bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Plasma Minimum in Semiconductors with Anisotropic Energy Bands
Authors: Zukotynski S. , Saleh N. 
Published: July 2007

AbstractSemiconductors with ellipsoidal and non‐parabolic energy bands are considered. A relaxation time of tensor character is assumed. The solution of the transport equation obtained by Zukotynski and Grynberg [1], is generalized to include a time‐dependent electric field. The results are then used in the Maxwell equations and the condition of minimum reflection is obtained. Both the Faraday and Voigt configurations in a small magnetic field are considered. The position of the plasma minimum is found to depend on the state of polarization of the incident radiation with respect to the energy surfaces.
Anomalous X‐Ray Absorption and Photocurrent in CdS Single Crystals (Symmetrical Laue Case)
Authors: Brümmer O. , Stephanik H. 
Published: July 2007

AbstractIt is shown that the photocurrent in CdS single crystals can be used for detecting the existence of wavefields in crystals as well as a method for proving the X‐ray‐intensity distribution in the regions of the individual atoms. The investigation was carried out by means of a double‐crystal spectrometer in (2, −2) position under the application of MoKα and CuKα radiation. Agreement between theoretical calculation and experimental results has been found.
Dielectric Properties of KCl, KBr, and KI Single Crystals in the Extreme Ultraviolet up to 35 eV
Authors: Blechschmidt D. , Klucker R. , Skibowski M. 
Published: July 2007

AbstractThe reflectance of freshly cleaved single crystals of KCl, KBr, and KI has been measured for 15° angle of incidence at room temperature for photon energies between 5 and 35 eV, using the continuous spectrum of synchrotron radiation. For photon energies from 12 to 30 eV the optical constants, the dielectric constant, and the energy loss function were determined by reflectance measurements with parallel polarized light at several angles of incidence between 15° and 75°. A prominent doublet near 20 eV is found for all potassium halides. It is assigned to excitonic transitions from the K+3p core level to the conduction band at Γ and X. Energy differences between some critical points at Γ and X are estimated by comparing the position of the fundamental doublet and the K+3p doublet.
Piezotransport and Piezoabsorption of Tellurium‐Intrinsic Effects
Authors: Herrmann K. H. , Ochel M. , Puhlmann J. 
Published: July 2007

AbstractDynamic piezo‐Hall effect and piezoabsorption of tellurium single crystals have been measured. The results are compared with dynamic piezoresistance reported previously. General features are outlined for intrinsic piezotransport and intrinsic piezoabsorption of a material showing an exponential absorption edge. The measurements are evaluated with respect to band structure parameters and pressure derivatives of the gap.
Absorption Spectrum and Zeeman Effect of Ho3+ in YPO4
Authors: Becker P.‐J. , Kahle H. G. , Kuse D. 
Published: July 2007

AbstractThe optical absorption spectra of trivalent holmium in single crystals of HoPO4 and (Y, Ho)PO4 have been measured in the range from 15000 to 29000 cm−1 including the Zeeman effect of the ground level 5I′8 and the two excited levels 3K′8 and 5G′5 at 85 and 4.2 °K. The splitting factors of the degenerate components of the ground level and the level 3K′8 indicate a small mixing of the states ΨγJ M with different M. With this fact some special features of the transitions between these two levels can be explained qualitatively.
F‐, FA‐ and Z1‐Center Calculations Using Approximate Pseudopotentials
Authors: Weber W. , Dick B. G. 
Published: July 2007

AbstractThe authors carried out variational calculations on F‐, FA‐, and Z1‐centers, using a technique which was proposed by Bartram, Stoneham, and Gash. To illustrate how the method works, ionization potentials of alkali atoms are calculated for different trial wave functions. Plausible criteria are used to limit the choice of wave functions in a manner which avoids the necessity of using experimentally determined parameters. The agreement with F‐, FA‐, and Z1‐data is good. For the Z1‐center, the experimentally favored so‐called model I is given further theoretical support. Moreover, there is found evidence for a possible displacement of the divalent cation impurity of the Z1‐complex.
The Spin‐Wave Dispersion Relations and the Spin‐Wave Contribution to the Specific Heat of Antiferromagnetic UO2
Authors: Cracknell A. P. , Joshua S. J. 
Published: July 2007

