bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Describing a Flexible Dislocation
Authors: Bacon D. J. 
Published: July 2007

AbstractA procedure for determining the equilibrium shape of a dislocation under the influence of both internal and external stress fields is described. The method, which is an extension of that used by Brown to determine the shape of extended nodes, does not require the explicit numerical integration of line integrals to obtain the self‐stress, and line shapes are therefore computed with comparative simplicity. The procedure has been used to study the bowing characteristics and the critical shapes and stresses of Frank‐Read sources of various lengths and orientations, and the results are compared with those of the line tension model. The effects on the critical features of an orientation‐dependent friction stress have also been studied. Similar results on the bowing characteristics of a dissociated dislocation in the f.c.c. structure and their dependence on stacking fault energy are also presented.
Thermally Activated Deformation of Potassium
Authors: Bernstein I. M. , Li J. C. M. 
Published: July 2007

AbstractThe thermally activated deformation of single crystal and polycrystalline potassium is examined. It is shown that the activation parameters describing low‐temperature deformation can be correlated reasonably well with the b.c.c. transition metals on the basis of their respective shear moduli. This supports the suggestion that the same general mechanism controls low‐temperature deformation for all b.c.c. materials. The possibility of this mechanism being either impurity or lattice controlled is examined and it is shown that the Peierls‐Nabarro lattice resistance model adequately explains the experimental behavior. The possible role of impurities at low temperatures is briefly considered.
A Pseudopotential Approach to the Electron Band Structure of Tellurium
Authors: Picard M. , Hulin M. 
Published: July 2007

AbstractA semi‐empirical pseudopotential, derived from a study of the lead salts PbS, PbSe, PbTe, is used to compute some features of the band structure of Se and Te. For Te, this calculation confirmes previous results as the location of the band extrema. The effects of spin‐orbit coupling near the band extrema are evaluated and this yields a satisfactory picture of the main features of the band structure.
Contribution to the Determination of Gold Centre Cross Sections in Single‐Crystal Germanium by Double Injection Experiments
Authors: Hennig H.‐P. 
Published: July 2007

AbstractThe negative resistance region in Au‐doped double injection Ge diodes is investigated at 77 °K. The observed relaxation oscillations are typical of the 0.15 eV and 0.2 eV levels of gold in germanium. The time constants for the filling and emptying of the traps are determined from the mode of oscillation. The cross sections of the traps are then found by using concentration parameters derived from Hall effect measurements. These values of the cross sections agree with data available from the literature.
The Orientation Dependence of the Spin Wave Damping in Ferromagnetic Insulators with Spinel‐Structure
Authors: Voigt F. 
Published: July 2007

AbstractMeasurements are made of the relaxation frequencies of magnons at the minimum of the butterfly curve in parallel‐pumping experiments for some single crystals of ferrites and also for lithium ferrite. It is found that the anisotropic contribution to the relaxation frequency contains a large term of the sixth degree in the direction cosines of the magnetization with respect to the crystal axes. Callen and Pittelli have calculated the anisotropic ferromagnetic resonance line width in ferrites arising from the random variation of the intra‐atomic spin‐spin and spin‐orbit coupling parameters of the disordered ions. Their theory predicts a larger line width in the disordered state with a maximum in the [111] direction. The anisotropic contribution to the line width only contains a term of the fourth degree.
Photoconductivity in Amorphous Germanium
Authors: Grigorovici R. , Croitoru N. , Dévényi A. 
Published: July 2007

AbstractThe spectral dependence of the photosensitivity of amorphous germanium (a‐Ge) layers is measured at 106 °K and room temperature. The experimental data are correlated with those obtained from the optical absorption of a‐Ge. The high values and the temperature dependence of the time constant are attributed to the presence of a high density of trapping centres within the energy gap of a‐Ge.
Elektronenspin‐Resonanz von Triplett‐Exzitonen in Anthrazen
Authors: Haarer D. , Schmid D. , Wolf H. C. 
Published: July 2007

