.
Charge Transfer in Some Transition‐Metal Semiborides
Authors: Kohm A. , Merz H. 
Published: July 2007

AbstractHigh‐resolution bremsstrahlung isochromats of the semiborides (FeCo)B, Co2B, (CoNi)B, Ni2B are presented. A systematic difference between the isochromats of the borides and those of the corresponding metals can be understood in a simple charge transfer model. Boron acts as donor and supplies (1.6 ± 0.5) electrons per boron atom.
Statistical Theory of the Interaction between Point Defects and Flux Lines
Authors: Schmucker R. , Kronmüller H. 
Published: July 2007

AbstractUnder special consideration of the magnetic terms, the micromagnetic theory of super‐conductivity is employed to calculate the interaction between flux lines and elastic dipoles. The interaction force between one flux line and one elastic dipole with cubic symmetry is given analytically. The average pinning force due to the interaction with many point defects isobtained by a statistical treatment which considers the spatial fluctuations in the dipole density and the flexibility of the flux lines.
Mean‐Square Ionic Displacements and Force Constants of Crystals with the CsCl Type Structure
Authors: Jex H. , Müllner M. , Dyck W. 
Published: July 2007

AbstractMean‐square vibrational amplitudes of ions in the diatomic lattices of crystals with the CsCl type structure have recently been determined in the high temperature region by elastic scattering of neutrons. An evaluation of mean‐square displacements in terms of frequency moments is derived and connections with the force constants of the crystals are worked out. The difference of the vibrational amplitudes of the two ions is calculated from the experimental data and by means of force constants derived from phonon measurements.
On the Equivalence of the Kubo Formalism and a Transport Equation Approach
Authors: Van Keer R. , Phariseau P. 
Published: July 2007

AbstractFrom an analysis on the equivalence of the Kubo formula for electrical conductivity and a transport equation approach for electrons in disordered systems, it is made clear that the decoupling assumptions, involved in the derivation of the macroscopic equations, are justified if Taylor's conditions are satisfied.
Galvano‐ and Thermomagnetic Phenomena in n‐InSb‐Type Semiconductors at Inelastic Optical Scattering
Authors: Tolpygo H. I. 
Published: July 2007

AbstractFollowing a previous work [1] the temperature and field dependence of the transport coefficients are calculated for non‐degenerated n‐InSb taking intoaccount Kane's dispersion law, inelastic optical scattering, and the temperature dependence of the band structure parameters. Preliminary calculations based upon the relaxation time approximation confirmed the conclusion [1] about the dominant role of the optical and impurity scattering (including that of electrons by holes) in a broad temperature interval (50 to 400 °K). The Boltzmann equation for this scattering mechanisms using the method developed in [2] is solved. The electron distribution functions were found for the cases of the electric and magnetic fields and the thermal flow being present. Theoretical results for the mobilities and the Nernst‐Ettingshausen (NE) coefficients are compared with the experiment. This comparison shows that the theory overestimates somewhat the role of the optical scattering. Both the absolute values and the temperature dependence of the NE coefficients turn out to be only in a rough correspondence with the observed ones. The possible reasons of discrepancies are discussed.
Herzberg‐Teller Interaction and Vibronic Coupling in Molecular Crystals I. The Simple Model
Authors: Zgierski M. Z. 
Published: July 2007

AbstractThe vibronic absorption spectrum of a molecular crystal, corresponding to the formation of an exciton in a state forbidden by the intramolecular symmetry, is investigated. It is assumed that intensity is borrowed from a higher electronic state with help of the Herzberg‐Teller mechanism. Non‐totally and totally symmetric intramolecular vibrations are included into this consideration. Formulae for relative intensities of different vibronic lines in the spectrum are obtained. The one‐ and two‐phonon regions of the spectrum are discussed.
Elastic Interaction of Small Defects and Defect Clusters in Hexagonal Crystals
Authors: Yoo M. H. 
Published: July 2007

AbstractAn analysis is given of the elastic interaction between small defects and/or defect clusters in hexagonal crystals. Simple explicit expressions for the interaction energy are obtained directly from the Green's function given by Kröner. Some typical calculated results are presented for various combinations of axially symmetric defects, e.g., a pair of point defects, a pair of dislocation loops, and a point defect and a dislocation loop. Applications to a study of Frenkel defects recombination processes in irradiated hexagonal crystals are discussed.
Anisotropy of Electron and Hole Masses and g‐Factors for PbSe by k · p Calculation
Authors: Bangert E. , Kästner P. 
Published: July 2007

