bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Magneto‐Optical Effect Under a Strong Electric Field in Semiconductors
Authors: Stramska H. 
Published: July 2007

AbstractA magneto‐optical effect theory based on the nonlinear Boltzmann equation is derived in the presence of a strong dc electric field. The addition of a phenomenological energy relaxation term to the Boltzmann equation provides analytical expressions for the magnetoconductivity in the limit of a quadratic deviation from Ohm's law. The current density is derived for a strongly degenerate electron gas, with an energy dependence of the momentum relaxation time. The Faraday rotation and ellipticity in a strong dc electric field are calculated.
Point Defect Aggregates in γ‐Irradiated LiF Single Crystals
Authors: Frugoli P. A. , Pimentel C. A. 
Published: July 2007

AbstractDiffuse X‐ray scattering near the Bragg reflection and Bragg line profile analyses are made in γ‐irradiated LiF single crystals using a double crystal X‐ray diffractometer. A preferential alteration in the profile parameters is noted. Clusters with mean parameter sizes from hundreds to thousands of angstroms are observed but each sample presents a set of average size values. The nature of the clusters is found to depend on the γ‐dose: vacancies at low dose (≈︁ 10 Mrd) and interstitials at high dose (≈︁ 50 Mrd). Some process of coalescence at 50 Mrd seems to occur.
On the Influence of Tunneling States on the Transition Temperature of Metallic Glassy Superconductors
Authors: Drechsler S. L. , Vujičič G. M. 
Published: July 2007

AbstractEstimates for the transition temperature Tc of amorphous superconductors taking into account both electron–phonon and electron–two‐level system (TLS) interactions are obtained. Using experimental data for metallic glasses like PdZr it is found, that the electron–TLS interaction gives quite an observable effect in the Tc‐increase.
Bistability of the Electron‐Hole Plasma Density in a Strong Electromagnetic Field
Authors: Harbich Th. , Mahler G. 
Published: July 2007

AbstractDiffering from the usual treatment of an electron‐hole plasma in quasi‐thermal equilibrium, where the particle density is kept constant, a plasma is considered with a fixed chemical potential. Such a situation is expected to be realistic for semiconductors with a direct gap in the presence of a strong monochromatic electromagnetic field. The appearance of a bistability in the plasma density is predicted for photon energies in the vicinity of the gap.
Investigation of the Electronic Structure of TihX and Ti1−Y VYHX by Positron Annihilation
Authors: Dębowska E. 
Published: July 2007

AbstractThe annihilation parameter changes as function of x and y are studied for TiHx and Ti1−yVyHx systems. The interpretation of the results is based upon s‐ and d‐like electron number changes. The conclusions, being in agreement with the band structure calculation results, confirm the uselessness of the rigid band approximation. The Jahn‐Teller effect, suggested by other authors as the γ → δ transition mechanism, finds its justification in the light of the present results, too. Especially interesting seems to be the way in which s‐ and d‐bands are occupied for different x in the cubic phase.
Hyperfine Field Investigations in Some Ru and Rh Based Heusler Alloys
Authors: Patil V. S. , Pillay R. G. , Tandon P. N. , Devare H. G. 
Published: July 2007

AbstractThe hyperfine fields at 57Fe and at 119Sn doped as a dilute impurity replacing Ge, in the new Heusler alloys Ru2FeGe and Rh2FeGe, are reported. The Mössbauer spectra at 119Sn indicate preferential RGe (R = Ru, Rh) disorder like in other Ru and Rh based Heusler alloys. The hyperfine field value is consistent with recent predictions based on the Blandin and Campbell model.
Optical Orientation and Polarized Luminescence in Silicon
Authors: Efanov A. V. , Entin M. V. 
Published: July 2007

AbstractThe polarization properties of the recombinative photoluminescence of free electrons excited to the conduction band of a cubic multivalley semiconductor by linearly and circularly polarized light are studied theoretically. The electron transitions from the valence band and impurities to the valleys of the conduction band are considered. The phonon‐assisted and phononless indirect transitions are taken into account. Unlike the case of semiconductors with direct interband transitions polarized light is emitted not only by hot electrons but also by cold ones, and by excitons.
Theory of Free–Carrier Absorption in n‐Type Lead Chalcogenides Due to Electron‐Electron Scattering
Authors: van Huong Nguyen 
Published: July 2007