AbstractWir berichten über die Beobachtung zweier metastabiler ESR‐Linien in optisch angeregten Anthrazen‐Kristallen bei Zimmertemperatur. Die Linien wurden mit einem hochempfindlichen K‐Band‐Spektrometer (24 GHz) nachgewiesen. Durch Verwendung von moduliertem Anregungslicht (80 Hz) wurde eine Effektmodulation erzielt. Die Winkelabhängigkeit der ESR‐Linien kann mit Hilfe des von Sternlicht und McConnell angegebenen Spin‐Hamiltonoperators für Triplett‐Exzitonen analysiert werden. Die kristallographische b‐Achse ist eine der Hauptachsen des Feinstrukturtensors. Die Meßwerte für die Feinstrukturkonstanten sind D* = −(0,0058 ± 0,0015) cm−1 und E* = (0,0327 ± 0,0020) cm−1. Damit kann man die Feinstrukturkonstanten isolierter Anthrazen‐Moleküle berechnen: D = (0,0688 ± 0,0040) cm−1, E = −(0,0081 ± 0,0020) cm−1. Auf Grund der Zahlenwerte von D und E, der Zahl der ESR‐Linien und ihrer Winkelabhängigkeit schließen wir, daß es sich um ESR‐Spektren von Triplett‐Exzitonen handelt.
Cathodoluminescence Yields in Highly Excited CdS
Authors: Egorov V. D. , Müller G. O. , Weber H. H. 
Published: July 2007

AbstractAn inner energy yield between 0.15 and 0.35 is obtained for the exciton emission, 489 and 493 nm, of CdS crystals at liquid nitrogen temperature under pulsed 9 ke V electron excitation at a pair‐production rate of about 1025 cm−3 s−1 below the lasing threshold. The CdS crystals were grown without deliberate doping. Emission at other wavelengths is less than 10%; the angular dependence of the radiation is of the form expected from classical optics. According to available experimental and theoretical data the pair‐production energy is equal to about three times the energy gap, hence the observed maximum energy yields correspond to a quantum yield of one. Therefore it would be expected that the transition to stimulated emission should be accompanied only by a spatial and spectral redistribution and not by an increase in efficiency.
On the τ‐Approximation in the Quantum Theory of the Conductivity Tensor
Authors: Stolz H. 
Published: July 2007

AbstractIn the framework of the random phase approximation a relaxation time is introduced into the quantum mechanical calculation of the conductivity tensor for a degenerate system of free electrons being elastically scattered by randomly distributed impurities. The result satisfies the requirements of gauge invariance and particle conservation and accounts for the modification of the level density by the scattering processes. In the special case of a weakly varying field the result obtained by Mertsching [6] is retained under certain conditions. Mertsching's semiphenomenological treatment is based on a heuristic formulation of the equation of motion for the statistical operator. The result is retained here if the Landau‐condition for the level width is met (i.e. the level width is much less than the Fermi energy). In the optical limit of zero wave number the Drude expression for the conductivity is obtained only for energies considerably less than the Fermi energy, otherwise a frequency‐dependent optical mass can be introduced.
Photoconductivity Oscillations in InP
Authors: Kovalevskaya G. G. , Nasledov D. N. , Slobodchikov S. V. 
Published: July 2007

AbstractThe oscillatory photoconductivity effect is found in n‐ and p‐type InP (n = 2 × 1015 cm−3, p = 1014 cm−3 at T = 300 °K) at 4.2 °K for the incident photon energy range 1.4 to 2.6 eV. The oscillations are the result of a strong interaction not only with longitudinal (in the photon range 1.4 to 1.58 eV) but also with the transverse (in the photon range 1.58 to 1.71 eV) optical phonons. For the incident photon range 1.7 to 2.6 eV the photoconductivity oscillations are considered to be connected with the emission of two phonons, probably TO(x) + TA(x). A possible explanation of the results is given. The interaction with the transverse mode is considered to arise from the fact that the constant‐energy surfaces in k‐space are not spherical and from the contribution of U‐processes.
Invariance of Sound Velocity Sums in Crystals
Authors: Fitzgerald E. R. , Wright T. W. 
Published: July 2007