AbstractAn ellipsoidal non‐parabolic k · p model (enp‐model) is used to calculate the anisotropy constant K = ml/mt and der transverse g‐factor g ⟂ for n‐ and p‐type lead selenide. These quantities are fitted to the experimental values by variation of only one parameter. For the anisotropy constants an excellent agreement could be achieved, whereas the computed transverse g‐factor turns out to be too large by about 30%.
Electric‐Field‐Modulated Reflectance on Tellurium
Authors: Herwig R. , Stuke J. , Weiser G. 
Published: July 2007

AbstractThe electroreflectance spectrum of tellurium single crystals (MOS structure) has been studied in the energy range between 0.3 and 3.2 eV and compared with the spectrum of selenium. Three transitions are observed below 0.5 eV which correspond to the threefold split valence band at point H of the Brillouin zone. The sequence of these energy bands is the same as in selenium and also the temperature shift of the gap shows a similar behaviour for both materials. At higher energies (ℏω > 1 eV), the spectrum of tellurium is much more complicated than that of selenium and a correlation to bandstructure calculations is only partially possible. The dependence of the electroreflectance response on a dc bias points to the existence of slow surface states at the interface tellurium–tellurium dioxide.
Magneto‐Microwave Kerr Effect in Semiconductors
Authors: Srivastava G. P. , Kothari P. C. 
Published: July 2007

AbstractA theoretical and the experimental study of magneto‐microwave Kerr effect has been done in terms of R, the amplitude ratio of the two orthogonal elliptically polarized components of the reflected wave and δ, the phase difference between them. A double microwave bridge technique (X‐band) has been employed for the experimental measurements. The magnetic field has been applied both parallel (Faraday configuration) and perpendicular (Voigt configuration) to the direction of propagation. The experimental results for R, in the Faraday configuration, on two n‐type germanium and two n‐type silicon samples compare well with the theory, while in the Voigt configuration, there is a discrepancy in the theoretical and experimental results. The probable reasons for this discrepancy have been discussed.
Temperature Dependence of the Specific Heat of Superconductors
Authors: Nowotny H. , Grau D. , Hittmair O. 
Published: July 2007

AbstractA dynamic one‐parameter model discussed in a previous paper is used to calculate the temperature dependence of the electronic specific heat of superconductors from the grand canonical potential. Deviations from the law of corresponding states are obtained and the numerical results show that the experimentally measured electronic specific heats of superconductors with strong or intermediate electron‐phonon interaction are very well reproduced. In particular the predictions of the model for the strong‐coupling superconductor lead are discussed.
Bound Electron States in the Strain Field of a 60° Dislocation in Germanium
Authors: Claesson A. 
Published: July 2007

AbstractDislocations in a crystal have a great influence on the states of electrons and phonons. As to electrons the effect of the dislocations is especially noticeable in semiconductors where the number of charge carriers normally is very small. The aim of the present paper is to find the potentials which describe the interaction between electrons and the strain field of a 60° dislocation in germanium. These potentials give rise to bound states with localized electrons.
A Theoretical Estimate of Acoustic‐Emission Stress Amplitudes
Authors: Malén K. , Bolin L. 
Published: July 2007

AbstractA theoretical estimate is made of the stress amplitude for acoustic emission due to the sudden local change of an inelastic strain. The source may thus be e.g. dislocation motion, crack propagation, twinning or martensitic transformation. The dynamic aspect of the acoustic emission event is emphasized. The estimates have been compared with some experimental results reported in the literature and a reasonable agreement is found.
Electronic Properties and Defect Structure of Ti407: Correlation of Magnetic Susceptibility, Electrical Conductivity, and Structural Parameters via EPR Spectroscopy
Authors: Houlihan J. F. , Mulay L. N. 
Published: July 2007