AbstractWe have used the recently measured spin‐wave dispersion relations of antiferromagnetic UO2 to calculate the spin‐wave contribution to the specific heat of this material as a function of temperature below 20 °K. The symmetries of the spin‐wave dispersion relations are also discussed.
Nonlinear Optical Effects in a System with Degenerate or Closely Spaced Levels in Solids
Authors: Kovarskii V. A. , Perlin E. Yu. 
Published: July 2007

AbstractThe influence of two external high‐frequency electric fields (one of them being the field of strong laser beam) on a three‐level system with doubly degenerated excited states is considered. The change of the refractive index and of the ground‐frequency light‐absorption coefficient in the presence of laser radiation are predicted.
The Elastic Behaviour of NiCo Alloys
Authors: Leamy H. J. , Warlimont H. 
Published: July 2007

AbstractThe adiabatic, elastic stiffnesses of five f.c.c. Ni—Co alloys in the range from 10 to 62% Co were determined by the ultrasonic pulse‐echo technique at temperatures between 77 and 300 °K. As Co is added to Ni the bulk modulus increases linearly while (C11 − C12)/2 and C44 decrease and increase, respectively. The alloy stiffnesses were extrapolated to 100% Co to yield the following estimates for the stiffnesses of f.c.c. Co at room temperature: B = 1.89, (C11 − C12)/2 = 0.38, C44 = 1.33 (dynes/cm2 × 1012). Debye temperatures calculated from the extrapolated 0 °K stiffnesses indicate that the high temperature instability of h.c.p. Co is due to the more favorable vibrational entropy of f.c.c. structure.
Commutation Effect in Bismuth Type Semimetals
Authors: Bivol V. G. , Bodiul P. P. , Fedorko A. S. , Gitsu D. V. 
Published: July 2007

AbstractThe dependence of the Nernst‐Ettingshausen longitudinal effect on the direction of the magnetic field for the case of semimetals is studied theoretically and experimentally. A quite unique correspondence is found between the anisotropy of the effect and the band structure near the Fermi level. It is shown that the commutation effect which determines the dependence of the magneto‐thermo‐e.m.f. magnitude on the direction of the induction vector, permits to judge about the number and localization of band extrema in the k‐space. This is an effective way for studying band structures of bismuth and its alloys at high temperatures.
On Sensitizing Recombination Centres in GaSe Single Crystals
Authors: Abdullaev G. B. , Kh. Alieva M. , Belenkii G. L. , Mamedova A. Z. 
Published: July 2007

AbstractAn investigation is made of the stationary photoconductivity and its kinetic, the thermally stimulated conductivity, and the mobility of current carriers of tin‐doped p‐GaSe single crystals. It is shown experimentally that the recombination in such crystals is controlled by two types of recombination centres: one of them being “slow” (r), another “fast” (s). The principal parameters of “slow” recombination centres (r), thermal (E = 0.58 eV) and optical (E = 0.78 eV) energetic depth from C‐band, electron (Sn r = 5 × 10−14 cm2) and hole (Sp r = 3 × 10−20 cm2) capture cross‐sections, are measured. The concentration is found to be equal to Nr = 3 × 1014 cm−3. It is shown that the r‐centre is a single charged donor which may be due to substituting Ga atoms by Sn atoms in the GaSe lattice.
Galvanomagnetic Effects in Tellurium in Magnetic Fields up to 160 kG at Temperatures between 150 and 350 °K
Authors: Zimmermann W. 
Published: July 2007