AbstractA relation between the lattice dissociation energy D of a monatomic crystal, the atomic mass m, and a mean crystal sound velocity csrecently suggested by Fitzgerald in connection with his particle‐wave description of non‐elastic deformation in solids is reviewed. The cited relation D=m c2s implies that certain sound velocity sums in crystals are invariant and this is shown to be the case for crystals in which small atomic displacements can be described by linear elasticity. The proposed relation between lattice dissociation energy and a mean squared sound velocity is therefore entirely consistent with classical elasticity theory although, of course, not predicted by it.
Plastic Deformation of the Intermetallic Compound MgZn2
Authors: Paufler P. , Schulze G. E. R. 
Published: July 2007

AbstractThe behaviour of single crystal specimens of MgZn2 deformed by basal slip is investigated by both dynamic and creep tests at temperatures between 250 and 500 °C. With the dynamic experiments a smooth upper yield point is observed. The temperature dependence of the critical resolved shear stress and of the secondary creep rate, together with the stress dependence of the latter, are discussed in terms of a Peierls mechanism of plastic deformation. Some observations concerning slip band density, length, and height are given. It is concluded that the brittleness of MgZn2 is probably a consequence of its complex atomic structure.
A Method of Measuring Effective Electron Mass in Thin Insulating Films
Authors: Antula J. 
Published: July 2007

AbstractMA method is proposed for calculating the electron effective mass in thin insulating films (less than 100 Å) from the tunnel‐ and Schottky currents. In this method the slope of the Schottky characteristic provides the effective film thickness, and the slope of the tunnel characteristic leads to the electron effective mass. It is shown that, for uneven films, this method may provide better results than the calculation using the capacitance film thickness. The method is used to calculate the electron effective mass in a thin Ta2O5 film.
Zum dielektrischen Verhalten von Seignettesalz im Bereich der Decimeter‐ und Zentimeterwellen
Authors: Müser H. E. , Potthaest J. 
Published: July 2007

AbstractEs wird über Messungen der komplexen Dielektrizitätskonstante von Seignettesalz zwischen 0,5 und 4,5 GHz in der Umgebung des oberen Curie‐Punktes berichtet. Die Dielektrizitätskonstante folgt einer einfachen Debye‐Relaxation mit einer Relaxationsfrequenz, die oberhalb des Curie‐Punktes linear mit der Temperatur ansteigt. Die Relaxationsfrequenz für den Dielektrizitätsmodul ist praktisch temperaturunabhängig. Hieraus folgt durch eine einfache thermodynamische Betrachtung das von anderen Autoren bei hohen Frequenzen beobachtete Minimum der Dielektrizitatskonstante am Curie‐Punkt.
About the Fowler‐Nordheim Plots of Germanium Field Emitters
Authors: Ernst L. 
Published: July 2007

AbstractFowler‐Nordheim plots are obtained for tips of n‐type Ge with a resistivity of 5 Ωcm at room temperature. Atomically clean tip surfaces are obtained by field evaporation. The field‐current density vs. field strength characteristics are given, using the data obtained by Arthur regarding the field strength necessary for the field evaporation of Ge. These are compared with characteristics computed from Stratton's theory of field emission from semiconductors by using plausible values for the surface states parameters. The comparison shows that for Ge the effective work function for field emission is appreciably higher (≈︁5.8 eV) than would be expected from the literature. A value of Na < 1.7 × 1013 cm−2 is found for the density of surface acceptor states.
Electron Microscopic Contrast Effects at the Interface between Two Different Polytypes
Authors: Fourdeux A. , Gevers R. , Amelinckx S. 
Published: July 2007

