bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of the Quantum Hall Effect of the Two‐Dimensional Electron Gas in the n‐Inversion Layer of InSb Grain Boundaries under High Hydrostatic Pressure
Authors: Kraak W. , Nachtwei G. , Herrmann R. , Gliński M. 
Published: July 2007

AbstractThe magnetotransport properties of the two‐dimensional electron gas (2DEG) confined at the interface of the grain boundary in p‐type InSb bicrystals are investigated. Under high hydrostatic pressures and in high magnetic fields (B > 5 T) the integral quantum Hall regime is reached, where the Hall resistance ϱxy is quantized to h/e2j (j is the number of filled Landau levels of the 2DEG). In this high field regime detailed measurements are given of the resistivity ϱxx and the Hall resistance ϱxy as function of temperature T and current density jx. An unexpected high accuracy of the Hall resistance ϱxy at magnetic field values close to a fully occupied Landau level is found, despite the high value of the diagonal resistivity ϱxx. At high current densities jx in the quantum Hall regime (j = 1) a sudden breakdown of the quantized resistance value associated with a jump‐like switching to the next lower quantized value h/2e2 is observed. A simple macroscopic picture is proposed to account for these novel transport properties associated with the quantum Hall effect.
Theory for n‐Surface Charge Layers in Hg1−xCdxTe MIS Structures
Authors: Zöllner J.‐P. , Paasch G. , Gobsch G. , Übensee H. 
Published: July 2007

AbstractThe energy gap of the Hg1−xCdxTe‐system can be controlled by the mole fraction x of Cd. This offers the possibility to use this material as a model system for systematic investigations especially in the narrow‐gap region (corresponding to 0.16 ≦ x ≦ 0.25). The electronic structure, subband occupations, subband energies, and cyclotron masses are calculated for the two‐dimensional electron gas in MIS structures with this material using an approximate self‐consistent method. Both, inversion and accumulation conditions are considered. Comparisons with existing limited theoretical results and with experimental ones a) show the accuracy of the method used and b) allow to interpret the detailed experimental results from Shubnikov‐de Haas and cyclotron measurements available now. Predictions are made on the composition dependence of the electronic structure especially for inversion conditions.
Non‐Equilibrium Spin Polarization of the Si‐S1 Centre in Silicon Induced by Spin–Orbit Coupling
Authors: Minaev B. F. , Serebrennikov Yu. A. , Rempel H. D. 
Published: July 2007

AbstractElectronic structure calculations of the neutral charged oxygen‐substitutional impurity in silicon are carried out within the framework of the semi‐empirical MINDO/3 method. The structure of the substitutional impurity in the silicon lattice is simulated by finite molecular cluster OSi4H12 with an equilibrium SiH bond length 0.152 nm. Account of electronic interaction for single and double excitations allows to explain the nature of the impurity displacement in silicon. The cluster choosed serves as a good model for Si‐S1 centres. The results of spin–orbit coupling calculations give information about processes determining the appearance of non‐equilibrium spin polarization in these centres. The quantitative interpretation of Si‐S1 centre ESR‐spectra angular dependence in the helium region of temperature is carried out on the basis of the solution of the equation of motion for a triplet density operator. The dependence of the stationary concentration of triplet centres on magnetic field and crystal orientation is obtained.
IR Absorption Peaks and Oxygen Vacancies in YBa2Cu3Ox
Authors: Shi T. S. , Zhao Y. G. , Cai P. X. , Gu H. F. , Xie L. M. 
Published: July 2007

AbstractThree absorption peaks (620 to 640, 590, 550 to 580 cm−1) are observed in the IR spectra of YBa2Cu3Ox. The variation of intensity and frequency of these peaks with annealing temperature and oxygen content is investigated. The nature of IR peaks is studied and assignment to various CuO bond‐stretching vibrations is made and supported by the correspondence between peak frequency and appropriate CuO bond‐length. Based upon the correlation between peak intensity and oxygen content, these peaks are further interpreted as “quasilocalized” vibration mode of the CuO bond induced by the oxygen‐vacancy in the one‐dimensional CuO chain and two‐dimensional CuO network. The corresponding vacancy formation energy is found to be 0.34 and 0.93 eV, respectively. These peaks may serve as an useful indicator of oxygen content, crystal structure, and superconducting properties of YBa2Cu3Ox.
Elastic Constants and Phonon Spectra of Alkali Metals. Dynamical Treatment with Temperature‐Dependent Two‐Body Interaction
Authors: Singh N. , Banger N. S. , Singh S. P. 
Published: July 2007