AbstractAll components of the Hall effect and the magnetoresistance were measured in magnetic fields up to 160 kG at temperatures between 150 and 350 °K. The experimental results are interpreted by a six‐ellipsoid model for the valence band maxima. The ellipsoids are centered on the mirror planes of the reciprocal lattice. It is assumed that the collision time depends on energy only and that scattering takes place mainly on acoustical phonons. Only four of the twelve measured values are used to determine free parameters, the others to test the model. The hole mobilities perpendicular to the direction of the c‐axis and parallel to it are at 200 °K μ⟂ = 926 cm2 V−1s−1 and μ⟂ = 1755 cm2 V−1s−1. Results in the intrinsic range are reported.
Analysis of Defect Annealing in Monocrystalline Gold Foils after Gold Ion Irradiation
Authors: Wittmaack K. 
Published: July 2007

AbstractMonocrystalline gold foils were irradiated at −196 °C with gold ions parallel to [101] or at random incidence. Defect production and subsequent isochronal recovery between −180 and 40 °C were examined by means of the electrical resistance for energies from 5 to 30 keV and doses from 5 × 1012 to 5 × 1015 ions/cm2. The annealing spectra are characterized by an intense dose‐dependent peak between −40 and −25 °C which is interpreted as being due to the recombination of freely migrating interstitials (E = (0.77 ± 0.07) eV) with vacancies. After high‐dose preirradiation and subsequent annealing the recovery in the dominant peak is reduced in favour of a new peak appearing between 0 and 40 °C. This is explained in terms of a migration of vacancies to defect clusters.
Sur le modèle de l'électron collectif de Stoner
Authors: Munschy G. 
Published: July 2007

AbstractDans l'approximation de Hartree‐Fock, il s'ajoute à la somme des énergies à une particule une énergie d'interaction électrostatique qui leur reste irréductible. En attribuant à celle‐ci la signification d'une moyenne statistique dans le cadre du modèle de ferromagnétisme de l'électron collectif, l'auteur aboutit à une condition d'équilibre statistique différente de celle de Stoner. Elle permet d'expliquer pourquoi les courbes d'aimantation calculées décroissaient trop vite et laisse prévoir aussi un comportement plus correct de la chaleur spécifique au voisinage du point de Curie.
Acoustoelectric Phenomena in Piezoelectric Semiconductors
Authors: Quentin G. , Thuillier J. M. 
Published: July 2007

AbstractCurrent saturation and growth of stationary domains of high electric field are observed for many piezoelectric semiconductors. It is shown that such phenomena may be explained when a constant‐current pulse is applied to the sample. To study the steady state we include in the dc current the acoustoelectric term. With some simplifying assumptions, a simple theoretical calculation of the current—voltage characteristic and of the electric field repartition is given. A comparison is made with experimental results.
Ferroelectric and Antiferroelectric Symmetry Groups
Authors: Schelkens R. 
Published: July 2007

AbstractThe theory of the color or Shubnikov groups can be used to work out a difference between those groups associated with antiferroelectric and those associated with ferroelectric structures. A comparison with the magnetic symmetry groups shows that a symmetry group for a ferroelectric structure is, in general, different from a symmetry group for a ferromagnetic structure, having the same point group. These general results are applied to the study of a ferroelectric crystal, and, in particular the substance barium titanate.
Electronic Properties of Tetracyanoquinodimethane (TCNQ) Salts: Hall Effect in Crystals of the Triethylammonium (TCNQ)2 Complex
Authors: Farges J.‐p. , Brau A. , Vasilescu D. , Dupuis P. , Néel J. 
Published: July 2007

AbstractA report is given of a successful measurement of the Hall effect in single crystals of the organic salt triethylammonium (TCNQ)2 at room temperature. A Hall mobility of the order of 0.6 cm2/Vs was found, the sign of the Hall constant being that appropriate for hole carriers. A study of the thermoelectric power sign was in agreement with the existence of holes. Study of the temperature dependence of the conductance indicated that some electrically active, gaseous impurities, which were believed to act as acceptors, were present in the samples. An interpretation of the experimental results is presented, including a discussion of the effect of the impurities on the electronic properties of the material. Some indications about the conduction process are suggested on the basis of a two‐band model.
Dislocation Structures in Fatigued CuZn Single Crystals
Authors: Lukáš P. , Klesnil M. 
Published: July 2007

