bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Compressive Deformation Behavior of Long Range Ordered Polycrystalline iron—aluminum Alloys
Authors: Leamy H. J. , Kayser F. X. 
Published: July 2007

AbstractThe compressive deformation behavior of polycrystalline iron‐aluminum alloys has been investigated (i) at 298°K for specimens heat treated in various ways and containing from 22.0 to 31.7 at% Al, and (ii) from 77 to 655°K for well‐annealed specimens containing 26.6 at% Al. Alloys which possess significant DO3 type long range order exhibit marked composition and temperature dependent variations in deformation behavior. Specifically, those containing ⪆ 27 at% Al exhibit two linear and one parabolic deformation stage at 298°K. The linear stages are shown to be a result of the production and motion of DO3 type superlattice dislocations. The absence of these stages in well‐annealed specimens is attributed to the lack of thermal assistance for the DO3 superlattice dislocation nucleation process. The flow stress levels which characterize the two linear stage behavior agree with calculations of the stress required for production of antiphase boundaries. Results obtained from quenched specimens are in agreement with the above conclusions, and the changes induced by quenching are in accord with calculations of the effect of thermal antiphase boundaries upon dislocation motion.
Infrared Absorption in Gallium Phosphide
Authors: Pikhtin A. N. , Yaskov D. A. 
Published: July 2007

AbstractAn investigation was made on the infrared absorption spectra of gallium phosphide single crystals doped with different impurities in the temperature range from 90 to 420°K. With decreasing temperature a transformation of the absorption spectrum due to interband transitions between conduction band valleys to the absorption spectrum due to impurity states was observed. On the basis of a theoretical analysis of the results obtained, a number of parameters of the GaP band structure and impurity states characteristics have been determined.
Effect of Impurities on the Individual Dislocation Mobility in Silicon
Authors: Erofeev V. N. , Nikitenko V. I. , Osvenskii V. B. 
Published: July 2007

AbstractAn investigation was made of the dependence of individual 60° and screw dislocation velocities on stress, temperature, and impurity (B, As, Sb) concentration in silicon single crystals. It was found that both donor and acceptor impurities result in decrease of the activation energy (U) of the dislocation motion. The donor influence on U is stronger. The possible reasons for the observed phenomenon are analysed in terms of the effect of impurities on the mechanism of overcoming of Peierls stresses by a dislocation.
Elastic Strains during Decomposition of Homogeneous Solid Solutions — Periodic Distribution of Decomposition Products
Authors: Khachaturyan A. G. 
Published: July 2007

AbstractA decomposition is considered of an elastically anisotropic homogeneous solid solution in two phases having the same structure as that of the original solution. The following assumptions are made: 1. The phases differ in their composition and the specific volume only. 2. The inclusions of precipitating phases are coherent and have the same elastic moduli as those of the matrix. The configuration and inclusion shape is assumed to be determined by minimizing the elastic energy associated with the difference in specific volumes of the phases. A theoretical analysis for the alloys with negative elastic anisotropy leads to the configuration with a minimum of the elastic energy when the inclusions are distributed periodically. In this case the mechanism of the formation of periodic distributions differs considerably from that proposed by Cahn. Three types of metastable periodic distributions are possible, enumerated below in order of increasing elastic energy. Firstly, there is an one‐dimensional distribution representing the system of similar parallel laminated inclusions, regularly spaced along a cubic plane (e.g. (001)). Secondly, there is a two‐dimensional distribution which may be viewed as a planar square macro‐lattice formed by inclusions. The two basic translation vectors lie along the 〈100〉 orthogonal cubic directions. Finally, there is a three‐dimensional distribution, representing a primitive cubic macro‐lattice, the site of which are inclusions of equilibrium phases and of the partially decomposed matrix.
Franz‐Keldysh Effect on Indirect Transitions in GaP
Authors: Gasakov O. , Nasledov D. N. , Slobodchikov S. V. 
Published: July 2007

AbstractThe change of the spectral photosensitivity of GaP p‐n junctions with electric field has been investigated. The Franz‐Keldysh effect on indirect Γ15v → X1, Γ15v → X3 transitions has been found. The Γ15v → X1 transitions involve emission and the absorption of TA (Eph = 0.013 eV) and LA (Eph = 0.035 eV) phonons, the Γ15v → X3 emission and the absorption of TO phonons (Eph = 0.047 eV). The value of EΓ15v → X3 amounts to 2.630 eV and that of EΔ to 0.37 eV.
Some Factors Influencing the Visibility of Dislocations in Transmission Electron Microscopy
Authors: Loretto M. H. , France L. K. 
Published: July 2007