AbstractVariable temperature EPR studies of polycrystalline Ti4O7 and preliminary single crystal studies have been interpreted in relation to the static magnetic susceptibility, electrical conductivity and X‐ray diffraction data obtained on Ti4O7 samples from the same chemical run. This has facilitated the calculation of the mobility, the electrical conductivity, and the electronic effective mass in both the metallic and semiconducting regions of Ti4O7. Below ≈ 149 K a hopping mechanism dominates the conduction properties and at ≈ 120 K, μhop ≈ 4 × 10−6 cm2/Vs and σcal ≈ 1.49 × 10−3 (Ω cm)−1. This latter value is in good agreement with σmeas ≈ 3 × 10−3 (Ω cm)−1 obtained experimentally. An electronic effective mass of 5.6 me has been obtained for the semiconducting region and is consistent with a value of ≈ 5 me determined from thermoelectric and Hall effect data for the low temperature phase of Ti2O3. Above 149 K optical mode phonon scattering and ionized defect scattering combine to yield a total mobility of μT ≈ 0.6 cm2/Vs and σcal ≈ 1.43 × 103 (Ω cm)−1 which is in excellent agreement with the electrical conductivity results at 295 K.
Theory of Raman Scattering by Polaritons Due to Spatial Dispersion
Authors: Sindeev Yu. G. , Granovskii V. G. 
Published: July 2007

AbstractThe theory of Raman scattering (RS) by polaritons in the infrared range of frequencie‐when the optical nonlinearity of the crystal is due to spatial dispersion (SD) is develop ed. It is demonstrated that the RS in centrosymmetric crystals may be observed due to this nonlinearity. The RS cross section due to SD by the phonons and polaritons of lower and upper branches is calculated by a Green's function method. Anumerical estimate of the RS cross section due to SD is given for the case of sodium chloride.
The Polarised Raman Spectra of Ferroelectric and Non‐Ferro‐electric Potassium Lithium Niobate
Authors: Siapkas D. , Clarke R. 
Published: July 2007

AbstractThe polarised Raman spectra of two potassium lithium niobate compositions are presented. The first, a nearly stoichiometric ferroelectric version, K5.9Li3.8Nb10O30, exhibits a strongly temperature dependent A1(z) spectrum near the Curie point. This is held to be indicative of soft mode behaviour. The relationship between structural, dielectric and Raman measurements in this material is discussed. Measurements of the integrated intensity of the A1(z) modes, as a function of temperature, are presented and an estimation of the room‐temperature spontaneous polarisation is deduced. The A1(z) modes persist for tens of degrees above the Curie point indicating that there are regions of non‐zero polarisation within the crystal above the Curie point. No temperature dependence of the A1(z) mode frequencies is observed in K5.0Li2.4Nb10O30, a closely related non‐ferroelectric composition.
Herzberg‐Teller Interaction and Vibronic Coupling in Molecular Crystals. II. The Simple Model with Inclusion of a Frequency Change in the Non‐Totally Symmetric Vibration
Authors: Zgierski M. Z. 
Published: July 2007

AbstractThe simple model introduced in part I of this work, allowing for a theoretical investigation of symmetry‐forbidden vibronic absorption bands of molecular crystals, is extended in order to include the possibility of a frequency change of the non‐totally symmetric vibration which couples two molecular states with help of the Herzberg‐Teller mechanism. A formula for the absorption coefficient in the zero‐phonon approximation is derived and discussed. One‐ and two‐phonon regions of the spectrum are investigated.
Relativistic Theory of Low Energy Electron Diffraction: Application to the (001) and (110) Surfaces of Tungsten
Authors: Feder R. 
Published: July 2007

AbstractA relativistic theory for calculating low energy electron diffraction intensities and spin polarization properties is applied to the (001) and (110) surfaces of tungsten for several angles of incidence. Intensity‐energy profiles are obtained in generally good agreement with experimental data. Relativistic effects on intensities are found to be noticeable, and appreciable spin polarization features are predicted. In particular, large degrees of spin polarization in conjunction with sizeable intensities are found in the specular beam for large angles of incidence on W(001).
Perturbation Theory with a Non‐Complete Set of Hamiltonian Eigenstates
Authors: Potapkov N. A. 
Published: July 2007

AbstractA method is proposed of constructing a perturbation theory in which a non‐complete set of eigenstates of the non‐perturbated Hamiltonian is used. The expansion of the expectation value of the energy and magnetization of an anisotropic ferromagnet at T = 0 in powers of Ia/I is obtained. In this expansion the zero order, the first, and the second‐order terms are completely taken into account.
The Influence of Plasmon Damping on the Mean Free Path of Electrons for Plasmon Excitation
Authors: Ashley J. C. , Ritchie R. H. 
Published: July 2007