AbstractDislocation structures in CuZn alloy single crystals were examined by means of transmission electron microscopy. The overall dislocation structure, typical for the whole volume of fatigued crystals, strongly depends on the degree of difficulty of cross slip. In crystals with sufficiently easy cross slip the surface extrusions and intrusions were found to be related to the persistent slip band structure, differing from that in the remaining volume, while in crystals with very difficult cross slip no persistent slip bands lying under the surface relief were found. Further, the role of the persistent slip bands in fatigue process is discussed.
Antiferromagnetism of Zn0.87Mn0.13Fe2O4
Authors: Fayek M. K. , Leciejewicz J. , Murasik A. , Yamzin I. I. 
Published: July 2007

AbstractThe magnetic structure of Zn0.87Mn0.13Fe2O4 polycrystalline samples has been studied by neutron diffraction at 4.2 °K. The indices of the magnetic peaks observed are hkl/2 with l and h + k odd only, where hkl are the indices for the spinel‐type unit cell. The absence of magnetic contributions in the reflections with even l indicates the antiferromagnetic type of ordering. The appearance of a liquid‐type diffuse peak under the strong magnetic reflections (10 1/2) suggests that the long‐range magnetic order both in the A and B sites is still not complete at 4.2 °K. In the proposed model the long‐range magnetic ordering in the A sublattice has been neglected. The magnetic ordering inthe B sites can be described in terms of four sublattices, 1, 2, 3, 4, each containing the positions: x, y, z; XY, z; Y, x, 1/2 — z; y, X, 1/2 — z; +(0, 0, 0); (1/2, 1/2, 1/2) where x, y, z are: 1/8, 1/8, 5/16; 1/8, 1/8, 13/16; 1/8, 5/8, 9/16; 1/8, 5/8, 1/16. The sublattice 1, 2 (and 3, 4) have opposite spin alignment. The angle between 1, 3 (and 2, 4) lattices could not be determined from the powder neutron data. The value of the magnetic moment for Fe3+ was determined to be (3.0 ± 0.1) μB. The magnetic transition temperature was found to occur at (11.0 ± 0.5) °K.
On the Monomolecular Recombination Luminescence and Its “Blowing‐up” by the Electric Field
Authors: Antonov‐Romanovskii V. V. 
Published: July 2007

AbstractOn the basis of the diffusional theory of luminescence the fraction of the monomolecular luminescence and the effect of not very strong electric fields on recombination processes in uniformly excited phosphors are estimated taking into account the smallness of the free carrier mean path. The fraction of the luminescence of short duration caused by a recombination before the localization and that one of long duration caused by the recombination after localization are also estimated. A formula which determines the probability of the recombination of electron‐hole pair components is derived. Some calculations for alkali halide phosphors are carried out.
Electron Emission Spectra of Alkaline Earth Fluorides
Authors: Petrescu P. , Giurgea M. 
Published: July 2007

AbstractThe photostimulated electron emission spectra of CaF2, SrF2, and BaF2 crystals, coloured by electron bombardment, are analysed. The comparison with optical absorption spectra leads to some conclusions with respect to the kind of colour centres corresponding to the various bands observed. The results verify a relation of the Mollwo‐Ivey type. Some complex bands are resolved.
Jahn‐Teller Effect and Partially Covalent Bond as Causes of Low Symmetry of Ga+, In+, and Tl+ Centres in CsCl‐Type Alkali Halides
Authors: Zazubovich S. G. 
Published: July 2007