AbstractAn exponentially damped two‐body interaction obtained in second‐order perturbation theory using a rational dielectric function and Heine‐Abarenkov model potential is used to calculate the elastic constants of alkali metals. The interaction is also used to predict the cohesive energy of these solids and the phonon spectra of rubidium. The agreement between predicted and observed values is as good as obtained with the corresponding theory for simple metals. The temperature dependence is included through a damping factor as obtained by Takanaka and Yamamoto.
Difference Equations in the Theory of Biphonons
Authors: Jäger E. , Mossa M. , Hehl K. 
Published: July 2007

AbstractUsing the method of difference equations the bound states of excitations in a linear chain are investigated. It is possible to obtain solutions of the partial difference equations and the energy of “biphonons” by a separation ansatz. The method of power series expansion is not so successful. The spectrum of the states with two phonons in two coupled linear chains (as a model of the system film‐substrate) is investigated additionally.
Optical Properties of Quasi‐1D n‐Merized Molecular Semiconductors
Authors: Yartsev V. M. 
Published: July 2007

AbstractInteracting dimers and trimers in quasi‐one‐dimensional organic semiconductors are modelled by a linear supercluster of six molecules. The general expression for the complex frequency‐dependent conductivity of the compounds composed from such superclusters is derived and the electron coupling to the totally symmetric intrameolcular modes of vibration is taken into account. Electron eigenstates and eigenvalues of the supercluster are calculated in terms of Hubbard model in the limiting case of infinite Coulomb repulsion (U → ∞). Explicit calculations of the real part of the complex conductivity predict the shift of electronic excitation band to the lower energy as the interaction between dimers or trimers increase.
Calculation of Dipole Transition Matrix Elements in Crystals by the Relativistic Green's Function Method
Authors: Shilkova N. A. , Shirokovskii V. P. 
Published: July 2007

AbstractAn analog of Green's theorem for the Dirac operator is obtained, which allows to reduce the integration over the outer part of the Wigner‐Seitz cell volume to that through the muffin‐tin sphere surface. Within the relativistic variant of the Green's function method, matrix elements of the velocity operator are computed in the veritable relativistic and c → ∞ cases. A comparison is made with the momentum matrix elements calculated by the nonrelativistic technique.
Electric Conductivity of a Metallic Ferromagnet and Magnetization Process
Authors: Zakharov Yu. V. , Mankov Yu. I. , Titov L. S. 
Published: July 2007

AbstractThe dependence of the conductivity and the magnetoresistance of a multi‐domain metallic ferromagnet on the magnetization when current flows along a domain wall is studied. The expression for the conductivity is obtained as function of x‐coordinate which is normal to the domain wall plane. It is shown that the region of current localization in a compensated ferromagnet has a size in the x‐coordinate of the order of the cyclotron radius near a single domain wall and becomes of the order of the decreasing domain width under magnetization. The magnetoresistance sharply increases in an external magnetic field near the saturation region. A comparison is made with the experimental data on the magnetoresistance of a ferromagnet with domain structure. It is shown that the appearance of nuclei of reverse‐magnetized domains leads to a resistance drop in the beginning of the magnetization process.
Influence of Electron–Magnon Interaction on Electronic and Magnetic Properties of Ferromagnetic 4f Systems
Authors: Nolting V. , Nolting W. 
Published: July 2007

AbstractA fully selfconsistent approach is proposed to the s‐f model of a ferromagnetic 4f‐system. A Green's function method is used for studying the mutual influence of itinerant conduction electrons and localized 4f‐moments. The striking temperature‐ and carrier concentration‐dependence is inspected of the conduction band structure, the electron spin polarization, and the Curie‐temperature Tc. A drastic Tc‐enhancement is observed with increasing band occupation, n, as a consequence of the s‐f exchange and the Coulomb interaction between the conduction electrons.
Thermoluminescence Study of Charge Traps in Polycrystalline Layers of Phenanthrene
Authors: Dreger Z. , Kalinowski J. , Davoli I. , Stizza S. , Feliziani S. 
Published: July 2007