AbstractAn investigation has been made into the degree of deviation (sg) from the Bragg conditions required to make dislocations (of Burgers vector b) effectively invisible for a variety of diffracting vectors (g) when the condition g ± b = ± 1 obtains. It is found that these values of sg decrease as the magnitude of g increases, thus making confusion of the g · b = = ± 1 and g · b = 0 cases more likely for large values of g.
The Phase Transition in CsCl Mixed with CsBr, RbCl, and KCl
Authors: Weijma H. , Arends J. 
Published: July 2007

AbstractThe phase trans tion in single crystals of CsCl mixed with CsBr, RbCl, and KCl was investigated by means of ionic conductivity measurements and differential thermal analysis. Adding RbCl or KCl to CsCl reduces both the transition temperature, Ttr, and the enthalpy of transformation, ΔHtr. In the system CsClCsBr Ttr shifts to higher values relative to that of pure CsCl, whereas ΔHtr decreases considerably. A thermodynamical consideration of the phase transition temperatures in the CsClCsBr system shows that pure CsBr should exhibit a transition from the B2 to the B1 structure at 880 °C with an enthalpy variation of (300 ± 100) cal/mol. From the DTA experiments one should expect an enthalpy of (100 ± 50) cal/mol for the transformation of pure CsBr.
Quenching Experiments with High‐Purity Iron
Authors: Glaeser W. , Wever H. 
Published: July 2007

AbstractIron wire of very high purity was quenched in a helium cryostat. Changes in electrical resistivity were used to measure the recovery during isochronal and isothermal annealing in the temperature range 4.2 to 1000 °K. Two sharp recovery stages were observed (first stage: 300 °K < T < 400 °K, second stage: 400 °K < T < 520 °K). The activation energy was determined by the change in slope and the Meechan‐Brinkman test (first stage: 0.48 to 0.51 eV, second stage: 1.05 to 1.1 eV). Both recovery processes follow a first‐order kinetic law. These two stages are observed after cold work as well. The first stage is attributed to the migration of carbon atoms alone and paired with vacancies, the second stage corresponds to the migration of vacancies. The recovery spectrum exhibits in three different temperature ranges a resistivity increase and a final recovery stage in the range 850 to 1000 °K. The last increase and recovery stage may be due either to the redissolution of carbon atoms or to Bloch wall motion.
Effect of High Pressure on the Energy Gap of Indium and Thallium Superconducting Films
Authors: Galkin A. A. , Svistunov V. M. , Dikii A. P. 
Published: July 2007

AbstractThe effect of high pressure (up to 15000 atm) on the energy gap of In and Tl superconducting films was investigated by the tunnel effect on superconductor–barrier–superconductor systems. As directly found in the experiments, the In values 2 Δ/kTc indicate a reduction of the electron–phonon interaction under pressure for this metal. In the range up to 8 katm the value 2 Δ/kTc for Tl remained constant within the experimental error and was found to be 3.64 ± 0.06.
On Non‐Equilibrium Effects in Solid State Rate Processes
Authors: Geszti T. 
Published: July 2007

AbstractAt temperatures high enough to make thermally activated hopping sufficiently fast and at correspondingly high frequencies, inelastic or dielectric relaxation (damping) due to point defects may show the following deviations from the predictions of equilibrium theory: a) the main damping maximum appears at a frequency lower than predicted by equilibrium theory, b) the intensity of the main maximum is reduced, c) secondary damping maxima appear at eigenfrequencies of the energy exchange between defect and surroundings. The analysis shows that experimental detection of these effects is most easily realizable on defect systems with slow energy exchange with the surrounding crystal, and low activation energy.
Vineyard's Theory of the Kinetics of Ordering and Lidiard's Consistency Conditions
Authors: Sohoijet M. 
Published: July 2007

AbstractLidiard's consistency conditions are extended to the case of alloys of face centered cubic structure. By separating the jump rates into a part originating in the saddle point atoms and a part originating in the other neighbors it is shown that a Vineyard type of theory does not verify Lidiard's consistency conditions except in the limiting cases of complete order and complete disorder.
On the Experimental Observation of Small Polarons in Rutile (TiO2)
Authors: Bogomolov V. N. , Firsov Yu. A. , Kudinov E. K. , Mirlin D. N. 
Published: July 2007