AbstractA description is given of the δ‐type fringe pattern produced at the interface between a cubic and a hexagonal region within the same crystal. A discussion is given of the information which can be derived from a study of the nature of the outer fringes. Observations on a cobalt‐chromium 10% alloy are used to illustrate the theory. In this alloy the c/a ratio is found to be smaller than the ideal value. The stacking faults are found to be intrinsic.
Elektronenmikroskopische Untersuchung von Fehlstellen‐agglomeraten in ionenbestrahlten Kupferfolien. I. Analyse von Agglomerattyp und ‐konfiguration
Authors: Diepers H. 
Published: July 2007

AbstractEpitaktisch gezüchtete Cu‐Einkristallfolien wurden mit monoenergetischen Ar‐Ionen (5 keV) bestrahlt. Dabei werden Fehlstellenagglomerate erzeugt, die im Elektronenmikroskop als kleine, nicht näher auflösbare Punktkontraste sichtbar sind. Die Tiefenlage der Defekte in der Folie wurde mit Hilfe von Stereoaufnahmen ermittelt. Das hierzu verwendete Verfahren wird im einzelnen beschrieben. Der Defekttyp dieser Fehlstellen (Leer‐stellen‐ oder Zwischengitteratomagglomerate) und ihre Konfiguration werden auf Grund der Kenntnis ihrer Tiefenlage unter Anwendung der dynamischen Theorie des Kontrastes (Rühle et al.[2, 12]) bestimmt. Die Agglomerate sind aus Zwischengitteratomen aufgebaut und liegen überwiegend in Form Frankscher Versetzungsringe vor. Sie liegen alle in einem schmalen Tiefenbereich unterhalb der bestrahlten Oberfläche der Folie.
Röntgenwellenfelder in einem Dreistrahlfall
Authors: Hildebrandt G. 
Published: July 2007

AbstractGeburtstag gewidmet Die Grundgleichungen der dynamischen Theorie werden auf den Dreistrahlfall (000, 111, 11l) angewendet und gelöst. Es zeigt sich, daß die Dispersionsfläche aus drei Schalen‐paaren besteht, von. denen zwei ähnliche Eigenschaften haben wie die Schalenpaare des Zweistrahlfalles; insbesondere ist die zugeordnete Absorption stark erniedrigt bzw. erhöht, aber der minimale Koeffizient μ(3)⟂min ist weit kleiner als μ(2)⟂min des Zweistrahlfalles(000, 111). Die Wellenfelder des dritten Schalenpaares unterliegen etwa normaler Absorption. Folgende Eigenschaften symmetrischer Felder werden untersucht: Polarisation, Wellenlängen‐ abhängigkeit von μ(3)⟂min und μ(3)‖min, Intensitätsverteilung innerhalb der Felder mit μ(3)min und μ(3)max, Anpassung des Feldes mit μ(3)⟂min ans Gitter. Die Ergebnisse der Rechnungen stehen in befriedigender quantitativer übereinstimmung mit dem Experiment.
A Theory of X‐Ray Diffraction from an Ordered Alloy Containing Antiphase Domains
Authors: Roessler B. , Flinn P. A. 
Published: July 2007

AbstractThe theory of X‐ray diffraction from an ordered alloy containing antiphase domains is developed by expressing the Fourier coefficients that represent the diffracted intensity in a powder pattern in terms of a domain size distribution function. The size distribution function is expressed in terms of the second derivative of the Fourier coefficients and, hence, can be determined from experimental measurements of the superlattice peak shape. A comparison of these results to those of previous treatments of this problem shows that valuable additional information about the domain size distribution is accessible by means of the procedures presented here.
The Small Polaron Problem with an Application to Optical and DC Data of Reduced Barium Titanate
Authors: Reik H. G. , Heese D. 
Published: July 2007

