bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Mechanism of Heat Transfer in Ag2S and Cu2S
Authors: Okhotin A. S. , Krestovnikov A. N. , Aivazov A. A. , Pushkarskii A. S. 
Published: July 2007

AbstractAn analysis is made of the anomalous temperature dependence of the thermal conductivity of the β‐modifications of the semiconductors Ag2S and Cu2S. The activation model of heat transfer is used for the interpretation of these fluctuations. The calculations confirm that the conclusions are justified.
Photostimulated Electron Emission Spectra of Vacuum‐Ultraviolet‐Irradiated Ionic Crystals
Authors: Bichevin V. , Käämbre H. 
Published: July 2007

AbstractBy the investigation of the spectral characteristics of photostimulated electron emission it has been shown that F‐centres are created in NaCl, KCl, KBr, and KI single crystals by ultraviolet irradiation in the 5 to 11 eV region. The F‐centres are formed as a result of the photoproduction of excitons as well as electron–hole pairs, the exciton mechanism being especially effective. Under stimulation with visible light, electron emission appears from UV‐created F‐centres due to a two‐step photothermal process in crystals with sufficiently low electron affinity χ and by the usual photoemission mechanism in crystals with relatively high χ.
On the Spectra of Impurity Photoconductivity of n‐ and p‐Type Indium Antimonide at Low Temperatures
Authors: Ismailov I. M. , Nasledov D. N. , Smetannikova Yu. S. 
Published: July 2007

AbstractThe spectra of impurity photoconductivity of n‐ and p‐type indium antimonide at 6, 40, and 80 °K are investigated. The oscillations observed in the impurity photoconductivity of p‐type samples at helium temperature result from the interaction of hot holes and longitudinal optical phonons. It is found that the photoexcitation of electrons from the deep donor level to the conduction band in high electric fields leads to oscillatory impurity photoconductivity with periods equal to the limiting energies of the longitudinal and transverse acoustic phonons; the photocurrent value and relative amplitude of the oscillations depend nonlinearly on the electric field. The field dependence of the electron lifetime is evaluated.
On a Specific Mechanism of Absorption of Electromagnetic Waves by Impurity Polarons
Authors: Klinger M. I. , Blakher E. 
Published: July 2007

AbstractA theory is developed for a polarization mechanism of absorption of electromagnetic waves by polarons localized on impurity centres with an appropriate structure. The coefficient of this absorption shows a specific frequency (ω) dependence both at low and at high ω and some basic features (at high ω) similar to those for the high‐frequency conductivity for small polarons and for the well‐known resonance impurity polaron absorption.
ESR Studies of V‐Centres in NaCl (Ca++) Crystals
Authors: Watterich A. , Gécs M. , Voszka R. 
Published: July 2007

AbstractIn OH‐free grown NaCl (Ca++) crystals three paramagnetic V‐centres can be observed under different conditions. Irradiation of the crystals with X‐rays at liquid nitrogen temperature produces VK‐centres, irradiation at dry ice temperature or warming up the VK‐centre causes the V‐centre to appear. At room temperature X‐irradiation leads to a paramagnetic centre which may be considered with high probability to be a VF‐centre.
On the Anisotropic Microwave Conductivity in the Hot‐Electron Region of n‐InSb
Authors: Richter K. , Bonek E. 
Published: July 2007

AbstractIt is shown by experiment that the small‐signal microwave conductivity of n‐type InSb at 77 °K and 35 GHz decreases considerably, when an electric de field in excess of 10 V/cm is applied simultaneously. Further, a marked anisotropy with respect to the direction of the applied de field is observed. A sample with higher electron mobility shows a stronger anisotropy than a sample with lower mobility. It is possible to measure the momentum relaxation time because of the occurrence of strong relaxation effects. The microwave conductivity, which is dominated by these effects, can be calculated by assuming mean momentum and energy relaxation times according to Kopetz and Pötzl. The applicability of these relaxation times to the hot‐electron region of InSb is proved by the good agreement between experimental and theoretical results.
Antiphase Boundaries and Twins Associated with Ordering of Indium Vacancies in β‐In2S3
Authors: van Landuyt J. , Amelinckx S. 
Published: July 2007