AbstractThe theory of the infrared absorption by free carriers in lead chalcogenides of n‐type due to electron‐electron (e–e) interaction is discussed within the model of multivalley, nonspherical, and parabolic conduction band. Only the e‐e scattering of electrons of different valleys contributes to the absorption. A formula for the absorption coefficient for an arbitrary anisotropy of the valleys is derived.
Analyse du spectre d'absorption infrarouge de BaF2: Y3+
Authors: Jeandel G. , Warin A. , Morlot G. 
Published: July 2007

AbstractLe formalisme des fonctions de Green permet de déterminer les modes résonnants induits par la présence d'un cation de substitution dans le réseau du fluorure de baryum. Cette théorie nous a permis d'interpréter la différence observée entre nos spectres d'absorption infrarouge de BaF2:Y3+ et ceux de BaF2 activé par des ions de terres rares.
On the Kinetics of a Paramagnetic Oxygen Centre in CaF2
Authors: Fuchs H. J. , Karthe W. , Börner S. 
Published: July 2007

AbstractIn calcium fluoride crystals, doped with oxygen, centres of the VK type are generated at T = 77 K by X‐irradiation. The VK type centres recombine at T ≈ 150 K and paramagnetic oxygen fluorine‐vacancy centres (O–FV)− originate in the same concentration due to hole transfer whereas X‐irradiation at T = 300 K generates the (O–FV)− centres directly. The generation kinetics and optical and thermal bleaching of the centres are investigated. The activation energy of thermal bleaching EA ≈ 0.6 V indicates a fluorine‐vacancy mechanism. The oxygen diffusion in undoped CaF2 is studied by means of the (O–FV)− centres. The activation energy of the diffusion amounts to E = (1.8 ± 0.2) eV, the diffusion constant D0 depends on the crystal lattice defects.
Surface‐Ripple Brillouin Scattering from a Glass–Metallic Liquid Interface
Authors: Albuquerque E. L. 
Published: July 2007

AbstractA theoretical calculation is presented for the Brillouin lineshapes of a glass‐metallic liquid interface. The theory takes into account only the surface‐ripple mechanism for the cross section since it is the dominant mechanism for opaque materials. In the Brillouin spectrum the contribution is shown from the surface acoustic wave of the Stoneley type. A comparison between the theoretical results and the experimental spectrum is also done and they are in a good agreement.
Density Functional Approach for Metals. The Matheiss Prescription
Authors: Ghosh A. K. , Chakraborty S. , Manna A. 
Published: July 2007

AbstractCharge densities of free atoms modify to a great extent when they form metallic systems. This modification is examined in this paper in the light of Löwdin's α‐expansion formalism as adopted by Matheiss in his muffin‐tin potential calculation. Wigner‐Seitz radius and cohesive energy of copper are calculated through the density functional approach by using this modified charge density. Charge densities at the cell boundaries of 3d transition metals are also calculated to test the applicability of the method to all metals. The results are quite encouraging, the simplicity of the method notwithstanding.
Thermopower of Bismuth in Low Longitudinal Magnetic Fields
Authors: Vašk P. , Svoboda P. 
Published: July 2007

AbstractThe thermopower of a Bi single crystal is measured at temperatures below 8 K and in longitudinal magnetic fields up to 0.014 T. The change of the thermopower α(B) due to the magnetic field isfound to be negative below about 5K and positive above. This behaviour can be understood on the basis of the standard theory of the phonon‐drag thermopower and the temperature dependence of partial thermopowers can be estimated.
Hall Coefficient and Magnetoresistance of Semiconductors with Anisotropic Energy Dispersion
Authors: Tomchuk P. M. , Shenderovskii V. A. , Gorley P. N. , Gavaleshko N. P. 
Published: July 2007

AbstractHall coefficient and transverse magnetoresistance of narrow‐gap semiconductors are investigated theoretically in a wide temperature region. It is shown that in a weak magnetic field the transport coefficients exhibit non‐monotonic temperature dependence and in arbitrary classical magnetic fields the transverse magnetoresistance may grow anomalously. These regularities are due to inelastic scattering of carriers by optical phonons and anisotropy of the temperature dependences of the components of the effective mass tensor. The contributions which different scattering mechanisms (those by acoustic phonons, impurity ions, and interelectron scattering) give to the transport coefficients are evaluated. In particular, the contributions of impurity and interelectron scattering processes are shown to be negligibly small in lead chalcogenides.
Direct Determination of Indium Antimonide Energy Band Parameters from Diamagnetic Exciton Spectra
Authors: Kanskaya L. M. , Kokhanovskii S. I. , Seysyan K. P. , Efros Al. L. 
Published: July 2007