AbstractReflectivity data from 1 to 12 μm for four samples of reduced BaTiO3 with dc conductivities between 20 and 240 (Ωcm)−1 are analysed in terms of small a polaron theory. Quantitative agreement between theory and experiment is found except for the sample with the highest conductivity. By fitting the optical data it is found that the parameters of the theory the average frequency of the optical phonons, Ω0, and the number η of phonons in the polarization cloud, have the values Ω0 = 1.265 × 1014 s−1 and η = 7. These parameters also determine the temperature dependence of the dc mobility. A weak temperature dependence of the mobility is found theoretically and is in agreement with the experimental data.
Piezowiderstandseffekt an Tellur. I. Experimente mit uniaxialem Druck parallel zur c‐Achse
Authors: Herrmann K. H. , Oelgabt G. 
Published: July 2007

AbstractAn Tellureinkristallen mit Akzeptorkonzentrationen zwischen 2,4 × 1014 und 6 × 1017 cm−3 werden die Piezowiderstandskoeffizienten π1133 und π3333 statisch gemessen. Im Eigenleitungsgebiet können die experimentellen Ergebnisse mit Hilfe des Deformationspotentialmodells quantitativ beschrieben werden. Im Störleitungsgebiet ist der Effekt temperaturunabhängig das spricht gegen das Auftreten zufälliger Entartungen im Valenzband.
Theory of Electric field Gradient due to Conduction Electron Charge Density Redistribution around Screw Dislocations in Metals
Authors: Ogurtani T. O. , Huggins R. A. 
Published: July 2007

AbstractThe electric field gradient due to conduction electron charge density redistribution around screw dislocations in metals is calculated. It is found that the electric field gradient behaves as r−5/2 cos(2 kF r + ϕ), where kF is the Fermi wave number and ϕ is the phase. The Bloch enhancement factor is computed using the orthogonalized plane wave procedure, and is found to be 7.62 for a screw dislocation in copper. These results are in agreement with nuclear magnetic resonance experiments in plastically deformed copper.
Magnetic Resonance in Higher Harmonics Generated by Free Carriers in Semiconductors
Authors: Kołodziejczak J. 
Published: July 2007

AbstractAn effect of higher harmonics generation by free carriers in semiconductors is discussed. It is shown that a large enhancement of nonlinear effects due to resonance at high magnetic fields can be observed. The effects discussed in the paper are associated with a non‐parabolicity of the band.
Derivation of Nucleation Kinetics in Solids by Examination of Plane Sections through the Samples
Authors: Toschev S. , Gutzow I. 
Published: July 2007

AbstractUsing a statistical approach, the basic formula is derived which relates the size distribution of spherical non‐communicating second phase particles embedded in a solid matrix to the distribution of their circular intersections revealed on an arbitrary plane through the specimen. Four types of crystallization kinetics are treated: steady state nucleation, transient nucleation, heterogeneous nucleation, and transient heterogeneous nucleation. The linear rate of crystal growth is assumed to be time‐independent in all cases. The corresponding size distribution functions in the volume and on the surface are derived. Their analysis permits the evaluation of important crystallization parameters from experimental data.
On the Phonon Drag Effect Contribution to Thermomagnetic Phenomena
Authors: Plăvttu C. N. 
Published: July 2007

AbstractCalculations are made of the acoustic and optical phonon drag effect contributions to some of the isothermal thermomagnetic coefficients. The scattering is considered to be a mixture of acoustic, optical, and ionized impurity scattering. It is found that the optical phonon drag is of more importance for the thermomagnetic effects than for the thermoelectric effects.
The Dielectric Permeability of Molecular Crystals
Authors: Davydov A. S. , Onishchuk V. A. 
Published: July 2007

AbstractThe quantum theory of the dielectric permeability of molecular crystals is developed on the basis of the quantum field equations and electronic excitation states of the crystals. The interaction between the molecules is considered to take place only through the field. The Green's function formalism is used.
Neutron‐Diffraction Study of AntiferroFerromagnetic Transition in a System of Ordered Fe(PdxPt1−x)3 Alloys
Authors: Kelarev V. V. , Sidorov S. K. , Klyushin V. V. , Abdulov R. Z. 
Published: July 2007

