bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Possibility of Existence of Quantum Electromagnetic Waves in Metals
Authors: Kaner E. A. , Skobov V. G. 
Published: July 2007

AbstractThe electromagnetic properties of a metal are considered theoretically for strong quantization of the electron states in a magnetic field. It is shown that a large number of quantum waves should occur with velocities close to the discrete velocities of the electrons on the Fermi surface. The extensce of these waves is due to the absence of Landau damping in the interval between giant oscillation maxima.
Stacking Faults in a Non‐Stoichiometric Face‐Centred Cubic TaC
Authors: Martin J. L. , Jouffrey B. , Costa P. 
Published: July 2007

AbstractStacking faults are observed by transmission electron microscopy in face centred cubic TaC0.75. These stacking faults have the same contrast as intrinsic faults in face centred cubic metals; they do not exist in nearly stoichiometric carbides. No metallic plane relaxation is detected in the neighbourhood of a fault. It seems that another carbide phase precipitates along the fault planes in a Widmanstätten structure.
Surface Spin Waves in Hexagonal Cobalt Thin Films
Authors: Puszkarski H. 
Published: July 2007

AbstractIt is shown that excitation of acoustic surface spin waves is possible for certain intervalls of the parameter A which describes the degree of spin pinning. The resonance absorption obeys the k−1 rule. The first resonance spin‐wave mode, weaker than the next one, is expected to have a surface spin‐wave nature.
Effects of Fast Neutrons on Electric Properties of NiO Single Crystals
Authors: Cojocaru L. N. 
Published: July 2007

AbstractA study is made of the effect of fast neutrons on the electric conductivity and thermo‐electric power of NiO single crystals. It is found that the conductivity and thermo‐electric power are reduced after an irradiation of about 1017 nvt. This is explained by assuming that the defects introduced into the NiO lattices act as acceptors and not as trapping centres for holes. The decrease of the electric conductivity is due to the mobility decrease whilst the decrease in the thermo‐electric power arises from the increase of the hole concentration.
On Energy Bands of Crystals with Lowered Point Symmetry
Authors: Frei V. 
Published: July 2007

AbstractThe special case of those subgroups of space groups that have the same translational symmetry but lowered point symmetry is discussed from the crystallographic, group‐theoretical and physical points of view. Consequences are studied concerning the energy band structure (degeneracies, zero slopes of E(k), dipole selection rules, etc.). It is shown preliminarily that the theory of space subgroups [3] is important here and that the case of lowered point symmetry is especially simple and physically interesting.
Calculation of Light‐Stimulated Luminescence and Current Transients in Phosphors. (Release of Trapped Carriers by Light)
Authors: Bráunlich P. 
Published: July 2007

AbstractThe paper discusses light‐stimulated luminescence and conductivity in phosphors using a model proposed by Schön [1]. This model was previously used for the calculation of thermoluminescence on thermally stimulated current [2]. It considers transitions between defect levels and both bands (conduction band and valence band) and is, therefore, suited for the calculation of light‐stimulated recombination phenomena in phosphors in cases where the energy distribution of light allows a simultaneous release of trapped carriers from electron and hole traps. Approximate solutions are presented. In one case the approximate solutions are compared with numerical solutions of the rate equations which govern the recombination kinetics. A method for the determination of the cross‐section of hole traps for light absorption is discussed.
A Thermodynamic Investigation of the Conditions for the Generation of Oscillations of an Electric Current Flowing through a Non‐Ohmic Medium
Authors: Pastrňák J. 
Published: July 2007

AbstractPrevious experimental and theoretical work on instabilities of the electric current have been mostly limited to various special cases. A better approach would be to treat the problem generally in terms of phenomenological non‐equilibrium thermodynamics. This would lead to some general conclusions which would be independent of the microphysical origin of the instabilities. It is shown here that even the restricted approach of taking the electric field as the thermodynamic force yields some general results of this nature which provide new information on this problem.
Spontaneous Recombination of Frenkel Pairs in Neutron‐Irradiated Solids
Authors: Dettmann K. , Leibfried G. , Schroeder K. 
Published: July 2007