AbstractPartially polarized luminescence is observed for Ga+, In+, and Tl+ centres in alkali halides of CsCl‐type structure at liquid nitrogen temperature. The symmetry of excited Ga+, In+, and Tl+ centres is established to be tetragonal in the most crystals investigated. The symmetry of Tl+ centres in CsI:Tl crystals is trigonal. The possible causes of the low symmetry are discussed. The interaction of the optical electrons of the activator with tetragonal vibrations of the lattice may be the main cause for the low symmetry of the excited Ga+, In+, and Tl+ centres in most of the alkali halides. The partial covalent bond between thallium and some of the surrounding iodine ions seems to be essential for CsI:Tl crystals.
Calculation of Structure Constants Needed in the Kohn‐Korringa‐Rostoker Method for Lattices with N Atoms per Unit Cell
Authors: Lehmann G. 
Published: July 2007

AbstractA new technique is suggested for the calculation of structure constants used in the KKR method for lattices with N atoms (N > 1) per unit cell. This new method has the advantage that the coefficients B, must not be calculated separately for every pair i j of atoms and for every special position of these atoms in the unit cell. It has the disadvantage that the structure constants DL necessary for the calculation of B, must be known for higher values of angular momentum L than in the usual approach. But an estimate shows the superiority of the proposed method for greater numbers N of atoms.
Étude de la perméabilité de l'eutectique supraconducteur CdSn à structure lamellaire
Authors: Dobrosavljevic L. , Petipas‐Dupuis C. , Racek R. 
Published: July 2007

AbstractNous avons étudié la perméabilité superficielle R.F. de l'eutectique Cd–Sn à structure lamellaire SNSN … pour des températures inférieures à la température critique du système (TCNS ≈ 3,6 °K). Le champ magnétique H est toujours dans le plan des lames et l'épaisseur des lames normales N(Cd) est grande par rapport à la longueur de cohérence. On interpréte les résultats en terme d'une pénétration (dans chaque lame de cadmium) d'un réseau unidimensionnel de vortex, pour des champs supérieurs à une certaine valeur Hc 1 (faible).
The Anisotropy of the Thermoelectric Power in the (100) Plane of As‐ and P‐TCNQ Single Crystals
Authors: Zosel D. , Ritschel H. , Hänsel H. 
Published: July 2007

AbstractSingle crystals of triphenylmethylarsonium 7, 7, 8, 8‐tetracyanoquinodimethane (As‐TCNQ) and triphenylmethylphosphonium 7, 7, 8, 8‐tetracyanoquinodimethane (P‐TCNQ) show an important anisotropy of the thermoelectric power. The anisotropy of the thermoelectric power in the (100) plane has been measured in the temperature range of about 200 to 400 °K using a special 13‐probe thermoelectric power measuring cell. The direction dependence of the thermo‐e.m.f. in the (100) plane is described by ΔU = (φ1 cos2 ψ + + φ2 sin2 ψ) ΔT, although not all of the underlying assumptions for this relation are satisfied in the whole temperature range. The measured shapes of the curves are considerably influenced by crystal defects.
Numerical Analysis of Properties of Dislocations in Anisotropic Media within the Range of Linear Elasticity
Authors: Malén K. 
Published: July 2007

AbstractThe analysis of a curved dislocation in an anisotropic medium must be done numerically. The fields can be expressed in various line integral forms. In the analysis used in this paper the basic data are derived from data for straight dislocations. For comparison some other line integral expressions are given. The explicit expressions for the roots to the sextic equation in terms of hypergeometric functions do not seem to have advantages over a direct iterative solution of the equation. The angular derivatives of field quantities for straight dislocations can be found using the transformation properties of the elastic constants. A simple example is given of the use of an integration over angle using data for straight dislocations to estimate the force on a dislocation.
Relaxation von Fehlstellendipolen in AgCl‐Kristallen II. Ergebnisse an AgCl:Ti3+, AgCl:V3+ und AgCl:Cr3+
Authors: Kunze I. , Müller P. 
Published: July 2007