AbstractUV‐induced thermoluminescence (UVTL) experiments are carried out on polycrystalline films of phenanthrene. Applying the fractional glow technique the distribution of charge traps in energy is determined. The distribution appears to be quasi‐continuous within the energy range 0.25 to 0.60 eV, peaking at two energies Et(I) = 0.27 eV and Et(II) = 0.43 eV, and showing a cutoff at its low‐ and high‐energy edges. The peaks reflect the two maxima of the UVTL glow curves and correspond to different emission centers. It is the consequence of the distance and concomitant energy distribution of geminate trapped electron–hole pairs produced at the stage of the TL excitation. The results demonstrate that the discrete trap‐model, used extensively for the polycrystalline aromatic compounds, is not applicable to phenanthrene evaporated under vacuum onto a rigid substrate.
X‐Ray Bragg Dynamical Diffraction in Crystals Weakly Deformed by Ultrasonic Waves
Authors: Polikarpov I. V. , Skadorov V. V. 
Published: July 2007

AbstractThe dynamical diffraction of X‐rays in crystals weakly deformed by transverse ultrasonic waves is investigated. Analytical expressions for the crystal reflection tensor and the modified refractive indexes for the cases of two‐and four‐level X‐ray‐acoustic resonances are obtained. It is shown that the modified refractive indexes and reflection tensor depend on the X‐ray‐acoustic resonance conditions.
Reaction of OH− and F Centers in Sodium Halides
Authors: Radzhabov E. 
Published: July 2007

AbstractThe influence of an additive coloration procedure on the absorption spectra of sodium halides doped with hydroxide is studied. The reaction of OH− and F centers leads to the creation of H and O2−‐vacancy centers in NaF, NaCl, NaBr crystals. The reaction yields H and O− centers in NaF doped with LiOH. Photodissociation of H and O− vacancy is studied, too. The possibility of the reaction of F and OH− centers in alkali halides is estimated on the base of the effectiveness of the reaction of free alkali metals with metal hydroxides. The reaction in alkali halides doped with LiOH is observed, too.
Atomic Diffusion in Tetrahedral Semiconductors. Approximative Treatment of Diffusion Theories
Authors: Enders P. , Schade U. 
Published: July 2007

AbstractThe transport of dopants in semiconductors can often be described within an interstitial–substitutional or diffusion‐reaction mechanism, e.g. for Zn in GaAs and in InP. The interpretation of experimental data, e.g. SIMS profiles, is largely complicated by that a nonlinear diffusion equation with several not precisely known coefficients has to be solved. In order to circumvent the parameter fit via the numerical solution of such a differential equation, approximately it is solved by means of the integral balance method. The usefullness of this approach is demonstrated by comparison with experimental and numerical results.
Application of the Local Environment Model to the Thermodynamics of Large Hard Core Interstitial Solutes in Binary Alloys
Authors: Oates W. A. , Mika K. 
Published: July 2007

AbstractThe local environment or cell model for interstitial solutes in binary alloy solvents is extended to those cases where the short range solute‐solute repulsive interactions effectively exclude or block sites adjacent to already occupied sites. The host alloy is assumed to be random and correlations between the locations of interstitial sites, which occur even in this case, are also allowed for. It is found that blocking and site correlation have a significant effect on the variation of the partial molar energy and entropy of the solute with concentration.
On the Scattering of Electrons by Confined LO Phonons in a Semiconductor Quantum Well
Authors: Leon H. , Comas F. 
Published: July 2007

AbstractScattering and momentum‐relaxation rates are calculated for a semiconductor quantum well (QW) considering electron scattering by confined LO phonons. Electron coupling with confined LO phonons is treated on the basis of an interaction Hamiltonian deduced in a previous work, while both electrons and LO phonons are assumed to be completely confined to the QW active layer. Besides the exact results, results are reported in the so‐called momentum‐conservation approximation (MCA) and the fractional error implied in the MCA is calculated. Detailed comparison with previous works (in the non‐confined phonon case) is made.
Surface Plasmons in Type II Superlattices
Authors: Sy H. K. , Song L. M. 
Published: July 2007

AbstractA semi‐infinite type II semiconductor superlattice is studied using coupled Boltzmann equations. The exact equation is obtained for the surface plasma modes when the dielectric media inside and outside the surface are different. The number of solutions which are free from Landau damping depends on the parameters used.
Theory of Inelastic Low‐Energy Electron Scattering with Generation of Surface and Bulk Excitons in Molecular Crystals
Authors: Strelniker Ya. M. 
Published: July 2007