AbstractMany‐body theory is used to calculate the inverse mean free path for plasmon excitation by an electron in a free‐electron gas with damping of the plasmon states included. The theory is applied to the special case of Al for which experimental data on damping of the plasmons are available. Numerical calculations indicate an appreciable probability for exciting plasmons by incident electrons with energies below the threshold energy predicted by “no‐damping” theories.
Elastic Constants and Lattice Stability of Quantum Crystals
Authors: Plakida N. M. , Aksienov V. L. 
Published: July 2007

AbstractOn the basis of the self‐consistent theory the elastic constants are calculated and the region of lattice stability of quantum crystal is found for a simple model with a f.c.c. lattice. It is shown that the second order terms in the self‐consistency equation play an essential role and should be taken into account for the correct description of the quantum crystals.
Mössbauer Spectra of (NH4)2SbxSn1−xCl6 Crystals
Authors: Yu. Aleksandrov A. , Ionova G. V. , Ionov S. P. , Baltrunas D. A. , Makarov E. F. 
Published: July 2007

AbstractMössbauer spectra of mixed (NH4)2SbxSn1−xCl6 crystals with x = 0.02, 0.06, 0.08, 0.19, 0.24, and 0.28 were investigated in the temperature range 77 to 150 K. On the basis of the obtained data a packing model of the mixed crystals is proposed. A transition is found in the crystal with x = 0.28: below a critical temperature region Sb3+ and Sb5+ ions are ordered and above they have the average valence of Sb4+. This transition is interpreted on the basis of the co‐operative interaction of electron pairs.
Optical Constants and Electronic Structure of Crystalline and Amorphous As2S3 in the 3 to 35 eV Range
Authors: Perrin J. , Cazaux J. , Soukiassian P. 
Published: July 2007

AbstractBy Kramers‐Kronig analysis, the complex dielectric constant tensor of monocrystalline As2S3 is deduced from energy losses in the 3 to 35 eV range suffered by a 40 keV electron beam. The weak optical anisotropy observed in this spectral range is explained and the results are discussed in terms of a valence bonding model with two groups of valence bands. Upon the amorphous to crystalline transition it is the optical transitions originating in the resonance bonds which are only influenced.
Optical Effective Mass of Holes in p‐Type AIIIBV Compounds
Authors: Filipchenko A. S. , Nasledov D. N. , Radaikina L. N. 
Published: July 2007

AbstractA comparative study is made of the concentration dependences of the optical effective masses of holes in a series of p‐type AIIIBV compounds. It is shown that in all compounds studied the optical effective mass of holes begins to increase under high concentrations of carriers. A qualitative explanation is given of such increase. The comparison of the concentration dependences of mp for various compounds shows that the valence bands are similar in various AIIIBV compounds. The structure of the valence bands in AIIIBV compounds is substantially different from the structure of the conductivity bands. Therefore in theoretical calculations of different effects it is necessary to distinguish quite distinctly the dependences on the density‐of‐states effective mass and on the conductivity effective mass, i.e. to be very cautions in the use of the quasiisotropic band approximation.
Long‐Wavelength Optical Phonons in K1−xTlxCl and K1−xTlxBr Mixed Crystals
Authors: Bauhofer W. , Genzel L. 
Published: July 2007

AbstractThe q ≈︁ 0 lattice vibrations of mixed crystals of K1−xTlxCl and K1−xTlxBr have been observed by far infrared reflectivity measurements. Contrary to the existing assumption, the system K1−xTlxCl clearly shows a mixed‐mode behaviour similar to that of K1−xRbxI. K1−xTlxBr is either a mixed‐ or a two‐mode system. The experimental results are in good agreement with a modified version of the REI‐model.
Magnetische Bereichsstrukturen in Typ‐I‐Dünnschichtsupraleitern. I. Der Zwischenzustand
Authors: Kunze U. , Lischke B. , Rodewald W. 
Published: July 2007

AbstractDie magnetflußerfüllten Bereiche in dünnen supraleitenden Schichten (Pb, In) in senkrechten Magnetfeldern wurden durch die Dekoration mit Eisenteilchen sichtbar gemacht. Die Abhängigkeit dieser Zwischenzustandsstrukturen von der Schichtdicke wurde mit theoretischen Modellen verglichen. Unterhalb einer kritischen Schichtdicke von etwa dc ≈︁ 0,1 μm wird ein Übergang von den Strukturen des Zwischenzustandes zum zweidimensionalen Mischzustand beobachtet.
Effects of Doping on the Condensed Electron–Hole State in Germanium and Silicon
Authors: Martin R. W. , Sauer R. 
Published: July 2007