AbstractThe accumulation of Frenkel defects in neutron‐irradiated solids is studied using a simple model of a displacement cascade. The lowering of the damage rate by spontaneous recombination of unstable Frenkel pairs is taken into account. The general equations are solved using the superposition approximation in which third‐order correlations are replaced by products of second‐order correlations. The saturation density of defects and the damage rate as a function of the density are calculated. By comparison with experiment the annealing and cascade volumes can be deduced for various metals.
Electrical and Optical Properties of Titanium‐Doped Lithium Fluoride Crystals
Authors: Jain S. C. , Sootha G. D. 
Published: July 2007

AbstractMeasurements are made of the electrical conductivity and optical absorption of LiF crystals doped with Ti. The plot of log (σ T) as a function of 1/T shows the usual intrinsic and extrinsic regions. In the extrinsic region, the behaviour of titanium is found to be similar to that of magnesium but different from that of manganese. The results indicate that most of the titanium is present in a highly aggregated form. However, a small fraction of the titanium is atomically dispersed in the form of doubly positively charged centres, either as Ti2+ or as stable pairs of Ti3+ and a cation vacancy. The values of the energies derived from the conductivity plot are W = 2.74 eV for the energy of formation of a separated pair of vacancies, E = 0.70 eV for the activation energy for the migration of a cation vacancy, and Wa = 0.48 eV for the energy of association of a cation vacancy with a titanium centre. Unirradiated LiF:Ti crystals show an optical absorption band, designated as the E‐band, at 207 nm with a half‐width of 0.72 eV. On X‐irradiation, this band decreases, and the F‐band and two new bands are observed. The new bands are designated as the H‐ and G‐bands. The H‐band occurs at 240 nm with a half‐width of 0.20 eV and the G‐band at 270 nm with a half‐width of 0.25 eV. The rate of growth of the F‐band on X‐irradiation is enhanced considerably by titanium impurity. Possible models of the E‐, G‐ and H‐centres are discussed and approximate values of the appropriate oscillator strengths are: fF = 0.32, fE = 0.23, and fG = 0.07. Attempts to distinguish between Ti2+, and Ti3+ plus a cation vacancy, by ESR absorption measurements are not successful because the titanium in highly aggregated form gives a very strong, complicated, and temperature independent background to the ESR absorption. Experiments are suggested which would distinguish between the two possible models of the titanium centres.
Epitaxial Growth of Vacuum‐Evaporated Co on NaCl. I. Conditions Leading to Epitaxy
Authors: Otsuka K. , Wayman C. M. 
Published: July 2007

AbstractConditions necessary for complete epitaxial growth ((001) [100] Co // (001) [100] NaCl) of f.c.c. Co on NaCl were investigated. Both high‐evaporation rates and vacuum cleavage were found necessary, which indicates the importance of substrate cleanliness. It also appears necessary to avoid the nucleation of h.c.p. Co in order to obtain epitaxial growth of the f.c.c. phase. The development of “abnormal” h.c.p. crystals of Co in fiber texture orientation (00.1) h.c.p. // (001) Nacl is discussed. It is suggested that contaminants aid the occurrence of h.c.p. Co in preference to the f.c.c. form.
The Structure of Silicon Oxide Films
Authors: Coleman M. V. , Thomas D. J. D. 
Published: July 2007

