bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear Thermodynamics of Thermoelectric Phenomena in Ionic Semiconductors
Authors: Georgescu L. 
Published: July 2007

AbstractA theoretical study is made of nonlinear thermoelectric phenomena in semiconductors calculating the thermoelectric coefficients as a function of the phenomenological coefficients Lik for an ionic semiconductor. The interaction mechanism considered is the scattering of electrons and holes by acoustical and optical phonons. An expression for the entropy production is given assuming a nonlinear relationship between the coupled thermodynamic flows and forces.
Thickness Dependence of the Quantum Yield of Cesium‐Antimony Films
Authors: Deutscher K. , Hirschberg K. 
Published: July 2007

AbstractThe quantum yield of SbCs3 films is measured as a function of film thickness in the spectral range 440 to 546 nm. The quantum yield is calculated from the energy distribution within the layer as determined from optical constants and layer thickness, and from the attenuation length. The calculated curves agree well with the measured dependences for film thicknesses down to about 30 nm. Below 30 nm the measured curves bend off. Measurements of the conductivity show that the decrease of the quantum yield is not due to a change in the excitation or emission process, but to a steep rise of the electrical resistance of the film.
On the Behaviour of a Cylindrical Electron‐Hole Plasma in a Magnetic Field with Transverse Component
Authors: Brauer M. 
Published: July 2007

AbstractThe properties of a cylindrical semiconductor plasma generated by injection and placed in a longitudinal magnetic field with a small transverse component are investigated both for the stable and unstable state. The plasma is described by the macroscopic equations of motion and continuity for electrons and holes. For the stationary case formulae are derived and discussed concerning the density distribution of the plasma as well as the radial and azimuthal electric field. The investigation of the density instabilities follows a method developed by Johnson and Jerde for parallel fields. It is shown that the introduction of a transverse component of the magnetic field leads to a coupling of the modes. In the simplest case this causes the simultaneous appearance of the n = 0 and n = 1 mode with the same frequency above certain threshold values of the fields. On this basis an explanation of the oscillistor effect is possible.
Magnetic Domain Wall Dynamics
Authors: Feldtkeller E. 
Published: July 2007

AbstractSome calculations exist for the mobility and the effective mass of ferromagnetic domain walls of special wall structures. More generally valid derivations and formulas are presented here, which are not restricted to a special wall structure. It is shown that the nonlinearity observed by several authors in the dependence of the wall velocity on the field can be predicted theoretically if the material inhomogeneities causing the coercivity are taken into account in an appropriate manner. For a special example the existence of the wall contraction and the velocity limit shown by Enz for a wall without damping and without field is shown for a wall with damping and with field. As is the approximation by Enz, the present approximation also is not able to indicate the value of this velocity limit.
Influence of Uniaxial Stress on the Optical Properties of CdSe
Authors: Grynberg M. 
Published: July 2007

AbstractThe absorption edge, luminescence, and birefringence of CdSe single crystals under uniaxial stress are measured at 300 and 77°K. The Thomas‐Hopfield model of the valence bands is verified. Some relations between the components of the deformation potential tensors are obtained. The electron–phonon interaction term in dEg/dT at 300 and 77°K, respectively. The stress depencence of the bound exciton luminescence line and absorption edge is found to be the same.
Thermal Conductivity of Solid Ammonia
Authors: Krupskii I. N. , Manzhely V. G. , Koloskova L. A. 
Published: July 2007

AbstractThe thermal conductivity of solid ammonia is measured by the linear stationary method with continuous visual control of the sample state. The measurements are carried out in the temperature range 28 to 114°K. The temperature dependence of the thermal conductivity is discussed. The experimental method described in this paper has previously been used when studying the thermal conductivity of solid argon and methane.
The Nature of Oxide Layers on Single Crystals of Cadmium and Magnesium
Authors: Michell D. , Smith A. P. 
Published: July 2007

AbstractThe oxide layers formed on cadmium and magnesium single crystals on exposure to air at room temperature have been studied by electron diffraction, optical and electron microscopy, and X‐ray topography. A single crystal oxide layer of CdO2 is formed on cadmium with (111) parallel to (0001) and [110] parallel to [1120]. For magnesium, the oxide is a textured polycrystalline layer of MgO with an orientation relationship to the metal similar to that for cadmium and its oxide. The oxide layers on both metals are initially adherent but with increasing time of exposure to air, blisters form and cracking of the oxide occurs. The formation of oxide on cadmium produces visible defects within the crystal but no similar defects are observed in magnesium.
Flat Ferromagnetic, Epitaxial 48Ni/52Fe(111) Films of few Atomic Layers
Authors: Gradmann U. , Müller J. 
Published: July 2007