Abstractβ‐Indium sulfide crystals have been studied by electron microscopy and electron diffraction. From an analysis of the defective spinel structure, different types of ordering defects are predicted. Ordering twins and two types of antiphase domains have been observed, and their analysis is in complete agreement with the proposed models. Heating experiments enabled a distinction to be made between the defects associated with the tetrahedrally surrounded cations and those in octahedral sites. A mechanism is proposed for the two transitions previously observed in this material: The transition at 420 °C is attributed to the disordering of tetrahedral cations, whereas the transition at 750 °C is associated with the disordering of the octahedrally surrounded cations.
Photographs of the Diffraction Pattern of Ferromagnetic CrBr3
Authors: Fischer F. 
Published: July 2007

AbstractSharp diffraction patterns of the Fresnel type, which are free from distortion, have been photographed using monochromatic light and fixing the crystal to a 50 μm hole diaphragm cooled to 20 °K in an optical cryostat. Temporary saturation of the magnetization gives three different types of patterns according as the magnetic field forms an angle of 90, 45, or 0° with the crystal c‐axis. Linearly polarized light gives interference spots of the first order polarized perpendicular to the primary light. An interpretation is presented considering also the circular dichroism. Second‐order spots polarized parallel to the primary light are probably due to the domain walls. Above an activation temperature of TA = 31.5 °K the domain walls become mobile. Hereby the 90° and the 45° type change into the 0° type. The latter also appears after cooling from above TC.
Electrical Breakdown in Germanium Exposed to Infra‐Red Radiation
Authors: Brandt E. H. , Güth W. 
Published: July 2007

AbstractInfra‐red irradiation accelerates the build‐up of an avalanche in weakly n‐doped Ge and increases the steady‐state current. Both effects occur even if the photo‐current is very small at the beginning of the avalanche or at fields below the threshold of a breakdown. The dependence on the wavelength of the breakdown current has been measured and the time dependence of the avalanche rise investigated. An explanation of the effect of the radiation has been offered.
Dirt in Slater's Split‐Band Model of Antiferromagnetism
Authors: Johansson B. , Berggren K.‐F. 
Published: July 2007

AbstractThe effect of impurities on the split‐band model is analysed. As in the case of a dirty superconductor and a dirty excitonic state gaplessness is found for a certain range of impurity concentration. Implications on transition‐metal oxides (and sulphides) are briefly discussed.
Ellipticity of π/2‐Spin Waves for Cubic Crystals
Authors: Voigt F. 
Published: July 2007

AbstractThe ellipticity of a spin wave dependences on the dipole‐dipole‐interaction and the crystalline anisotropy energy. It will be shown that when only magnons having a single wave vector are excited in the parallel‐pumping experiment the ellipticity may be estimate from the dc magnetic fields for the minimum of the butterfly‐curve at the [100]‐ and [111]‐magnetization direction. Only the magnetization and the gyromagnetic factor must be known from other measurements, not the constants of the crystalline anisotropy energy.
The Fine Structure of Spots in Electron Diffraction Resulting from the Presence of Planar Interfaces and Dislocations V. Multiple Beam Case
Authors: Gevers R. , Serneels R. , van Landuyt J. , Amelinckx S. 
Published: July 2007

AbstractA description is given of the fine structure of the electron beams transmitted and scattered by a plate‐shaped foil containing a stacking fault or an anti‐phase boundary inclined with respect to the surface. It is assumed that there are n strong diffracted beams. The transmitted and each strong scattered beam consists of n (n + 1) + 1 beams, very slightly different in orientation, and which give rise to the appearance of satellites of the diffraction spots. The geometry and the intensities of the satellite configurations are discussed. General properties can be derived from the formulation developed in the paper. Electrons leaving the crystal in a satellite beam direction are those which have changed from one wave field to another on crossing the fault boundary. The influence of the anomalous absorption, important for a thick crystal, is also examined. Satellite beams formed by electrons moving in a strongly absorbed wave field before or (and) after crossing the stacking fault, will be weak. A bright satellite is expected if one or both of these fields are easily transmitted. Finally it is shown that the intensities of the different satellite beams are not the same in different parts of the faulted region.
Investigation of Dynamic Characteristics of Ferromagnetics at Low Temperatures
Authors: Škrinjar M. J. , Tošić B. S. 
Published: July 2007

