bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impurity Scattering in the Theory of Interband Magneto‐Optical Effects
Authors: Korovin L. I. , Kharitonov E. V. 
Published: July 2007

AbstractThe quantum theory of the line‐shape of oscillatory interband magneto‐optical effects in the region of the intrinsic absorption edge in semiconductors is developed for the case of non‐stationary electron states arising from the scattering of electrons by an impurity atom with a short‐range (repulsive) potential. The peculiarity of the problem is that a first‐oder perturbation treatment of the interaction parameter is inadequate, and in order to obtain finite expressions for the function −iW = Λ + iΓ in the vicinity of resonance it is necessary to sum an infinite series which represents the individual terms of the kinetic equation. The cases of low impurity‐atom concentration and high concentration with weak interaction (when the one‐particle approximation is still valid) are considered in detail. −iW is found to depend, in general, on the concentration of charge carriers, their interaction with impurity atoms, the frequency of the light, the electron momentum, and various parameters of the band structure.
Bitter Patterns on Nickel Ferrite Single Crystals
Authors: Rosenberg M. , Tânâsoiu C. , Nowicki L. 
Published: July 2007

AbstractThe Bitter patterns on the (111) and (110) natural faces of nickel ferrite single crystals, grown by the flux melt method, are investigated. The internal domain structure consists of three sets of parallel domains magnetized along the [111], [111] and [111] directions and separated in each set by 180° Bloch walls and by 71° walls between sets. The complex structure of the Bitter patterns on the (111) plane is due to the tendency for domains of reverse magnetization to be formed. The magnetization process involves both displacement and rotation of the walls.
Substructure of Persistent Slip Bands in Cyclically Deformed Copper
Authors: Lukáš P. , Klesnil M. , Krejčí J. , Ryš P. 
Published: July 2007

AbstractThe dislocation distribution in the surface layer of cyclically deformed specimens of polycrystalline copper is studied by means of transmission electron microscopy of thin foils, both parallel and nonparallel to the surface. The distribution within the surface layer and near the persistent slip bands is found to differ considerably from that inside the specimens. The persistent slip bands consist of zones of alternately high and low dislocation density. The zones of high density link together at a particular depth below the surface. The zones of low density are assumed to serve as “channels” in which the motion of dislocations emitted from Frank‐Read sources is relatively free. The escape of these dislocations from the free surface results in surface extrusions.
Theory of Space‐Charge‐Limited Currents in Thin Semiconductor Layers
Authors: Geurst J. A. 
Published: July 2007

AbstractThe current flowing in a thin semiconductor layer between two knife‐like contacts located on the same side of the layer is analyzed using a model in which the thicknesses of the layer and the electrodes are taken to be negligible compared with the separation of the electrodes. Since the excess density of mobile charge in the layer is controlled by the transversal component of the electric field, side effects play a dominant part in the model. The calculated current‐voltage characteristic shows a transition from ohmic to space‐charge‐limited behaviour at increasing voltages. The space‐charge‐limited current at higher voltages is inversely proportional to the square of the electrode distance. This dependence was found experimentally by Polke, Stuke and Vinaricky. The effect of traps is taken into account by means of a simple model. If empty traps are present at zero electric field, the theory yields a threshold potential beyond which the current starts flowing.
Neutron Investigation of Temperature Effects in the Magnon Spectrum of Magnetite
Authors: Dimitrijević Ż. , Kraśnicki S. , Rżany H. , Todorović J. , Wanic A. 
Published: July 2007

AbstractThe diffuse magnon scattering peaks connected with τ = (111) in magnetite are examined at a number of temperatures using neutrons with λ = 1.314 Å. The decrease in magnon energies at elevated temperatures is observed and compared with the theory of Mills et al. [10]. Pronounced temperature dependent asymmetry of the magnon low energy peak is found.
Mößbaueruntersuchungen an Co57‐dotiertem AgCl
Authors: Hennig K. , Meisel W. , Schnorr H. 
Published: July 2007