AbstractFlat epitaxial 48Ni/52Fe(111) films are prepared by evaporation onto atomically flat Cu(111) films. All films consisting of three or more layers (d ≧ 6 Å) show a far‐reaching fit to the model structure of a flat single crystal. The magnetic properties are determined for (70 ≦ T ≦ 400) °K with an oscillation type torsion magnetometer, which can detect a moment of 5 × 10−8 G cm3. All films of three or more layers are ferromagnetic without any indication of superparamagnetism; Curie‐temperature and magnetization decrease monotonously with film thickness; there is good qualitative agreement with spin‐wave theory and Green's function theory; the magnetization is independent of the field, however, within 1%, for (300 ≦ H ≦ 5000) Oe, while the theory predicts considerable dependence on the field. Strong anisotropies relating to the surface normal as easy axis may easily be interpreted as Néel‐type surface anisotropies.
Effect of Low Energy Electron and UV Irradiations on the Charge Condition of Etched Germanium Surfaces
Authors: Bose D. N. 
Published: July 2007

AbstractUsing field‐effect and contact potential difference (c.p.d.) measurements the effect of low energy (180 to 960 V) electron irradiation on etched germanium surfaces has been studied. On all n‐ and p‐type samples examined, a loss of negative charge was found to occur from the surface as shown by an increase in surface potential and decrease in c.p.d. with electron irradiation. Changes in c.p.d. were larger than changes in surface potential, the ratio being dependent on surface preparation. The difference between surface potential and c.p.d. changes can be explained by desorption of neutral atoms from the surface causing a change in surface dipole. UV irradiation above a threshold energy of approximately 5.0 eV was found to have a similar effect. If, however, dc fields were used for band‐bending, it was found that changes in surface potential and c.p.d. were equal and hence as expected no desorption occurred.
Untersuchung dreiwertiger Übergangsmetallionen in Silberhalogeniden. I. AgCl:V
Authors: Ulrici W. 
Published: July 2007

AbstractEs wird durch Messung der optischen Absorption und der Ionenleitfähigkeit nachgewiesen, daß V2+ im AgCl auf Kationenplatz unter Bildung einer zusätzlichen Silberlücke eingebaut wird. Durch Anlagerung von Defektelektronen (Anlaufreaktion mit Chlor) können diese V2+‐Ionen in V3+‐Ionen umgeladen werden. Die Umwandlung in dreiwertiges Vanadium wird wieder durch Messung der optischen Absorption nachgewiesen. Durch Messung der Ionenleitfähigkeit wird gezeigt, daß das V3+ auf Kationenplatz unter Bildung von zwei zusätzlichen Silberlücken pro V3+‐Ion substituiert bleibt. Durch Elektronenanlagerung (Kontakt mit Ag‐Metall) ist die Rückumladung des V3+ in V2+ möglich. Der Einfluß der Wechselwirkung der Silberlücken mit den dreiwertigen Kationen auf die Ionenleitfähigkeit wird berechnet und diskutiert.
Green's Function Calculation of Electro‐Optical Effects in Semiconductors. I. General Formalism and Interband Transitions
Authors: Porsch M. 
Published: July 2007

AbstractA general expression for the dielectric tensor induced by a light wave in the presence of a time‐dependent external electric field is given in terms of double‐time nonequilibrium Green's functions whose spectral representations are derived in the case of a static field. Neglecting field‐induced interband transitions, the poles of the one and two‐particle Green's functions for a Bloch electron in a static electric field are determined. The imaginary part of the dielectric function at the M0 edge is calculated for a lattice with no centres of inversion symmetry.
Radiation Hardening in Platinum
Authors: Galligan J. M. , Attardo M. J. 
Published: July 2007

AbstractSome measurements of the hardening introduced by fast neutrons in pure platinum are reported. It is found that the change in yield stress of neutron irradiated platinum varies as (Φt)1/2, in agreement with a lattice hardening mechanism. The rate of increase in damage, as observed with field ion microscopy in irradiated platinum, is compared with the rate of increase of yield stress for fixed total damage. This also indicates that the hardening is solely associated with depleted zones. Annealing studies of irradiated platinum, show that when vacancies are mobile, dislocation loops are formed from the vacancy clusters; the yield stress then varies as (Φt)1/3. Finally the total damage in the specimens is removed in the same temperature range where clusters of vacancies are removed.
Elektronenmikroskopie eingefrorener Versetzungen. II. Ergebnisse in den Bereichen I und II der Verfestigungskurve
Authors: Alexander H. 
Published: July 2007