AbstractThe low‐temperature characteristics of ferromagnetics with the effective spin S = 1/2 are investigated using the exact Bose representation of spin operators. The main result of the investigation is that due to anharmonic effects in the magnon system the Bloch's formula for magnetization has a correction which is proportional to the square of the temperature.
Initial Susceptibility of Ferrimagnetic Materials and Topography of Domain Walls
Authors: Globus A. , Duplex P. 
Published: July 2007

AbstractObservations are reported, that ferrimagnetic materials which are identical in their fundamental properties (composition, Ms, Tc, λs) as well as in their granular structure (porosity, size, and shape of grains) can present very different thermal spectra of initial susceptibility. This behaviour is found to be general for the many compositions studied. The proposed interpretation is based on the existence of different degrees of wall continuity accross the grain boundaries. It is suggested that the degree of wall continuity is associated with the relative crystallographic axes orientation of the grains. The experimental results of the frequency spectra of intial susceptibility support this hypothesis. It is also observed that the hysteresis of thermal spectra is quite general and this in turn can be related to the wall topography.
Electromigration in Liquid NaK Alloys
Authors: Jousset J. C. , Huntington H. B. 
Published: July 2007

AbstractThe relative electromigration of Na and K atoms in liquid NaK alloys has been investigated for two compositions, 0.47 and 0.30 K (atom. conc.). This effect has been found to be in the opposite direction for the two alloys; Na ions go towards the anode for the 0.47 K concentration and towards the cathode for the 0.30 K. The interpolated concentration of this reversal is found to equal 0.39 K, in agreement with the result of Drakin and Maltsev [13]. The variation of the coefficients of “electron drag” for both components has been measured as a function of temperature in the range of 85 to 300 °C, where they behave anomalously. In both the dilute and concentrated alloy regions the directions of the mass flux agree with theoretical predictions but the magnitudes are smaller by nearly a factor of 10. A possible explanation may be that mass transport proceeds through the motion of large coordinated complexes. The breakup of these complexes at higher temperature might explain one aspect of the anomalous temperature dependence.
Field Emission from p‐Type Si
Authors: Fursey G. N. , Egorov N. V. 
Published: July 2007

AbstractThe nonlinear field emission behaviour in dependence on temperature and light intensity was studied in p‐type silicon crystals, whose surfaces were prepared by high‐field evaporation in vacuo. The voltage drop along the emitter measured by the retarding potential technique and the size of the emission pattern were determined for every point of the Fowler‐Nordheim plot. The curvature of the current—voltage curves for Si has more distinct character than it was observed earlier for Ge. The region of “absolute field emission saturation”, which extends over a wide range of applied voltage variation was found in the Fowler‐Nordheim plots. The emission current—voltage behaviour appreciably depends on sample history and especially on temperature treatments. Sample heating to 400 to 450 °C during bake‐out fully distorts the field emission data in Si. Light and temperature produce the same effect on the field emission current.
Wasserstoff in Metallen als Beispiel für ein Gittergas mit Phasenumwandlungen
Authors: Alefeld G. 
Published: July 2007

AbstractAus Phasendiagrammen und Löslichkeitsmessungen für Wasserstoff in Metallen kann gefolgert werden, daß es in dem von der Metallmatrix aufgespannten Raume für den interstitiell gelösten Wasserstoff — analog zu freiem Wasserstoff — die Phasenumwandlung gasförmig‐flüssig gibt. Der kritische Punkt der Mischungslücke wird mit dem kritischen Punkt für die Phasenumwandlung gasförmig‐flüssig identifiziert. Aus Löslichkeitsmessungen lassen sich die Zustandsdiagramme für das Gittergas bestimmen. Diese zeigen den für ein nichtideales Gas charakteristischen Verlauf, einschließlich des kritischen Punktes und des durch die Koexistenzkurve begrenzten Zweiphasengebietes. Auch die Diffusions‐konstante des gelösten Wasserstoffs, die den für Festkörpersysteme bei Raumtemperatur üblichen Wert um etwa 10 Größenordnungen überschreitet, ist vergleichbar mit der in freien Flüssigkeiten. Wasserstoff in Metallen kann also in erster Näherung als ein Beispiel für das theoretisch untersuchte Gittergas mit seiner Phasenumwandlung zur Flüssigkeit angesehen werden.
The Chemical and Isoconcentration Diffusion of Zn in AlSb
Authors: Showan S. R. , Shaw D. 
Published: July 2007