AbstractSome conclusions are made regarding the transition from antiferromagnetic to ferromagnetic structure in the ordered alloys of the system Fe(Pdx Pd1−x)3. This is based on an analysis of an experimental dependence of the intensity of the (100) ferromagnetic reflexion on the average magnetic moment per atom of the alloys of the system. It is concluded that the transition takes place through a set of complex magnetic structures with a noncollinear orientation of the atomic magnetic moments of the components.
Untersuchungen der Bereichstruktur von Nickeleinkristallen III. Die Abschlußstruktur in zylindrischen Kristallen mit 〈110〉 als Achse
Authors: Spreen H. 
Published: July 2007

AbstractDie Abschlußstruktur von zylindrischen Nickeleinkristallen mit 〈110〉 als Achse wird mit der Bitter‐Technik untersucht: Die senkrecht zur Stabachse gerichteten Magnetisierungskomponenten der Grundbereiche werden bei verschwindendem innerem Feld Hi von antiparallel zu den Grundbereichen magnetisierten Abschlußbereichen umgelenkt, deren Anordnung von der Oberflächenorientierung abhängt. Mit zunehmendem Feld Hi wird der Abschluß unabhängig von der Oberflächenorientierung mehr und mehr von magnetischen Streufeldern übernommen. Die Ladungen werden durch spezielle Oberflächenbereiche in das Kristallinnere verlagert.
Untersuchungen der Bereichstruktur von Nickeleinkristallen IV. Die Grundstruktur in zylindrischen Kristallen mit 〈100〉 als Achse
Authors: Spreen H. 
Published: July 2007

AbstractWir untersuchen an zylindrischen Nickeleinkristallen mit 〈100〉 als Achse die ferromagnetische Grundstruktur der Bereiche in niedrigen axialen magnetischen Feldern. Aus unseren Experimenten mit der Bitter‐Technik folgt zwangsläufig und widerspruchsfrei eine »zusammengesetzte Plattenstruktur«: Die Platten sind senkrecht zur Stabachse angeordnet: jede Platte umfaßt im wesentlichen vier Sektorbereiche. Die Sektorbereiche sind bei Hi = 0 Oe in einer leichten Richtung parallel zu der zugeordneten zweizähligen Oberfläche magnetisiert. Die zur Kristallachse senkrecht stehenden Magnetisierurgskomponenten haben innerhalb einer zusammengesetzten Platte einen Umlaufsinn, der von Platte zn Platte wechselt. Die vierzählige Symmetrie des 〈100〉‐Kristalls kommt somit in der magnetischen Bereichstruktur zum Ausdruck.
The Theoretical Strength of NaCl Crystals under Tension along its Body and Face Diagonals
Authors: Bartenev G. M. , Koryak‐Doronenko E. G. 
Published: July 2007

AbstractZwicky has proposed a method for calculating the theoretical strength of ionic crystals using Madelung's potentials for sign‐reverse rows. Using this method he has calculated the theoretical strength of NaCl crystals stretched along the edge of an elementary cube. This is a special case because the transverse compressive deformation along the y‐ and z‐axes is the same due tc the identical symmetry of the lattice in these directions. In the present paper Zwicky's method is generalized and extended to other directions of stretching in which contractions in mutually perpendicular directions are different. The theoretical strength and Young's moduli of NaCl crystals stretched along the body and face diagonals of an elementary cube are calculated.
EPR Study of Cu2+ Ion in Triglycine Fluoroberyllate
Authors: Stankowski J. 
Published: July 2007

AbstractAn investigation is made of the EPR spectrum of Cu2+ ions in ferroelectric triglycine fluoroberyllate. The values g∥ = 2.24 g∥ = 2.06, and A = 132 cm−1 are similar to those obtained for copper ions in triglycine sulphate and diglycine nitrate. The new lines are typical of S = 1 and the spectrum is found to have an anomaly at the Curie point. The D parameter of the spectrum is linearly dependent on the spontaneous polarization changes.