AbstractMößbaueruntersuchungen bei 77, 195 und 297 °K an Co57‐dotierten AgCl‐Polykristallen lieferten folgende Ergebnisse: Die bei 77 und 195 °K auftretenden Spektren können durch Fe++, das auf Kationenplatz eingebaut und mit einer Kationenlücke assoziiert ist, gedeutet werden. Die auf reines Eisen bezogene Isomerieverschiebung beträgt (1,32 ± 0,05) mm/s bzw. (1,25 ± 0,05) mm/s und die Quadrupolaufspaltung (1,07 ± 0,07) mm/s bzw. (0,74 ± 0,07) mm/s für 77 bzw. 195 °K. Bei 297 °K, beträgt die Isomerieverschiebung (1,15 ± 0,05) mm/s, die Quadrupolaufspaltung ist kleiner als 0,3 mm/s. Das anomale Verhalten der Quadrupolaufspaltung bei 297 °K wird durch eine genügend schnelle Rotation der Kationenlücke um Fe++ gedeutet. Die Ergebnisse werden mit bekannten Werten für Co57‐dotiertes NaCl verglichen und die auftretenden starken Abweichungen diskutiert.
Wechselwirkungen und Verteilungskurven hartmagnetischer Teilchenkollektive
Authors: Henkel O. 
Published: July 2007

AbstractEs wird experimentell gezeigt, daß bei hartmagnetischen Teilchenkollektiven ohne Wechselwirkung die Verteilung log‐normal ist. Wenn die ermittelten Abweichungen bei praktischen Kollektiven auf die Wechselwirkungen der Teilchen untereinander zurückgeführt werden, lassen sich Angaben über die Art und Größe der Wechselwirkungsfelder machen. In der Regel bestehen sie aus einem positiven, magnetisierungsunabhängigen und einem negativen, magnetisierungsunabhängigen Term. Bei Cu‐Ni‐Fe‐Legierungen läßt sich die Wechselwirkung in 1. Näherung sogar nur durch den magnetisierungsunabhängigen Term beschreiben.
Origin of Quadrature Flux in Magnetic Films
Authors: Harte K. J. , Cohen M. S. , Weiss G. P. , Smith D. O. 
Published: July 2007

AbstractSeveral investigators have studied flux varying in quadrature with a small ac field applied to a magnetic film in the presence of a perpendicular dc field, i.e., the imaginary part of the susceptibility. This phenomenon has often been interpreted as arising from magnetic switching in scattered regions where the net field crosses the tip of either uniaxial, complex biaxial, or negative anisotropy astroids. The viewpoint taken here, however, is that the quadrature flux originates in local irreversible reorientations of the magnetization ripple. This model is supported by experiments in which quadrature flux was measured as a function of dc field magnitude for three different field configurations chosen so that for a given field value the ripple state was the same in the three configurations.
Changes in Ag2O Films
Authors: Rollins T. L. , Weichman F. L. 
Published: July 2007

AbstractThin films of Ag2O were deposited on a cooled substrate by cathodic sputtering of silver in a low pressure oxygen atmosphere. The effects of ageing at room temperature and the effects due to slight heating in air are studied through the changes of electrical resistance, optical absorption and photoconductivity. It is proposed that the fresh films contain a greater excess of oxygen over the stoichiometric Ag2O than the final higher resistance material. Unless mechanically disturbed, the films did not reduce to silver over periods up to one year.
Crystal Symmetry and Magnetic Structures
Authors: Verschueren M. 
Published: July 2007

AbstractSymmetry considerations are used to determine the possible magnetic structures for a given crystal. The magnetic moment density is defined in two ways: (1) from the quantum mechanical definition of spin density, (2) from the classical concept of an array of magnetic moments. Since both definitions should have the same transformation properties, restrictions can be placed on the possible magnetic structures. Some applications of this theory are suggested.
Strahlungsdefekte in deuteronenbombardierten CdS‐Kristallen
Authors: Schweinberger W. , Wruck D. 
Published: July 2007