AbstractGermaniumkristalle mittlerer Orientierung wurden bei 520°C dynamisch durch Zug verformt. Nach Verformung bis zu verschiedenen Punkten in den Bereichen I und II der Verfestigungskurve wurden die Kristalle unter Last abgekühlt. Dünne Folien parallel zur Hauptgleitebene und zu anderen {111}‐Ebenen wurden mit Transmissions‐Elektronen‐mikroskopie untersucht. Die Bilder zeigen eine ausgeprägte Ähnlichkeit der Versetzungsanordnung mit der in kubisch flächenzentrierten Metallen gefundenen. Das Peierlspotential hat keinen Einfluß auf den Verlauf der Versetzungen. Die Verteilung der Waldversetzungen wurde mit Ätzmethoden untersucht.
Optical Absorption by Polarons in Rutile (TiO2) Single Crystals
Authors: Bogomolov V. N. , Mirlin D. N. 
Published: July 2007

AbstractThe optical absorption in rutile single crystals doped with Nb and other impurities as well as partially reduced is investigated in the temperature range 10 to 900°K. It is shown that the spectrum and the magnitude of the optical absorption by current carriers can be satisfactorily explained in terms of the small polaron theory. The oscillator strength for the absorption band studied as well as the polaron binding energy, the mean electron‐phonon coupling constant, and the nearest neighbour overlap integral are estimated from the experimental data.
Effect of Phonon Drag on the Kinetic Properties of Alloys
Authors: Masharov S. I. 
Published: July 2007

AbstractThe kinetic coefficients, i. e. the electrical conductivity, thermal conductivity, and thermo e.m.f. of a binary ordered alloy are calculated on the basis of the many‐electron model of an alloy previously used in [1] taking into account the non‐equilibrium of the phonon system. It is shown that at low temperatures phonon drag becomes important and leads to qualitatively new temperature dependence of the kinetic coefficients as compared to pure metals. Under definite conditions in the electrical resistivity vs. temperature curves a minimum and maximum may occur.
Ultrasonic Attenuation in Unirradiated and Neutron Irradiated Quartz
Authors: Fitzgerald T. M. , Silverman B. D. 
Published: July 2007

AbstractThe ultrasonic attenuation of unirradiated and neutron irradiated quartz is discussed in terms of recent theoretical formulations of the three‐phonon scattering mechanism. It is shown that the temperature dependence of the attenuation in the unirradiated quartz crystal can be understood by invoking this scattering mechanism. It is also shown that upon neutron irradiation the observed changes in the attenuation can be qualitatively understood by assuming that neutron irradiation decreases the thermal phonon lifetimes in the crystal.
Untersuchung dreiwertiger Übergangsmetallionen in Silberhalogeniden. II. Chrom und Titan
Authors: Ulrici W. 
Published: July 2007

AbstractDurch Messung der optischen Absorption und der Ionenleitfähigkeit wird gezeigt, daß Cr2+‐Ionen, die auf Kationenplätzen im AgCl und AgBr eingebaut sind, durch Anlagerung von Defektelektronen in Cr3+‐Ionen auf Kationenplätzen umgewandelt werden können. Die Anlagerung von Elektronen führt zur Rückumwandlung des Cr3+ in Cr2+. Die Untersuchung der optischen Absorption und der Ionenleitfähigkeit titandotierter AgCl‐ und AgBr‐Kristalle zeigt, daß Ti3+ auf Kationenplätzen eingebaut wird.
The Temperature Dependence of the Flow Stress of Copper Single Crystals
Authors: Bullen F. P. , McK. Cousland S. 
Published: July 2007

AbstractIt is shown that the Cottrell‐Stokes ratios of copper single crystals are not constant during tensile deformation in stages II and III at temperatures from 77 to 443°K. However, there appears to be a fixed relationship between the Cottrell‐Stokes ratio and the flow stress (as measured at a standard temperature). This relationship is independent of crystal orientation and the temperature or stage of deformation. The relationship is similar to that previously reported for polycrystalline copper [1], although not quantitatively identical. These relationships have been interpreted as evidence that the obstacles responsible for temperature‐dependent hardening are formed by the action of stresses from arrays of primary dislocations. The nature of the unloading yield point and its relevance to the reversible change in flow stress are also discussed.
Untersuchungen zur Deutung der kantenfernen Feinstruktur der Röntgen‐K‐Absorptionsspektren
Authors: Brümmer O. , Dräger G. 
Published: July 2007