AbstractThe inelastic scattering of electrons on the surface of a semi‐infinite crystal with creation of surface and bulk molecular excitons is considered. Analytical expressions are obtained for the cross‐section of inelastic scattered electrons. The angular and energy dependences of cross‐section are investigated. A strong peak of the electron scattering is noted to be due to definite value of the wave vector of bulk exciton. The possibility to investigate the exciton band structure is discussed.
Light Quenching of Photoconductivity in Indium‐Doped Lead Tin Telluride
Authors: Möllmann K.‐P. 
Published: July 2007

AbstractIn strongly indium doped lead tin telluride (x > 0.2) at temperatures T < 30 K with interband excitation (hv > 3Eg) a “negative” photoconductivity is observed. This effect is attributed to quenching of the photoconductivity caused by background photon flux. The quenching of photoconductivity is discussed in terms of excitation into Jahn‐Teller centres in the conduction band at hv > 3Eg.
Comments on the EPR Spectrum of Tetravalent Chromium in Ruby
Authors: Marshall S. A. , Yu C. , Zhang Y. N. 
Published: July 2007

AbstractThe electron paramagnetic resonance absorption spectrum of tetravalent chromium in ruby is re‐examined at X‐band wavelengths. Spectral parameters are provided from data obtained at 4.2 K. Among these, the strength of the orthorhombic component to the crystalline electric field is given along with a suggestion of its associated direction.
Colour Centres in Alkali Metal Doped CaF2
Authors: Hamaïdia A. , Hachimi A. 
Published: July 2007

AbstractUsing optical spectroscopy and magnetic circular dichroism (MCD) colour centres are studied in CaF2:Li+ and CaF2:Na+. In each of these two matrices, there exists a weakly perturbed FA centre which is called F and probably a more deeply perturbed FA centre or F; the centre which is improperly named F2A has a paramagnetic ground state, its MCD is very different from that of the F2 centre in pure CaF2; there are two non‐paramagnetic centres “F3A+” and f with similar optical and magneto‐optical properties but with a long wavelengths shift of the absorption and emission spectra of the f centre.
CoK X‐Ray Absorption Near‐Edge Structure of Cobalt(III) Complex Compounds
Authors: Kitamura M. , Sugiura C. , Muramatsu S. 
Published: July 2007

AbstractExperimental and theoretical studies of the CoK X‐ray‐absorption spectra for [Co(NH3)6]Cl3, [Co(NH3)5Cl]Cl2, trans‐ and cis‐[Co(NH3)4Cl2]Cl complexes are reported. The theoretical investigation is based on a multiple‐scattering theory. Overall profiles of the observed spectra are generally predicted by multiple‐scattering calculations for a single complex. Polarized spectra are presented to show that they are closely related to an arrangement of atoms along the direction of the polarization of the exciting X‐ray.
Coherent Compton Effect under Conditions of X‐Ray Dynamical Laue Diffraction
Authors: Bushuev V. A. , Kazimirov A. Yu. , Kovalchuk M. V. 
Published: July 2007

AbstractA new scheme of the investigation of the coherent Compton scattering (CS), which consists in registration of the CS under conditions of the X‐ray dynamical Laue diffraction is realised. The general features of the angular dependence of the CS intensity MoKα‐radiation from the exit surface of perfect silicon crystals under the (111) reflection are investigated. The contribution of the silicon valence electrons to the atomic factor of the X‐ray scattering is experimentally determined.
Reactions for Iron Centers in Silicon under Optical Pumping
Authors: Bagraev N. T. , Polovtsev I. S. 
Published: July 2007

AbstractUsing the photoconductivity, EPR, and optical nuclear polarization (ONP) techniques, lightstimulated reactions leading to the rearrangement of defects in silicon doped with iron are investigated. The observed quenching and regeneration of Fe0 centers are explained on the basis of a concept suggesting the existence of a local negative‐U energy for defects with deep levels in semiconductors.
Anisotropy of the Mössbauer Effect in ß‐Sn under Pressure and the Lattice Dynamics
Authors: Opalenko A. A. , Kornilova A. A. 
Published: July 2007

AbstractThe Mössbauer effect probability is measured in single crystal tin samples oriented in the (100) and (001) planes under hydrostatic pressure up to 40 × 108 Pa. It is found that the anisotropy of the probability f001/f100 changes from 0.65 ± 0.02 at P = 0 to 0.90 ± 0.02 at P = 40 × 108 Pa. The experimental data for single crystals and polycrystals of tin under pressure are theoretically explained using the Brovman‐Kagan model of lattice dynamics.
Low‐Temperature Heat Capacity and Phonon Spectra of 4,4′‐Difluorobiphenyl
Authors: Wąsicki J. , Gurevich A. M. , Eropkin V. N. , Mayer J. , Natkaniec I. , Telezhenko Yu. V. , Khomenko V. G. 
Published: July 2007