AbstractAn CdS‐Einkristallen wurden vor und nach einer Bestrahlung bei 150 °K mit 13,5 MeV‐Deuteronen Untersuchungen der Dunkelleitfähigkeit, der spektralen Verteilung der Photoleitfähigkeit, der Lebensdauer der Leitungselektronen und des Hafttermspektrums durchgeführt. Die Konzentration der durch Kernumwandlungen erzeugten Fremdatome Indium und Zinn wurde durch γ‐Spektroskopie ermittelt. Aus den elektrischen Messungen folgt, daß durch den Beschuß mit einer effektiven Erzeugungsrate von ca. 5 × 10−3 cm−1 Defektniveaus bei Ec – 0,10 eV, Ec –0,42 eV und Ec –0,65 eV mit Einfangquerschnitten für Elektronen von 5 × 10−15, 1 × 10−14 bzw. 5 × 10−14 cm2 gebildet werden, die bei Raumtemperatur stabil sind. Das Zentrum bei Ec –0,42 eV tritt sowohl als Haftterm als auch als Donator in Erscheinung. Das Verhalten der Lebensdauer deutet auf die Vergrößerung der Konzentration von “class II” Rekombinationszentren bei ca. Ey + 0,15 eV hin. Es wird eine Deutung hinsichtlich der Natur der strahlungserzeugten Defektniveaus vorgeschlagen.
Stacking Faults in TiC
Authors: Venables J. 
Published: July 2007

AbstractTiC single crystals doped by diffusion with 100 ppm of boron have been examined by transmission electron microscopy. Stacking faults, approximately 1 μm wide, bounded by partial dislocations were observed in all doped samples. It is considered that the faults serve as nucleation sites for the “Mondrian precipitates” observed by Williams [1].
Ferroelectric Properties of Solid Solutions of Triglycine Sulfate and Fluoberyllate Crystals
Authors: Březina B. , Šafránková M. , Kvapil J. 
Published: July 2007

AbstractA series of solid solutions of ferroelectric TGS and TGFBe single‐crystals are prepared by crystallization from aqueous solutions. This procedure allows the phase transition from the ferroelectric to the paraelectric state to be varied in the temperature range 48.5 to 70°C. The temperature of the phase transition is not a linear function of the composition of the mixed single‐crystals. The temperature dependence of the permittivity of solid solutions of all concentrations obeys the Curie‐Weiss law.
Theoretical Phonon Spectra and Heat Capacities of Solidified Argon and Krypton
Authors: Gupta N. P. , Dayal B. 
Published: July 2007

AbstractThe phonon spectra of solidified Argon and Krypton have been calculated on the basis of the Born‐Karman theory using the interatomic potential ϕ(r) = ‐Ar−6 + AB × exp (‐r/Q), and taking into account the zero‐point energy and interactions of the four nearest neighbours. The evaluation of the parameters A, B, and Q requires a knowledge of the vibration spectrum of the crystal which is itself a function of these constants. A method of iteration is therefore employed to evaluate the potential parameters, after estimating the frequency‐dependent terms using the Debye theory of specific heats. The static lattice energy is obtained by a method of successive approximations. The specific heats and (θ,T) curves show a fair agreement with the experimental results.
Magnetic Susceptibility of Iron‐Rich Face‐Centered Cubic Iron‐Palladium Alloys
Authors: Arajs S. 
Published: July 2007

AbstractMass magnetic susceptibility of f.c.c. iron‐palladium alloys containing 1.0, 3.0, 4.9, 7.9, 10.0, 11.9, and 15.3 at% palladium has been measured up to 1500 °K. These alloys and pure f.c.c. iron do not follow the Curie‐Weiss law. The 1/τT vs. 1/T plots, where τ is the magnetic susceptibility and T the absolute temperature, reveal indirectly the antiferro‐magnetic nature of iron. The antiferromagnetic interaction is gradually reduced by alloying with palladium.
Transition Radiation from Three‐Layered Foils
Authors: Steinmann W. , Wille H. 
Published: July 2007