AbstractDie in AgCl‐Kristallen aus dreiwertigen Fremdkationen und zwei Leerstellen gebildeten Komplexe wurden mit Hilfe von ITC (ionic thermo‐current)‐Messungen untersucht. AgCl:Cr3+ lieferte dabei ein Signal mit zwei getrennten Maxima. In AgCl:V3+ wurde ein komplizierteres Signal gemessen, das aus drei sich überlagernden Maxima besteht, während in AgCl:Ti3+ nur ein einfaches ITC‐Maximum auftrat. Diese Signale unterschieden sich vollständig von den früher in AgCl:Cr2+ und AgCl:V2+ gefundenen. Zur Diskussion der Ergebnisse wurde die Zahl der elektrisch aktiven Relaxationsmodi für verschiedene Fälle der Verteilung der beiden Leerstellen auf die nächsten und übernächsten Nachbarplätze des Fremdkations berechnet.
Das Spinwellenspektrum von Eisen–Aluminium‐Legierungen in der Nähe des stöchiometrischen Verhältnisses 3:1
Authors: Elk K. 
Published: July 2007

AbstractIn der Nähe des stöchiometrischen Verhältnisses 3:1 existieren drei Phasen, die sich durch ihre Atomanordnung unterscheiden. Die zugehörigen Spinwellenspektren werden berechnet, wobei für die beiden ungeordneten Phasen ein Variationsverfahren benutzt wird. Die Spektren ergeben sich als deutlich voneinander verschieden, insbesondere entstehen drei stark verschiedene Steifigkeits‐Konstanten.
The Effect of a Short‐Range Three‐Body Potential on the Properties of Inert Gas Solids
Authors: Roy D. , Basu A. N. 
Published: July 2007

AbstractA short‐range three‐body interaction which arises from the deformability of the charge cloud of an atom is included in the interaction between atoms of an inert gas solid and its effect on the dispersion curves and elastic constants is discussed. The result is applied to krypton. Experimental dispersion curves, the bulk modulus at absolute zero, and the Debye temperature are compared with calculated values. It is found that on the whole the inclusion of the three‐body potential improves the agreement.
Optical Properties of Na and Li Halide Crystals at 55 °K
Authors: Baldini G. , Bosacchi B. 
Published: July 2007

AbstractNew results on the low temperature reflectivity of Li and Na halides between 5 and 10 eV are reported and discussed on the basis of recent band structure calculations. Furthermore, fine structure accompanying the lowest exciton has been detected in some crystals. This structure is examined in detail and attributed to the exciton‐phonon interaction.
On Bonding and Structure of Epitaxial Bicrystals I. Semi‐Infinite Crystals
Authors: Ball C. A. B. , van der Merwe J. H. 
Published: July 2007

AbstractThe bonding in epitaxial bicrystals and its influence on their structural properties, assumed to be governed by lowest energy configurations, are considered. The Peierls‐Nabarro model for the interfacial interaction between two semi‐infinite crystals, used previously, is extended in Part I to include the second term in a Fourier series. This is believed to represent the true interaction more closely. Three approximate expressions for the energy are obtained, one of which is in the form of a useful analytical expression. In Part II the considerations are extended to thin films.
Conductivity of Hot Holes in Silicon at 77 °K
Authors: Asche M. , von Borzeszkowski J. , Sarbei O. G. 
Published: July 2007

AbstractThe conductivity of holes in p‐Si is measured as a function of electric field strength in the 〈100〉, 〈110〉, and 〈111〉 directions of crystals with different resistivities (6000 Ω cm ≧ ≧ Q300 °K ≧ 0.45 Ω cm) at 77 °K. The values obtained for samples from highly purified crystals are compared with the heavy hole mobility calculated theoretically within the framework of the same model which allowed to explain the dependence of mobility on lattice temperature. The different influence of the interaction with optical phonons on both the effects is caused by the non‐parabolic band structure, reflected more strongly by the field dependence of the mobility.