AbstractDiamagnetic exciton spectra of InSb crystals derived from transmission measurements carried out on thin unstressed samples at 1.8 K and in magnetic fields up to 80 kOe are used for a direct determination of parameters of the c‐ and v‐bands. Detailed identification and precise binding energy calculations permit one to derive the cyclotron frequencies of the electron and the holes, and the spin splittings. The m(ϵc) and g(ϵc) relationships thus obtained exhibit good agreement with Kane's model up to energies close to ϵc ϵg. Light holes also reveal a strong nonparabolicity characterized in the linear‐in‐k4 approximation by the coefficient p1h = 0.47 meV−1. An analysis of the splitting of two light‐hole long‐wavelength transitions including the diamagnetic exciton binding energies and the data on the c‐band obtained permits one to calculate the v‐band parameter set.
Two Types of F Centres in Alkaline Earth Fluoro‐Halides. I. Superhyperfine Interactions and Electronic Structure
Authors: Bauer R. U. , Niklas J. R. , Spaeth J.‐M. 
Published: July 2007

AbstractIn the alkaline earth fluoro‐halides BaFCl, SrFCl, and SrFBr two types of F centres with different symmetry are produced, where the electron occupies either an F− vacancy (F(F−) centres) or a Cl− or Br− vacancy (F(Cl−, Br−) centres), respectively. With electron nuclear double resonance the superhyperfine and quadrupole interactions with up to nine shells of neighbour nuclei are determined. The spin density distribution is rather anisotropic. For F(Cl−) centres it can be explained with an 1s‐type centre wave function if the mutual overlap of the lattice ions is taken into account. For the F(F−) centres a small admixture of a 2p‐ or a 3d‐type orbital to the 1s function is required.
Variational Calculations for Ground‐State Energies of Donor–Acceptor Pairs
Authors: Englisch R. 
Published: July 2007

AbstractFor the calculation of ground‐state energies of donor‐acceptor (DA) pairs (and also of two related three‐body problems) variational ansatzes are tested including the correlation between electron and hole. A refinement of a paper by Kartheuser et al. is presented for small distances of the DA pairs. Further, another method to solve the integrals occurring is shown which avoids numerical integration.
The Influence of the Structure of Different Arsenic Chalcogenide Glasses on Refractive Index and Dispersion
Authors: Burckhardt W. , Feltz A. 
Published: July 2007

AbstractThe refractive index dispersion of different arsenic chalcogenide glasses is analyzed by the use of a two‐term Sellmeier dispersion formula. In a region from 3 μm up to the beginning of the absorption edge the wavelength dependence of the refractive index can be described by a single oscillator model. At wavelengths λj, determined by λ1j, = const, the molar refraction of the different glasses is a linear function of neff λ. In representations RM = RM(neff) and RM = RM(λ) the influence of the structure of the different glasses is clearly illustrated. For the glass AsSe3 a special short‐range order is indicated.
Towards a Molecular Theory of the Solid–Liquid Phase Boundary. Structural Theory and Effective Lattice Models
Authors: Klupsch Th. 
Published: July 2007

AbstractFrom the molecular, structural theory, an unrestricted quadratic Ising model is derived the subcritical region of which enables a semi‐quantitative description of the f.c.c. crystalline phase in coexistence with its melt including the interface between them for simple one‐component systems with small melting heat at thermal equilibrium, especially for Lennard‐Jones systems near the triple point. The Ising Hamiltonian is determined by the free excess energy and not by the internal energy; except of the melting heat, it involves contributions from the entropy difference connected with the higher degree of disorder of liquids compared with the crystalline state. Therefore, a remarkably large Jackson‐Temkin factor of about three results, but it does not uniquely determine the interface structure because the effective interaction is not restricted to next‐neighbouring lattice sites. A new interpretation of the wetting condition in terms of the effective potential is presented.
Determination of Stresses in SiSiO2 and Mechanically Affected Si by EPR
Authors: Gehlhoff W. , Segsa K. H. 
Published: July 2007

AbstractThe influence of stresses generated by roughening or oxidation of silicon samples on the EPR spectra of Fe0 in silicon is investigated. Starting from previous calculations it is possible to explain the changes in the angular dependence of the spectra, and to determine the stress components in the SiO2 film and in the Si surface affected by roughening. The stress values determined by the EPR analysis are compared with the results obtained by other methods.
Renormalized Atom Model (RAM) Applied to the Heavy Rare‐Earth Sesquioxides in Cubic Crystal Structure
Authors: López‐Aguilar F. , Costa‐Quintana J. 
Published: July 2007