AbstractThe chemical diffusion of Zn in AlSb has been investigated as a function of temperature in the range 650 to 933 °C and as a function of Zn surface concentration. The diffusion coefficient is found to be concentration‐dependent and shows a behaviour similar to that observed in GaAs, GaP, and InP. Isoconcentration diffusion of Zn at 933 °C in AlSb is found to be strongly concentration‐dependent. Quenching of Zn‐diffused samples shows that the substitutional Zn is a single‐level acceptor which is completely ionized at the diffusion temperature. It is concluded that the Longini model provides a satisfactory interpretation of the diffusion processes. Substitutional Zn in AlSb is also found to show retrograde solubility.
Infrared Measurements on CdS Thin Films Deposited on Aluminium
Authors: Proix F. , Balkanski M. 
Published: July 2007

AbstractThe reflectivity spectra of three CdS thin films (thickness 0.086, 0.33, and 0.66 μm) deposited on aluminium have been determined at room temperature. The measurements were carried out in the spectral range 180 to 740 cm−1, at an incidence of 45°, for light polarized with the electric field in the plane of incidence. A small absorption peak is observed near ωTO for the thicker samples, and a much stronger absorption peak near ωLO for all samples. The results are analysed in terms of the theory of Fuchs and Kliewer. The frequencies of the peaks and the partial widths associated with the virtual modes are in very good agreement with the theory. It is also found that the anharmonic width of the peaks is much larger than in CdS single crystals.
The Complete Dependence on Crystal Orientation of the Hall Coefficient of Copper
Authors: Saeger K. E. , Lück R. 
Published: July 2007

AbstractA technique has been developed for measuring the Hall coefficient which is based on the invariance of the antisymmetric part of the resistivity tensor with respect to rotational transformation. This technique permits the Hall coefficient for any orientation to be determined on one single crystal. In this paper it has been applied to copper. The results thus obtained are used for the calculation of the Hall conductivity which, in turn, yields information on characteristic properties of the Fermi surface.
Electrical Switching Phenomena in Transition Metal Glasses under the Influence of High Electric Fields
Authors: Drake C. F. , Scanlan I. F. , Engel A. 
Published: July 2007

AbstractA mechanism is proposed to account for the phenomena observed in many vitreous systems of field‐induced switching between two or more conducting states. Conduction in the high resistance state is assumed to involve electron hopping between non‐identical sites. The vitreous nature of the systems precludes extrinsic conduction, and the equilibrium number of intrinsic carriers is shown to be a function of the degree of inequality of site configurations, temperature, field strength, and dielectric constant. The carrier mobility is a function of averaged distance between sites, of temperature, and dielectric constant. Dc conduction and dipole production and orientation are shown to be interrelated processes. The consequent non‐linear dependence of polarization on field leads to a quasi‐ferroelectric reorganization of the structure at a critical field strength. The structural reorganization makes the site environments more nearly identical, and thereby delocalizes the excess electrons on one of the sites producing semi‐metallic conduction. Local energy dissipation by the turn‐off pulse raises the lattice temperature sufficiently to allow the structure to relax to its initial state. The quantitative implications of the theory are developed, and compared with measurements on some copper glasses.
Some Numerical Results on Quasiparticle Properties in the Electron Gas
Authors: Lundqvist B. I. 
Published: July 2007

AbstractNumerical results for some quasiparticle properties of an interacting electron gas are presented. New data are given for highly excited electrons. It is shown that there is a characteristic momentum dependence in the energy, damping rate, and spectral weight of the quasiparticle. The results are calculated using a self‐energy expression to the lowest order in the effective (RPA) interaction between the electrons. Well‐defined peaks in the spectrum are obtained for all momenta, and in this sense it is concluded that the quasiparticles have a physical meaning everywhere in momentum space.
Electroabsorption of CdS and CdSe Single Crystals in the Exciton Region
Authors: Lange H. , Gutsche E. 
Published: July 2007

AbstractElectroabsorption spectra in the exciton region were measured on very thin CdS and CdSe single crystals at 77 °K in the field range 1 × 103 to 2.4 × 104 V/cm for both polarizations of incident light with respect to the c‐axis. The electroabsorption spectra exhibit much more details than electroreflection spectra know so far. The variation of peak positions and peak heights with electric field strength is different for different parts of the spectrum. Some of the peaks shift to lower and others o higher energies with increasing field strength. The spectra can be interpreted in terms of a second order Stark shift, field induced line broadening and Franz‐Keldysh type interband oscillations.
The Work Function in Simple Metals
Authors: Schneider T. 
Published: July 2007