AbstractA general expression is derived for the transition radiation from a foil consisting of three different layers with arbitrary dielectric constants and thicknesses. This expression is used to calculate transition radiation from oxide‐covered Al foils. The results are compared with the experimental data of Herickhoff et al. [7]. Almost perfect agreement between theory and experiment can be achieved if the oxide layers are taken into account.
Energieverluste schneller Elektronen in Alkalihalogenidschichten und ihre Winkelabhängigkeit
Authors: Geiger J. , Odelga P. , Pfeiffer H.‐Chr. 
Published: July 2007

AbstractDie Energieverlustspektren schneller Elektronen nach dem Durchgang durch Alkalihalogenidschichten wurden aufgenommen. Ein Energieverlust in jedem Spektrum stimmt mit dem Wert überein, der sich formal aus der Plasmafrequenz freier Valenzelektronen ergibt. Die experimentelle Überprüfung der Dispersionsbeziehung zeigt jedoch, daß der Betrag der betreffenden Energieverluste innerhalb der Meßgenauigkeit vom Streuwinkel unabhängig ist, im Gegensatz zu den Messungen von Sueoka [3]. Daher können diese Energieverluste nicht auf der Anregung freier Elektronen beruhen. Die Intensität der unter‐suchten Energieverluste nimmt mit steigendem Streuwinkel etwa proportional zu ϱ−2 ab.
Dissociation of Dislocations on {110} Planes in Anisotropie B.C.C. Metals
Authors: Vítek V. 
Published: July 2007

AbstractThe dissociation of dislocations with Burgers vectors 1/2〈111〉 and 〈100〉 on {110} planes in b.c.c. metals is studied. An analysis of the possible dissociations is carried out for eleven b.c.c. metals using anisotropic elasticity theory. For those dissociations which are found to be energetically favourable, the widths of the extended dislocations are computed as functions of the stacking fault energy.
Atomic Motion in Hydrogen‐Bond Ferroelectrics
Authors: Villain J. , Stamenković S. 
Published: July 2007

AbstractAnharmonic atomic motion in ferroelectrics may, in certain cases, be described in terms of a harmonic scheme by introducing a quasi‐spin formalism. In this paper the frequency spectrum is investigated first at zero temperature, using a spin‐wave approximation, then at finite temperatures, using a molecular‐field approximation and neglecting damping and its consequences. The results are discussed with reference to neutron scattering experiments, and a brief description of the critical phenomena is given.
Minoritätsträger in CdS I. Photospannung bei optischer Anregung innerhalb und außerhalb der Eigen‐absorption als Minoritätsträgereffekt
Authors: Palz W. , Ruppel W. 
Published: July 2007

AbstractDie stationäre Leerlauf‐Photospannung in den untersuchten monokristallinen CdS‐Proben wird durch Erzeugung freier Minoritätsträger d. h. Löcher hervorgerufen. Dies wird auch für Belichtung mit Wellenlängen jenseits der Absorptionskante gezeigt, indem die Photospannung mit der Tilgung der Majoritätsträger‐Photoleitung verglichen wird. Aus der Beobachtung einer reversiblen Tilgung der Photoleitung, durch Belichtung jenseits der Absorptionskante erzeugt, wird geschlossen, daß unter diesen Bedingungen freie Majoritätsträger nur durch einen Zweistufenprozeß erzeugt werden, während freie Minoritätsträger in einem Einstufenprozeß aus diskreten Termen angeregt werden können. Wenn zusätzlich zu einer Photospannung, die durch Belichtung in der Nähe der Absorptionskante erzeugt wird, eine Photospannung durch eine Belichtung mit längeren Wellen hervorgerufen wird, stimmt die Beziehung zwischen diesen Spannungen quantitativ mit einer Theorie überein, die auf der Erzeugung einer Photospannung durch freie Minoritätsträger im Photoleiter beruht. Während die stationäre Photospannung am Metall‐CdS Kontakt allein durch Berücksichtigung der Minoritätsträgererzeugung verstanden werden kann, erfordert die Erklärung des Kurzschluß‐Photostromes die Berücksichtigung der freien Majoritäts‐ sowie Minoritätsträger.
Linear Equations for the Green's Functions of Crystal Lattices. A Possibility of Approximate Calculation
Authors: Kunc K. 
Published: July 2007