AbstractThe scattering of electron waves by an amorphous material is partly dependent on its structure. The variation of this scattered intensity with angle may be mathematically transformed to give a radial distribution function (r.d.f.) which describes both the position and co‐ordination of sets of atoms. The methods used to obtain the r.d.f. from the structurally dependent intensity and the elimination of errors are described. To determine the scattered intensity experimentally, the electron diffraction pattern is scanned across a small aperture and the open circuit voltage developed in a silicon solar cell is measured. The structure found for amorphous silica films is similar to that determined by X‐rays and amorphous silicon has the expected tetrahedral bonding. It is shown that glow discharge and evaporated silicon oxide films, whose average composition lies between silicon and silica, consist of a mixture of these latter two materials.
Mössbauer Study of β‐ and δ‐FeOOH and their Disintegration Products
Authors: Dézsi I. , Keszthelyi L. , Kulgawczuk D. , McInár B. , Eissa N. A. 
Published: July 2007

Abstractβ‐FeOOH and δ‐FeOOH are studied by Mössbauer effect measurements. The Néel point of β‐FeOOH is TN = (295 ± 4) °K. Above this temperature the material is paramagnetic with quadrupole splitting and it decomposes to α‐Fe2O3 at 670 °K. The transition at this temperature takes 12 hours. The two internal magnetic fields observed in δ‐FeOOH are found to correspond to Fe3+ ions in octahedral and tetrahedral positions. δ‐FeOOH decomposes to intermediate products at 370 °K below its Curie Temperature and it disintegrates to α‐Fe2O3 at approximately 510 °K.
Das Erholungsspektrum von Kobalt
Authors: Bilger H. , Kronmüller H. 
Published: July 2007

AbstractAn plastisch verformten Kobalt‐Einkristallen wurden Erholungsmessungen des elektrischen Widerstandes im Temperaturbereich zwischen 4 und 550 °K durchgeführt. Ein Vergleich dieser Messungen mit Ergebnissen anderer Autoren ermöglicht eine vorläufige Deutung des Erholungsverhalten von Kobalt. Es zeigt sich dabei, daß zwischen dem Erholungsverhalten des hexagonalen Kobalts und der kubisch‐flächenzentrierten Metalle eine weitgehende Analogie besteht. Unter anderem wird die Stufe II in Kobalt der Annihilation weit entfernter Frenkelpaare, Stufe III der Annihilation freier Zwischengitteratome an Leerstellen und Stufe IV der Wanderung von Leerstellen zugeschrieben. Die Experimente weisen ferner darauf hin, daß im Temperaturbereich der Stufe III auch die Wanderung von Doppelleerstellen eine Rolle spielen kann.
Der Einfluß der Magnetostriktion auf die magnetische Bereichsstruktur einachsiger Kristalle, insbesondere des Kobalts
Authors: Hubert A. 
Published: July 2007

AbstractDie Bereichsstrukturen, die auf der Basisebene eines Kobalteinkristalls auftreten, wurden experimentell und theoretisch untersucht. Die Vielfalt der Erscheinungen läßt sich deuten, wenn man zu den bisher betrachteten Energietermen noch die magnetostriktive Eigenenergie hinzunimmt. Diese Energie beherrscht vor allem die Strukturen in dickeren Kristallen (> 10 μ m) und in höheren Magnetfeldern. Die Bereichsstrukturen dünnerer Kristalle werden zwar primär von der Wandenergie bestimmt, doch spielt auch hier die magnetostriktive Energie noch eine bedeutsame Rolle, vor allem für die Keimbildung in hohen Feldern. So muß das sog. Wabenmuster in dünneren Kristallen nach unseren Ergebnissen neu interpretiert werden. Auf Anwendungsmöglichkeiten zur Untersuchung plastisch verformter Metalle wird hingewiesen.
Non‐Equilibrium Vacancy Concentrations in Metals Subject to Thermal Gradients and Electric Fields
Authors: Blackburn D. A. 
Published: July 2007