AbstractThe electronic structure of the b.c.c. heavy rare‐earth sesquioxides is analyzed through the singlesite solutions within the renormalized atom model (RAM) and using the relativistic version. The Coulomb correlation energy is calculated in order to determine the unoccupied 4f levels.
Precise Positron Lifetime Measurements in Indium
Authors: Puff W. , Mascher P. , Kindl P. , Sormann H. 
Published: July 2007

AbstractThe positron lifetime is measured in polycrystalline indium in the temperature range between 80 and 420 K. The data show a pronounced prevacancy effect which is fairly well approximated by a straigth line. The results suggest transient dilatation trapping rather than metastable self‐trapping. The occurrence of this effect has some influence on the values deduced for the monovacancy formation enthalpy. In the temperature range below 180 K detrapping of positrons cannot be ruled out.
Diffusion‐Induced Quadrupole Relaxation of 27Al Nuclei in Dilute AlTi, AlCr, AlMn, and AlCu Alloys at High Temperatures
Authors: Bottyán L. , Beke D. L. , Tompa K. 
Published: July 2007

AbstractThe temperature dependence of the laboratory frame spin‐lattice relaxation time of 27Al nuclei is measured in 5N Al and in dilute AlTi, AlCr, AlMn, and AlCu alloys at 5.7 and 9.7 MHz resonance frequencies. The relaxation in pure aluminium is found to be purely due to the conduction electrons. An excess T1‐relaxation contribution is detected in all Al–3d alloys investigated above 670 K. The excess relaxation rate is proportional to the impurity content and the temperature dependence of the excess contribution is of Arrhenius‐type with an activation energy of (1.3 ± 0.3) eV for all of the investigated alloys. The relaxation contribution is found to be quadrupolar in origin and is caused by the relative diffusional jumps of solute atoms and Al atoms relatively far from the impurity.
Two‐photon interband absorption of light in semiconductors in external parallel electric and magnetic fields
Authors: Katana P. K. 
Published: July 2007

AbstractThe constant of the two‐photon interband absorption of light (TPA) in a semiconductor placed in external, parallel quantizing electric and magnetic fields is calculated. It is shown that the TPA constant near each Landau level must have an oscillatory behaviour due to the presence of discrete Stark levels, that is, at high electric field strengths the “Stark ladder” must be observed. The following particular cases are considered: the one‐photon absorption (OPA), the two‐photon electroabsorption (TPEA), and the two‐photon magneto absorption (TPMA).
The polariton soliton formation due to the effect of the dipole momentum saturation
Authors: Shibarshina G. D. , Moskalenko S. A. , Khadzhi P. I. 
Published: July 2007

AbstractThe energy flux density of the incident light upon the crystal surface and the form of the wave packet envelope with frequencies lying in the exciton range of the spectrum, are determined. They must be of such a nature that after the penetration into the semi‐infinite crystal, the laser pulse can travel at once as a solitary wave without any transient stage. In the case considered the effect of the dipole momentum saturation (DMS) for the transition from the ground state of the crystal to that of the exciton is the main nonlinearity. The Maxwell‐Fresnel boundary conditions are used on the interface between the vacuum and the crystal.
On incommensurate phases in the magnetic phase diagram of the hubbard model
Authors: Schumacher W. 
Published: July 2007

AbstractThe existence of “heat magnetization” in the antiferromagnetic phase of the Hubbard model is discussed in connection with the occurrence of incommensurate magnetic phases. A magnetic phase diagram is derived for temperatures T > 0 in the framework of the Hartree‐Fock approximation. In a great region of this phase diagram incommensurate phases exist. For certain parameters there occurs a phase transition from the incommensurate to the antiferromagnetic phase if the temperature is increased.
Isovalent‐impurity clusters in koster‐slater approximation
Authors: Goede O. , Hennig D. 
Published: July 2007

AbstractThe binding energies of an electron (hole) bound to an m‐atomic isovalent‐impurity cluster in crystals with f.c.c. or h.c.p. cation (anion) sublattices are calculated in a Koster‐Slater one‐band one‐site approximation using Green's function technique. The conduction (valence) band of the host crystal is described by an one‐band tight‐binding Hamiltonian. The binding energies εm, μ are obtained for the ground and excited states of the various types μ of the clusters with respect to the number of nearest‐neighbour steps between the impurities as functions of J/T, where J is the Koster‐Slater parameter and T the effective conduction (valence) band width. The calculated energies using a Hubbard density of states (model H) or a Bethe‐lattice approach for the Green's functions (model B) are discussed and compared with experimental results for CdS: Te and GaP:N.
Local heine‐abarenkov model potential for III–V and II–VI covalent compounds
Authors: Soma T. , Kagaya H.‐Matsuo 
Published: July 2007