AbstractConsideration of translational and rotational symmetry substantially reduces the number of Green's functions (elements of reciprocal dynamical matrix), which must be computed. In the present paper a method is proposed which further reduces this number by finding a set of linear equations for the Green's functions; these sets are given for b.c.c. and s.c. lattices. A method for approximate calculation of Green's functions is also proposed.
On the Infra‐Red Absorption of Crystals Due to Lattice Vibrations
Authors: Wehner R. 
Published: July 2007

AbstractThe theory of the infra‐red absorption and dispersion of crystals due to lattice vibrations is reinvestigated. Dipole moments up to third order and cubic and quartic anharmonicity in the displacements of the nuclei are considered. Using Green functions and the functional method of Martin and Schwinger a dispersion formula is derived in terms of renormalized phonons. The introduction of a renormalized linear dipole moment causes the oscillator strength to become a complex function of frequency. In the case of diatomic ionic crystals the frequency shift and lifetime of the dispersion oscillator can be obtained from the measured optical parameters.
On the Angular Dependence of Sputtering and Kinetic Electron Emission of Single Crystals
Authors: Martynenko Yu. V. 
Published: July 2007

AbstractThe dependence of the sputtering yield K on the angle of incidence ϕ is calculated for single crystals by taking into account multiple collisions of the ions with atoms of the crystal. The secondary collisions increase the maxima of the curve K(ϕ) but do not alter the form of the minima. The effect of lattice defects on the function K(ϕ) is also considered. These defects mainly alter the minima in K(ϕ) and on the whole decrease the anisotropy of the sputtering yield. Electron emission from single crystals due to ion bombardment is treated in a similar way assuming a kinetic emission mechanism.
Jahn‐Teller Distortions and Inversion Splitting for Transition Metal Complexes and Local Centres in Crystals with Degenerate Electronic T‐terms
Authors: Bersuker I. B. , Vekhter B. G. 
Published: July 2007

AbstractIt is shown that the Jahn‐Teller equivalent configurations of a threefold degenerate electronic T‐term do not seem to correspond to pure tetragonal or pure trigonal distortions as expected from the work of Opik and Pryce [10]. The conclusions of the latter work appear to be valid only to first approximation. The distortions of tetragonal minima under trigonal displacements are obtained. This shows that inversion splitting does occur as predicted earlier [1], in contrary to the statements of Ham [9]. The results of the theory are in agreement with the last experiments by Sturge [8].
Comments on Paraelectric Resonance
Authors: Sauer P. , Schirmer O. , Schneider J. 
Published: July 2007

AbstractThe conditions under which paraelectric resonance can be observed are investigated. Paraelectric resonance is defined as a resonant transition between energy levels formed by a site‐degenerate electric dipole in a crystal. Possible applications of the present theory may be found in systems of the type KCl:OH−. In these systems the ground state of the impurity ion has a sixfold site degeneracy which is removed by the tunnel effect and the electric field. Low temperature anomalies of the static dielectric constant caused by the tunnel effect are also discussed.
An Absolute Determination of the Extrinsic and Intrinsic Stacking Fault Energies in AgIn Alloys
Authors: Gallagher P. C. J. 
Published: July 2007