AbstractWe have applied the pseudopotential approach for a calculation of the work function for simple metals. The alkali metals, magnesium, and aluminium are treated quantitatively, using a model‐pseudopotential determined from the measured phonon dispersions or the elastic constants. Our results indicate that the correlation energy contributes significantly to the work‐function. Generally, good agreement is achieved.
Contribution of the Piezoelectric Scattering to the Energy Scattering of Conduction Electrons in Semiconductor Thin Films
Authors: Ilkovič V. 
Published: July 2007

AbstractThe parameter β characterizing the interaction between the conduction electrons and the lattice is calculated for a thin film of non‐degenerate semiconductors using the electrontemperature approximation taking into account the scattering by the deformation and the piezoelectric potential. It is shown that the energy scattering of the conduction electrons on the piezoelectric potential in thin films of n‐InSb is important in the temperature region below 10 °K.
A Field ion Microscope Investigation of 10 MeV Proton Damage in Iridium
Authors: Petroff P. , Washburn J. 
Published: July 2007

AbstractAnnealed iridium specimens of 99.99% purity were irradiated at 5 °K with 10 meV protons in a field ion microscope attached to a cyclotron. Contrast effects due to point defects and their clusters were analyzed. By a field evaporation technique the point defect distribution in the bulk was investigated. Interstitial migration to the surface was directly observed upon annealing in the temperature range 15 to 42 °K. The decrease in the bulk concentration of interstitials during annealing in the temperature range 5 to 300 °K indicated that stage I is caused by interstitial migration to close‐by vacancies and traps and stage II was due to interstitial detrapping. Damage caused by irradiation at 5 °K was compared to that introduced at 300 °K. The damage which was large voids (400 to 500 vacancies) and dislocation loops suggested a different formation mechanism in the specimens irradiated at higher temperature.
Elastic Constants of the Fluxoid Lattice Near the Upper Critical Field
Authors: Labusch R. 
Published: July 2007

AbstractThe elastic constants of the fluxoid lattice are calculated in terms of the reversible magnetisation curve by taking the appropriate derivatives of the free energy of the fluxoid assembly. The expressions obtained in previous work for the compressional modulus and for the shear modulus c44 in magnetic fields well below Hc2 are confirmed and their validity over the entire range of field between Hc1 and Hc2 is established. A new expression is derived for the shear modulus c66 in high fields. It turns out that c66 goes quadratically to zero if the applied field approaches Hc2.
The Mechanical Behaviour of an Iron—11 at% Molybdenum Alloy in the Temperature Range 295 to 1100 °K
Authors: Rawlings R. D. , Newey C. W. A. 
Published: July 2007

AbstractThe effect of precipitation of an intermetallic compound on the mechanical behaviour of an Fe—11 at% Mo alloy has been studied by means of compression tests in the temperature range 295 to 1100 °K. At temperature up to 700 °K for the well‐aged conditions of the alloy and 875 °K for the solution‐treated and slightly aged states, the temperature dependence of the yield and 0.2% proof stresses can be accounted for by the change in the elastic modulus with temperature. For the well‐aged conditions in the temperature range 700 to 950 °K the yield strength was temperature and strain‐rate sensitive. It is concluded that in this temperature range, deformation is determined by the diffusion‐controlled motion of dislocations past the precipitate barriers. Above about 950 °K all conditions of the alloy exhibited a similar, and large, temperature dependence of the yield strength; in addition, secondary creep occurred at the imposed strain rate and the creep stress was found to be independent of the size and distribution of the precipitate. The very high values of the apparent activation energy for yield and secondary creep found above 950 °K are considered to be due to an anomalous change in the activation energy for diffusion during the Curie transformation.
Point Defects in Ferromagnetic Thin Films
Authors: Sukiennicki A. , Zagórski A. 
Published: July 2007

AbstractThe effect of point defects (vacancies, magnetic impurities) on the spontaneous magnetization of thin films is computed in the molecular field approximation. It is found that the magnetization distribution around the defects is not spherically symmetric as in the case of the bulk materials; it is modified by the film surface. The results may be applied generally to all surfaces of bulk materials.