AbstractRadiative recombination in electron‐hole drops has been investigated for doping levels up to ≈︁1018 cm−3 in Ge and Si. It was found that the energy of the condensed state and the density of electrons and holes become dependent on excitation and on impurity concentration above 1016 cm−3. Characteristic differences of the lineshapes for the case of Ge and Si are discussed.
EPR of BaCl2:Gd3+
Authors: Oosterhoff T. , Den Hartog H. W. 
Published: July 2007

AbstractThe g‐value and the most important crystal field parameters of Gd3+ in orthorhombic (D) BaCl2, are determined at room temperature: g = 1.994 (isotropic), b = ± 90 × × 10−4 cm−1, and b = ∓444 × 10−4.cm−1. The corresponding theoretical values are g = 1.993, b = 85 × 10−4 cm−1, and b = −324 × 10−4 cm−1. A comparison of the results with values for Eu2+ and Gd3+ ions at Pb2+ sites in PbCl2, and PbBr2, is made.
Quantum‐Mechanical Study of Rosette‐Motion Channeling
Authors: Tamura A. , Ohtsuki Y. H. 
Published: July 2007

AbstractQuantum mechanical treatment of the “Rosette‐Motion” channeling of energetic electron beams is developed. Energy levels and scattering angles corresponding to channeling are determined. Detailed calculations are performed for W〈111〉 for various energies. The lifetime of such quantum states is discussed making use of the mean free path due to lattice vibrations.
Shape of the Cyclotron Resonance Absorption Line of Polar Semiconductors: n‐InSb at 337 μm
Authors: Palmetshofer L. , Kranzer D. 
Published: July 2007

AbstractThe shape of the cyclotron resonance absorption line of n‐InSb samples is investigated. Experiments were carried out using a HCN laser beam. The temperature range considered being 77 to 150 K. According to the preparation of the sample surface different shapes of the absorption line are observed. Additionally a theory is worked out which is based on an exact numerical solution of the time‐dependent Boltzmann equation. The theoretical results are compared with the experiment.
Obtaining a Consistent Set of Thermodynamic Variables for Real Superconductors
Authors: Bostock J. , Mathews W. N. , Gregory W. D. 
Published: July 2007

AbstractA method is presented for obtaining a consistent set of thermodynamic parameters and temperature‐dependent thermodynamic variables for a real superconductor. The method depends upon determining a temperature‐dependent effective interaction strength for the particular material. Conversely, given the effective interaction strength for the superconductor, the thermodynamic variables as functions of temperature can be obtained. The method is illustrated for Al, V, Ta, Nb, and Pb. The results of this approach and the McMillan theory of the critical temperature are compared for Nb, Pb, and the In‐Tl alloy system.
On the Existence of Antiferrormagnetism in Half‐Filled Narrow Energy Bands
Authors: Lindner U. , Hewson A. C. 
Published: July 2007

AbstractIt is shown that the spin‐dependent shift of the subbands considered by Roth for the treatment of ferromagnetic solutions of the Hubbard model plays a decisive role in making antiferromagnetism possible on this model. A relation is given which allows to calculate the Néel temperature TN for a simple cubic lattice and a half‐filled band in dependence on the parameters of the Hubbard model and which includes in the limit a criterion formerly obtained by the simple Hubbard decoupling.
Effect of a Brownian Sublattice on Polariton Dispersion
Authors: Merten L. , Andrade P. Da R. 
Published: July 2007

AbstractA set of coupled equations describing the effect of a disorder mechanism on polariton dispersion is given. The treatment differs from that one finds in the literature because the disorder mechanism is not taken as a second‐order perturbation. A particular solution of these coupled equations shows that all originally undamped polaritons become damped waves. They all shift in frequency. Physical properties of different wave types in an order‐disorder crystal are discussed. For the complex frequencies of the coupled waves a modified Kurosawa relation and a modified LST relation is valid. Numerical evaluations of this model shall be given in a forthcoming paper.
Electron Spin–Lattice Relaxation Measurements of the Jahn‐Teller Complex Cu(6H2 O)++
Authors: Lee K. P. , Walsh D. 
Published: July 2007

AbstractSpin–lattice relaxation measurements at microwave frequencies in the liquid helium temperature range yield relaxation rates which are four orders of magnitude faster than the corresponding rate in a system without Jahn‐Teller complications. The results also emphasize that Jahn‐Teller parameters for this system cannot be determined to‐date with any certainty.