AbstractDie physikalischen Voraussetzungen der Fernordnungs‐ und Nahordnungstheorien zur kantenfernen Feinstruktur der Röntgen‐K‐Absorptionsspektren kristalliner Festkörper werden überprüft. Aus der Literatur bekannte Spektren von amorphem Ge und glasigem GeO2 sowie eigene Messungen an wassergelöstem K3 [Fe(CN)6] werden interpretiert. Im Spektrum dieser Substanzen, deren atomarer Aufbau nur Nahordnungen und keine Fernordnung besitzt, tritt trotzdem eine kantenferne Feinstruktur auf. Ihre Existenz sowie die weitgehende Übereinstimmung mit den entsprechenden Absorptionsstrukturen der kristallinen Zustandsformen dieser Stoffe weisen somit deren kantenferne Feinstrukturen als Nahordnungseffekt aus.
Electron Microscope Image Profiles of Paired and Triple Dislocations
Authors: Murphy R. J. , Crawford J. L. 
Published: July 2007

AbstractNumerical solutions for the dark field images which arise when electrons pass through thin films containing paired or triple dislocations have been obtained for conditions under which the kinematical approximation holds. The results show that the diffraction contrast of any dislocation in a group is a sensitive function of the relative position of that dislocation in the group. There are arrangements where some dislocations can be out of contrast even though the individual dislocations which come together to form a pile‐up or group may be in strong contrast. The results point to the extreme care which should be used when evaluating electron micrographs of dislocation structures, particularly when there is a measure of strain field overlap amongst the dislocations.
The Self‐Energy of a Dislocation and the Elastic Energy of Piecewise Straight Dislocation Configurations
Authors: Jøssang T. 
Published: July 2007

AbstractA comparison is made of the models of Bullough and Foreman [1], and of Kröner [2] and Jøssang et al. [3] for determining the self‐energy of a straight dislocation. The differences and their physical implications are pointed out. It is concluded that, from a physical point of view, the methods of Kröner and Jøssang et al. are the more correct ones. A discrepancy between the formula of Jøssang et al. [3] and that of de Wit [4] for the interaction energy between two straight dislocation segments is shown to disappear when an error in de Wit's formula is corrected.
Combined Infrared Photoemission From Cs3Sb
Authors: Hora H. , Kabiersch G. B. 
Published: July 2007

AbstractThe time dependence of the photoemission current of Cs3Sb cathodes shows at high light intensities a Boltzmann factor with an activation energy of 0.08 eV (according to an IR radiation of 15 μm wavelength). In order to study the influence of infrared radiation on the usual photoemission process Cs3Sb layers are irradiated with broad band radiation of 2 μm wavelength. This infrared radiation alone produces no emission current. The photoemission caused by light of a sufficient high intensity to which the cathode is sensitive, however, is changed by the infrared radiation up to quantum efficiencies of 10−3 additionally emitted eletcrons/IR photon. This combined photoemission can be a positive or negative effect.
Magnetisierung in der Umgebung unmagnetischer Einschlüsse in Ferromagnetika
Authors: Dietze H.‐D. , Schröder K. 
Published: July 2007

AbstractSchneidet man aus einem Ferromagneten einen Hohlraum heraus, so wird die Verteilung der Magnetisierungsrichtung in der Umgebung des Hohlraums in komplizierter Weise verändert. Sind diese Änderungen gegenüber dem Ausgangszustand klein, so lassen sich die mikromagnetischen Gleichungen linearisieren. Als Ausgangszustand werden die Magnetisierungsverteilung einer Blochwand und der homogen magnetisierte Zustand mit einem homogenen äußeren Feld behandelt.
Magnetisierung in der Umgebung unmagnetischer Einschlüsse in Ferromagnetika. II. Kugelförmige Hohlräume in Ferromagnetika ohne Wände
Authors: Schröder K. , Dietze H.‐D. 
Published: July 2007

AbstractEs wird die Magnetisierungsverteilung in der Umgebung eines kugelförmigen Lochs mit den in Teil I angegebenen Gleichungen berechnet. Hieraus wird dann die Energie und der Einfluß von Löchern auf das Einmündungsgesetz in die ferromagnetisch Sättigung abgeleitet.
Mössbauer Experiments with Coulomb‐Excited 73Ge after Coulomb Recoil Implantation
Authors: Zimmermann B. H. , Jena H. , Ischenko G. , Killan H. , Seyboth D. 
Published: July 2007