AbstractGradients of temperature and electric fields may be used to cause vacancy currents in metals. If vacancies are supposed to migrate between randomly distributed, fixed sources and sinks, a metal subject to an internal electric field E, parallel to a temperature gradient ∂T/∂x, should suffer a vacancy supersaturation given by q = Ce r Lambda;2/k2 T4 [(Ef(Ef + Em + Et ‐ 2 kT) + Et (Em ‐ 2 kT)) (∂T/∂x)2 ‐ Z e E T (Ef + Em ‐ kT) ∂T/∂x ‐ Z e kT3 ∂E/∂x + Et kT2 ∂2T/∂x2], where Ce denotes the equilibrium vacancy concentration appropriate to the temperature T at any point x, and Lambda; is the mean free path of a vacancy during migration between source and sink. Ef, Em, and Et are the energies for formation, motion, and transport of vacancies, Z e is the effective electrical charge carried by a vacancy when diffusing, and r is a geometrical constant (1/6 in f.c.c.).
Absorption of Ultrasound in Indium Antimonide
Authors: Hrivnák L. , Kovár J. 
Published: July 2007

AbstractThe frequency dependence of the attenuation coefficient for longitudinal ultrasonic waves in InSb is determined over the range 50 to 210 MHz for temperatures between 200 and 600 °K. The experimental results are interpreted using the Woodruff‐Ehrenreich theory. It is shown that above 200 °K the attenuation coefficient decreases with increasing temperature according to the function A/(1 + β T) and therefore the lattice thermal conductivity decreases as the function B/T (1 + β T), in accordance with theories of lattice thermal conductivity.
Mössbauer Spectra in the Presence of Electron Spin Relaxation (I)
Authors: Gabriel H. 
Published: July 2007

AbstractThe effect of time‐fluctuating electronic spins (magnetic fields) on the hyperfine splitting of the Mössbauer spectra is investigated. The author's previous formal theory, which utilizes the Liouville formalism due to Zwanzig, is briefly outlined and extended by considering relaxation effects in more detail. The solution for large times involves a superposition of frequency‐shifted Lorentzian lines with modified line widths. The frequency shift and the change in line width are obtained as functions of the nuclear spins, the magnetic quantum numbers, the magnetic moments, and of correlation functions defined in terms of the fluctuating spins.
Rubans d' aimantation dans les lames minces de fer pur
Authors: Bourret A. , Kleman M. 
Published: July 2007

AbstractLe modèlé de répartition de l'aimantation dans les domaines en rubans (stripe domains) des lames minces de fer monocristallines d'orientation (111), est ici repris et appliqué è la géométrie particulière de la lame. Les équations linéarisées ainsi obtenues donnent une expression algébrique des composantes de l'aimantation dans la lame. Celles‐ci sont ensuite utilisées pour le calcul des divers contrastes de diffraction attendus, par résolution des équations de Howie et Whelan dans l'approximation á 2 ondes. Ces contrastes sont en bon accord avec les résultats expérimentaux.
Autodiffusion au joint de grains de bicristaux d'argent soumis à une pression hydrostatique
Authors: Martin G. , Blackburn D. A. , Adda Y. 
Published: July 2007

AbstractL'autodiffusion au joint de grains de bicristaux d'argent à forte désorientation a été mesurée sous des pressions hydrostatiques comprises entre 0 et 8 kbar. On observe une variation de vitesse de diffusion correspondant à un volume d'activation de (11,5 ± 2,5 cm3/g‐at) soit (1,1 ± 0,2) fois le volume atomique.
Anisotropy of Thermomagnetic Effects in n‐Ge
Authors: Samoilovich A. G. , Buda I. S. , Dakhovskii I. V. 
Published: July 2007

AbstractA generalization of the theory of the anisotropic scattering of current carriers is proposed for the case of a phonon‐drag effect. For two selected versions of phonon‐phonon scattering theory it is possible to determine the nonequilibrium partition‐function of the phonons. Calculations are made of the longitudinal and transverse Nernst‐Ettinghausen effects in n‐Ge on the basis of anisotropic scattering and a phonon‐drag effect. The results are compared with experimental data [1], and it is found that the present theory agrees well with experiment.
Spectral Response of p‐n Heterojunctions
Authors: Tansley T. L. 
Published: July 2007