AbstractA local Heine‐Abarenkov model potential is proposed for zincblende‐type crystals. The potential parameters are determined by satisfying the zero pressure condition and the first zero of the empirical pseudopotential interpolated from band calculations. Two sets of parameters are presented for thirteen tetrahedral compounds such as AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, ZnS, ZnSe, ZnTe, and CdTe.
Optical Detrapping in Molecular Crystals. I. Vibrational Structure of Detrapping Transitions
Authors: Petelenz P. 
Published: July 2007

AbstractA simple model of optical detrapping in molecular crystals is proposed. It includes the coupling of electronic and vibrational degrees of freedom, due to the displacement of the equilibrium position in intramolecular vibrations upon ionization or electronic excitation of the molecule. The coupling is shown to shift the apparent distribution of trap depths towards greater values. Possible relevance of the model to the interpretation of experimental data is discussed and new experiments are suggested.
Image Forces at the Metal Electrode‐Electrolyte Solution Interface: Account of Spatial Dispersion of the Solution Permittivity
Authors: Rubinshtein A. I. 
Published: July 2007

AbstractThe effect of spatial dispersion of the permittivity of an electrolyte solution on the character of image forces W(a) near a metal electrode is investigated. The effect of penetration of an electric field into the metal is taken into account. The asymptotic expressions obtained for W(a) show that in highly dilute electrolyte solutions the charge in addition to usual attraction encounters an effective repulsion in two distance regions from the metal, so that the image of W(a) has an essentially non–monotonic form. For a more concentrated solution, the image of W(a) is modified and may take a form corresponding to a monotonic repulsion of the charge from the interface.
The Theory of Dynamical X‐Ray Diffraction on a Superlattice
Authors: Khapachev Yu. P. 
Published: July 2007

AbstractA general theory is given of dynamical X‐ray diffraction on a superlattice. The approach is based on an analysis of the solution of the Takagi equation system. Diffraction for two types of super‐lattices: T « ∧ and T ≈ ∧. (T period of superlattice, ∧ extinction length) is considered. Angle position of satellites and their widths are essentially different from analogous results of the kinemetical theory.
Temperature Dependence of ESR Spectra of Doped Amorphous Germanium
Authors: Stutzmann M. , Stuke J. 
Published: July 2007

AbstractThe temperature dependence of g‐value, linewidth, spin density, and spin‐lattice relaxation time are investigated for the three different paramagnetic states in doped amorphous germanium prepared by the glow discharge technique. The dangling bond resonance shows no temperature dependence of g‐value and linewidth. For the resonance due to localized electrons in the conduction band tail the g‐value and particularly the linewidth increase with temperatures above 150 K in highly phosphorus‐doped samples. The increase in linewidth is attributed to the coupling of the spins to electrons in extended states resulting in short spin‐lifetimes. For the resonance of localized holes in the valence band tail, however, g‐value and linewidth decrease above 100 K. In this case the lifetime broadening is overcompensated by a decrease of the g‐spectrum linewidth. From the temperature dependence of the spin density Ns the effective correlation energy U of the three states is derived. In the case of the dangling bonds the value U = 0.1 eV obtained from the energy dependence of Ns is confirmed. The corresponding values for holes and electrons localized in the band tails are 20 to 30 and 5 to 10 meV, respectively. The spin‐lattice relaxation time shows for dangling bonds and localized holes a T−2 temperature dependence down to 5 K which is attributed to two level systems modulating the spin‐orbit coupling. For electrons in the conduction band tail below 15 K a T−7 dependence is observed.
The Relativistic Linear Muffin‐Tin Orbital Method Application to Au
Authors: Nemoshkalenko V. V. , Krasovskii A. E. , Antonov V. N. , Antonov Vl. N. , Fleck U. , Wonn H. , Ziesche P. 
Published: July 2007

AbstractStarting with the Dirac equation the relativistic version of the linear muffin‐tin orbital method (RLMTO) is developed. It is considerably faster than the non‐linear RAPW method. Application to the band structure of Au shows, that the results (valence band energies) of both methods deviate in the average by only 0.004 Ryd from each other.