AbstractThe nuclear resonance absorption of the 67.03 keV de‐excitation radiation of 73Ge*, Coulomb‐excited by 20 to 30 MeV 16O ions, is studied. The recoiling 73Ge° nuclei are implanted into a chromium substrate. The electronic configurations Ge (4s1 p3) in Ge (cryst.), Ge (15% (4s2 p0), 85% (4s2 p2)) in Ge (II)Se, Ge (62% (4s0 p0), 38% (4s1 p3)) in GeO2 (hex.) and GeO2 (tetr.), and the ratio δ R/R=1.12 × 10−3 of the nuclear charge radius are compatible with the measured isomeric shifts. Line broadenings and recoil‐free fractions f of the implantation target and the absorbers are determined. At 78 °K f is greater than f by a factor of six.
On the Reverse‐Biased Capacitance of Step p+‐n Junctions with Traps
Authors: Auth J. 
Published: July 2007

AbstractThe steady‐state occupation of multiple chargeable deep trap levels of a depletion‐layer is calculated. Using this result, the capacitance of reverse‐biased p+‐n step junctions with traps is obtained by integration of the Poisson equation. It is shown that measurements of the ac and dc capacitance of the p‐n junction with traps and of the capacitance of an equivalent junction without traps give some information about the capture cross‐section ratios for electrons and holes of the trap levels.
On the Theory of Low‐Temperature Exciton Absorption Spectra
Authors: Fedoseev V. , Hizhnyakov V. 
Published: July 2007

AbstractThe absorption spectrum of Wannier‐Mott excitons at low temperature is studied in the case of weak exciton–phonon coulping. The one‐phonon approximation is used. Only the interaction of excitons with acoustic phonons is taken into account. It is shown that for low temperatures (k0T ≪ 2 m c2) the exciton spectrum consists of a resonant line with its halfwidth tending to zero if T → 0, and of a phonon wing of finite width with the maximum being shifted from the resonant line. In the case T = 0 the resonant line appears to be a zero‐phonon line and the wing represents the vibrational recurrences of the first.
Electronic Absorption Spectrum of K2CoF4
Authors: Tiwari J. S. , Mehra A. , Srivastava K. G. 
Published: July 2007

AbstractThe optical absorption of K2CoF4 has been measured and compared with that of KCoF3. The observed bands are assigned to transitions from the ground state to various excited levels of Co2+ in Oh symmetry and the band positions are fairly well fitted with B = 890 cm−1, Dq  840 cm−1, and C = 4.4B.
Consideration of Polarization and Covalency Corrections to the Quasi‐Coulomb Shift of Optical Lines of Ion Pairs in Crystals
Authors: Cherepanov V. I. , Nikiforov A. E. 
Published: July 2007

AbstractThe effect of polarization and covalency corrections on the Coulomb interaction of impurity ion pairs in ionic crystals is taken into account. A simple semi‐empirical theory is suggested for the explanation of the quasi‐Coulomb shifts of the optical lines belonging to the pairs of equivalent impurity ions (in relation to the corresponding lines of single impurity ions). In this theory we use effective charges and effective electric dipole moments of ions. The theory is applied to the explanation of the optical spectrum of Cr3+Cr3+ pairs in ruby. The problem of a microscopical calculation of effective parameters is discussed.
Spin‐Wave Distribution Function and Thermodynamics of the Heisenberg Ferromagnetic
Authors: Mitsek A. I. , Kolmakova N. P. , Feigin V. A. , Gaidanskii P. F. 
Published: July 2007

AbstractThe application of the elementary excitation theory to the spin system of a ferromagnetic is investigated on the basis of the Heisenberg model. It is found that the spectrum of elementary excitations considered as a gas of quasi‐particles, and their distribution function are completely determined by the Hamiltonian of the system. The spectrum of the transverse spin waves and the distribution function both of the transverse and the longitudinal spin waves are calculated by the double‐time anticommutator Green's function method. Since the distribution functions have no singularities, it is possible to obtain expressions for the thermodynamic quantities in the form of convergent power series in a small parameter τ T/Tc. Expressions for the specific heat and the spontaneous magnetization of a ferromagnetic are calculated.
Forbidden Transitions (ΔM  2) Induced by an Axial Crystal Field in Electronic Paramagnetic Resonance
Authors: Marti C. , Romestain R. , Visocekas R. 
Published: July 2007

AbstractFor certain angles between an applied magnetic field and the optical axis of a crystal, magnetic dipolar transitions ΔM = 2; Δm = 0, ± 1 (M and m: electronic and nuclear azimuthal quantum numbers) can be induced by an axial crystal field, including hyperfine interaction. We calculate the corresponding oscillator strengths for a level with effective spin S (2 S + 1 odd). These results can be applied to paramagnetic resonance near g = 4 of Mn++ in wurtzite.