AbstractSemiconductor heterojunctions have been grown by the deposition of III‐V solid solutions on GaAs substrates and their optical properties studied in detail. While the general picture is that deduced from simple theory, some interesting second order phenomena have been observed. Effects considered include absorption in the wide gap material, loss of photocurrent due to the conduction band spike and notch and high field absorption effects in the narrow gap material transition region. Experimental results are presented and the incidence of these effects in real heterojunctions discussed.
Optical Measurement of Compensation in Highly Doped Silicon
Authors: à la Guillaume C. Benoit , Voos M. 
Published: July 2007

AbstractThe radiative recombination spectrum of silicon which is highly doped with 7 × 1018 cm−3 Sb atoms is analysed between 4.2 and 110 °K. From these measurements, it can be deduced that the silicon is compensated, and it is also possible to determine the nature of the compensating impurity. It is shown that the compensating impurity concentration can be obtained from the Shockley‐Read theory which allows a calculation to be made of the ratio of the hole and electron capture probabilities for such a recombination centre.
Energy Band Structures of Cubic ZnS, ZnSe, ZnTe, and CdTe (Korringa‐Kohn‐Rostoker Method)
Authors: Eckelt P. 
Published: July 2007

AbstractThe energy band structures of cubic ZnS, ZnSe, ZnTe, and CdTe are calculated by the KKR (Korringa‐Kohn‐Rostoker)‐method. The “muffin‐tin” potential, on which the calculations are based, is described in detail. The calculated energy splittings at critical points are compared with data from optical measurements.
Thermoluminescence Investigations on Doped Alkaline Earth Fluorides
Authors: Görlich P. , Karras H. , Kötitz G. , Ullmann P. 
Published: July 2007

AbstractThe thermoluminescence spectra and glow curves of MeF2: Y, MeF2: Tm (Me:Ca, Sr, Ba), and CaF2: Sm single crystals are measured over the temperature region from 89 to 300 °K and compared with earlier results obtained above room temperature. It is established that temperature has a considerable effect on the spectral intensity distribution of the thermoluminescence emission and effects are observed which arise from both the activator concentration and a charge compensation by NaF. A brief discussion is given of the results.
On Lindemann's Melting Criterion
Authors: Pal S. , Sharma P. K. 
Published: July 2007

AbstractThe ratio ηm of the mean square amplitude of thermal vibration to the square of the interatomic spacing at the melting point are calculated for a number of cubic metals using de Launay's electron gas model. The computation uses Blackmann's sampling technique. In contrast to Lindemann's hypothesis of constant ηm for all solids, the calculated ηm varies widely from one group of the periodic table to another.
Dynamical Scattering Theory for Crystals with Point Defects
Authors: Dederichs P. H. 
Published: July 2007

AbstractDynamic scattering theory is generalized to crystals containing statistically distributed point defects. Various absorption mechanisms are discussed, 1. inner shell absorption modified by a generalized Debye‐Waller factor and, 2. several corrections to this arising from correlations of static and thermal atomic displacements, due to fluctuations of the atomic scattering factors at the lattice points and due to defect clustering.
Growth and Optical Properties of Wurtzite and Sphalerite CdSe Epitaxial Thin Films
Authors: Ludeke R. , Paul W. 
Published: July 2007