AbstractObservations have been made of extrinsic‐intrinsic node pairs, and of a hitherto unreported fault pair. It is shown that a simple estimate of the ratio of extrinsic to intrinsic stacking fault energy (γe/γi) cannot be made from the inscribed radii of node pairs, and that earlier qualitative results that γe/γi > 2, or more, are invalid. The simple geometry of the new fault pair facilitates a straight forward absolute determination of both γe and γi. Contrary to published results, γe and γi have been found to be approximately equal. For the present alloys, γe/γi = 1.09 ± 0.1 (for the electron —atom ratio e/a = 1.15) and γe/γi = 1.03 ± 0.1 (for e/a = 1.23). Good absolute agreement has been obtained between γi determined from the fault pairs, and from the observation of extended three‐fold nodes. It is concluded that extrinsic faults are rarely observed because of a high impedance to their formation arising from the co‐operative glide which is necessary, but that, once formed, the extrinsic fault energy is closely the same as the intrinsic.
Colour Centres in X‐Irradiated NaCl:Ag and NaCl:(Ag + Ca) Crystals
Authors: Topa V. , Haragea S. 
Published: July 2007

AbstractA study is made of colour centres induced by X‐irradiation at room temperature in NaCl:Ag and NaCl:(Ag + Ca). It is shown that the induced bands in NaCl:Ag are strongly dependent on the concentration of Ag as well as on the irradiation time and also that the B‐, C‐, and D‐bands have a complex structure. Three components of the B‐band, four of the C‐band and two of the D‐band are found at liquid nitrogen temperature. Optical bleaching in the F‐light shows that only a component of the B‐, C‐, and D‐bands is definitely electronic. It is also noted that only the optical bleaching of the F‐band in NaCl:Ag results in a simple B‐band much like that obtained by electrolytic colouring. The incorporation of both Ca and Ag in NaCl and subsequent X‐irradiation lead to very intensive B‐ and D‐bands which are shifted to shorter wavelengths compared with those bands in crystals containing only Ag. The optical bleaching experiments on these crystals suggest that colour centres containing both Ca and Ag are probably formed, as in the case of similar crystals electrolytically coloured.
Zur Theorie des Ferromagnetismus magnetisch anisotroper Schichten mit kubischer Kristallstruktur I. Berechnung der Magnetisierung und der Curietemperatur mit der Methode der Greenschen Funktionen
Authors: Brodkorb W. 
Published: July 2007

AbstractEs wird eine ferromagnetische dünne Schicht betrachtet, deren Atomspins S > 1/2 in einem kubischen Gitter mit (100)‐Oberflächenorientierung angeordnet sind. Der Hamiltonoperator des Systems enthält den Zeeman‐, den Austausch‐ und magnetische Anisotropieterme. Es wird ein expliziter Ausdruck für die Magnetisierung angegeben, und dieser Ausdruck wird dazu benutzt, um die ferromagnetische und paramagnetische Curietemperatur zu berechnen. Dabei wird die Methode der Greenschen Funktionen angewendet.
Direct Measurement of the Diffusion Length of Singulet Excitons in Solid Phenanthrene
Authors: Gillus G. , Wolf H. C. 
Published: July 2007

AbstractThe average radial diffusion length of excitons in evaporated layers of solid phenanthrene is measured directly. Assuming surface‐quenching of the excitons, it is found, that r = 263 ± 85 Å.
Symmetry Orbitals and UV Selection Rules for the Polymethylene Chain
Authors: McCubbin W. L. 
Published: July 2007

AbstractBasis functions for irreducible representations of the line group of polymethylene chain are presented. This work confirms the general features of a semi‐quantitative band structure given previously. The UV selection rules are derived and are found to support the earlier conjecture that the transition probability for optical transitions to the first unoccupied band is negligible. It is pointed out that the selection rules may also be used to predict the dichroism of the polymethylene crystal.