AbstractHeat capacity, inelastic incoherent neutron scattering and neutron diffraction experiments are performed for 4,4′‐difluorobiphenyl. The heat capacity is measured between 4.2 and 100 K using the adiabatic calorimetry technique. An interpretation of the temperature dependence of the heat capacity in terms of spectral characteristic is given. The results are finally compared with those of the isostructural crystalline biphenyl.
Effective Scattering Times of Inversion Electrons in InSb Grain Boundaries Deduced from Cyclotron Resonance Measurements
Authors: Ludwig F. , Müller H.‐U. , Herrmann R. 
Published: July 2007

AbstractThe effective scattering times of inversion electrons in InSb grain boundaries are investigated by means of cyclotron resonance measurements in the submillimeter wavelength range between λ = 118.8 and 513 μm. It is found that the inversion electrons in the InSb grain boundary have essentially higher scattering times than estimated from the onsets of Shubnikov‐de Haas oscillation periods. Furthermore, it is shown that the scattering times decrease with increasing magnetic field in qualitativ agreement with the theoretical result for the limit of a short‐ranged scattering potential. The scattering behaviour is discussed in the framework of this model.
Electronic and Structural Properties of Tungsten Bronzes
Authors: Bonnet A. , Conan A. , Morsli M. , Ganne M. , Tournoux M. 
Published: July 2007

AbstractTransport coefficient measurements (electrical conductivity and thermoelectric power) are performed on compact bars of antimony and bismuth tungsten bronzes in polycrystalline form over the temperature range 100 to 500 K. Experimental results are discussed in comparison with those obtained recently on antimony and bismuth molybdenum bronzes in which two inverted narrow levels pin the Fermi level near the midgap. A single band model accounts for all the experimental results. In Bi4W20O62 the conduction mechanisms are governed by hopping in states near the Fermi energy. It is shown that variable range hopping occurs at low temperature whereas next neighbour hopping takes place at higher temperature. This band may be formed by the overlap of some broadened levels. The antimony phases are characterized by a non‐activated electrical conductivity and small TEP. These results are interpreted under the assumption that this narrow band broadens: this wide band is less than half‐filled and the electronic states are highly delocalized leading to “metallic” behaviour.
ESR Study of Mo3+ Containing Mixed Yttrium–Scandium–Aluminium Garnet Single Crystals
Authors: Asatryan H. R. 
Published: July 2007

AbstractESR of Mo3+ ions in mixed single crystals of yttrium–scandium–aluminium garnets Y3Al2−xScx. Al3O12, where 0 ≦ x ≦ 2 is investigated. Several new centers of Mo3+ differing from those for Y3Al5O12 single crystals are observed due to changes of symmetry and crystal field parameters associated with isomorphous substitution of octahedrally coordinated Al3+ (a) by those of Sc3+ in the third coordination sphere. Symmetry, nearest coordination, and spin–Hamiltonian parameters are estimated concerning with all Mo3+ centers in Y3Al2−xScxAl3O12 crystals for x < 0.15. It is found that in Y3Sc2Al3O12 (x = 2) the Sc3+ ions substitute also Y3+ at dodecahedral sites.
The Critical Temperature of the Axial Next‐Nearest‐Neighbour Ising Thin Film
Authors: Duda A. 
Published: July 2007

AbstractThe critical temperature of the disordered to ordered phase transition is calculated for the axial next‐nearest‐neighbour Ising thin film within the molecular‐field approximation. The effects originated in the finite size of the sample and the surface perturbation of the exchange coupling are discussed. It is found that for appropriate values of the surface parameter, the critical temperature can exceed the value corresponding to the infinite, ideal crystal.
On the Coercivity of Texturized Uniaxial Permanent Magnets
Authors: Elk K. , Jahn L. 
Published: July 2007

AbstractTo study the texture dependence of the coercivity of polycrystalline materials a model is considered taking into account coherent rotational processes and Bloch wall jumps simultaneously but neglecting a magnetic coupling between the identical grains. The texture is described by an one‐parametric distribution function. Using this model the magnetization coercivity Hc and the remanence coercivity HR are calculated. Especially the upper limits of Hc and HR are investigated. It follows that for technically attainable degrees of alignment (characterized by MR ≦ 0.98MS) a maximum value of Hc ≈ 0.677 HA cannot be exceeded.