AbstractGrowth of epitaxial thin films of sphalerite and wurtzite CdSe on cleaved BaF2 substrates is reported. Optical transmission measurements to 6.5 eV in the ultraviolet at 300 and 80 °K were made. The spin‐orbit splitting of the A3‐;A1 transitions in cubic CdSe is 0.26 eV, in close agreement with seemingly spin‐orbit split transitions of 0.28 eV in the hexagonal phase, attributed to transitions along the Δ‐axis (the c‐axis of the hexagonal Brillouin zone). Our findings substantiate this identification. Other optical structure is reinterpreted based on our measurements and some recent band calculations of wurtzite compounds. A band structure for wurtzite CdSe is proposed.
Effect of Storage Temperature on the Time Dependence of Charge Density in Carnauba Wax and Methyl Polymethacrylate Electrets
Authors: Hilczer B. , Blaszczyk B. , Goderska S. 
Published: July 2007

AbstractAn investigation is made of the effect of storage temperature on the transition time for the heterocharge to homocharge transition in electrets of Carnauba wax and methyl polymethacrylate. The transition time is found to decrease as the temperature is raised. The transition time is also strongly dependent on the electric field strength applied during polarization and decreases as the field strength is increased.
The Reflection Coefficient of Optically Inhomogeneous Solids
Authors: Subashiev V. K. , Kukharskii A. A. 
Published: July 2007

AbstractThe optical reflectivity of some optically inhomogeneous solids is considered and the appropriate general reflectivity formulae are determined. Some particular cases of these formulae are also discussed. The infrared reflectivity spectra of epitaxial and diffused semiconductor layers are calculated as examples.
Nucleation of Zinc Crystals in Multilayer Adsorption
Authors: Gretz R. D. 
Published: July 2007

AbstractThe adpopulation of zinc which is critical for an appreciable nucleation rate of crystallites on clean tungsten field emitter tips has been measured. This critical adconcentration is 2.7 monolayers for zinc, independent of temperature from 75 °K to above room temperature. This phenomena can be described by none of the existing theories of heterogeneous nucleation because all of these theories presuppose that adsorption prior to nucleation is less than a monolayer. For concentrations greater than a monolayer, the exact supersaturation at the substrate becomes indeterminate.
Visualization of Dislocations on Basal Planes of GaSe Single Crystals
Authors: Guseinov G. D. , Ramazanzade A. M. 
Published: July 2007

AbstractScrew and linear dislocations are investigated on the (0001) planes of GaSe crystals. From the measured parameters of the regular growth spirals, calculations are made of the critical nuclear radius, the supersaturation, and the step translation rate. An optimum chemical etching solution (1 HF + 2 HNO3 + 7 HCl) for the (0001) plane of GaSe crystals is established. The density of screw and linear dislocations is determined. The statistical density of screw dislocations is found to be less than 104 cm−2, whilst the density of linear dislocations varies from 2.3 × 105 to 1.3 × 106 cm−2 depending on the mode of rotation.
Étude d'eutectiques supraconducteurs plomb‐étain à lamelles orientées
Authors: Dobrosavljevic L. , Dupuis C. 
Published: July 2007

AbstractNous avons étudié les propriétés magnétiques d'eutectiques Pb/Sn á lamelles orientées, le champ magnétique H étant toujours dans le plan des lamelles. Nous avons surtout mesuré la perméabilité superficielle en radiofréquence: les seuls grains intervenant dans ces conditions sont ceux qui sont à la surface de l'échantillon pour lesquels le flux pénétre beaucoup plus réversiblement que dans les régions intérieures. L'épaisseur des lames (Sn) est dans la plupart des cas assez notablement supérieure à la longueur de cohérence. Dans ces conditions, dès que le champ statique H est plus grand que le champ critique de l'étain, le flux pénètre dans chaque lame d'étain. La surface traversée par le flux dans une lame peut être mise sous la forme δ × 2 (d ‐ ϱ) où δ représente le diamètre des grains, 2 d l'épaisseur de la lame d'étain et ϱ un terme correctif dû aux effets de proximité. Les valeurs et les variations, avec T et H, de ϱ sont en accord qualitatif avec les prévisions théoriques. Les comparaisons quantitatives sont compliquées par certains effets de migration atomique aux interfaces, qui se traduisent en particulier par des phénomènes de vieillissement.