AbstractA careful analysis of certain observations concerning the polaron nature of current carriers in rutile is presented. The criticism of our paper [1] given in [2] is shown to be unfounded.
The Electrical Resistance of Palladium and Palladium–Gold Alloy (50 wt% Au and Pd) in Gaseous Hydrogen up to 24000 at at 25 °C
Authors: Baranowski B. , Wiśniewski R. 
Published: July 2007

AbstractThe outline of a high‐pressure advice for gaseous hydrogen as a double piston‐cylinder system is given. Any contact between the gaseous volume and the pressure‐transmitting liquid is avoided. The electrical resistance of Pd and Pd–Au (50 wt%) foils was measured at (25 ± 0.1) °C up to 24000 at of gaseous hydrogen. A linear relationship of relative electrical resistance versus the logarithm of the hydrogen fugacity is observed. The relative electrical resistance of Pd as function of the atomic ratio H:Pd is estimated.
On the Influence of Surface Roughness on the Magnetization Ripple in Ferromagnetic Thin Films
Authors: Maksymowicz A. , Maksymowicz L. , Lubecka M. 
Published: July 2007

AbstractA model is proposed in which the decisive influence on magnetization ripple is exerted by demagnetizing fields produced by surface charges due to the roughness of the surface of the thin film. The model predicts periodical fluctuations of the magnetization vector around the mean magnetization direction. The expressions obtained for the ripple amplitude and periodicity are where
equation image
a is the effective value of the surface roughness and t the thickness of the film. The theoretical results are in agreement with the experimental data of other authors.
Compensation of Trivalent Europium and Ytterbium Ions in Calcium Fluoride by Interstitial Hydride Ions
Authors: Chambers D. N. , Newman R. C. 
Published: July 2007

AbstractHydrogen has been diffused into calcium fluoride crystals doped with Eu, Yb and other Rare Earths. The local mode absorption from H− ions has been measured before and after X‐ or γ‐irradiations and a detailed study has been made of the new electronic transitions of Yb3+ ions near 1 μm which appear after the irradiation. It is concluded that for Eu and Yb dopings, RE3+—H−(i) pairs are produced which are thermally unstable. In CaF2:Yb crystals, a second centre involving two hydride ions has also been identified.
Dynamical Theory of Hydrogen Diffusion in Cubic Metals
Authors: Lepski D. 
Published: July 2007

AbstractStarting from a criticism of the classical rate theory for diffusion processes and its quantum derivatives a dynamical theory for the diffusion of light interstitial impurities in crystals based on Kubo's work is derived and applied to an one‐dimensional model for hydrogen diffusion in cubic metals. It appears that hydrogen diffusion in the b.c.c. metals must be treated quantum mechanically in a band model, whereas for f.c.c. metals a classical theory seems more suitable. In the quantum (b.c.c.) case we obtain a remarkable isotope effect in the activation energy, which depends strongly on the model potential used, and a pre‐exponential factor, D0, approximately proportional to the inverse of the particle mass.
Potential Fields of Parallel Edge Dislocation Arrays
Authors: Neubert D. 
Published: July 2007

AbstractThe equipotential lines for a free test dislocation in the stress field of fixed parallel edge dislocation arrays are calculated from linear elasticity theory. The potential fields determine the path a free dislocation will take under ideal conditions. The well known fact is demonstrated that from an energetic point of view edge dislocations prefer to arrange in a wall rather than in a glide plane, namely by the positions of the calculated potential valleys which give the stable positions for the free test dislocation. Calculations are presented for characteristic arrays with a small number of dislocations. As the qualitative features of the results will hold also for arrays with a large number of dislocations some conclusions are drawn on the process of polygonization and a comparison with properties of edge dislocation arrays in silicon is made.
On the Theory of Excitons in High Magnetic Fields
Authors: Fritsche L. , Heidt F. D. 
Published: July 2007

AbstractIt has been shown in a previous paper the excitonic optical absorption spectra in GaSe at high magnetic fields can be explained on the basis of a theory developed by Elliott and Loudon. In the present paper this theory is generalized by including the effects of dielectric anisotropy and non‐spherical bands. As can be expected in view of the layer‐structure of GaSe the treatment yields a considerable improvement in fitting the experimental data, especially those of the so‐called satellite lines of the exciton absorption spectrum above 30 kG.
On the Energy Transmission of Paramagnetic Ions into the Lattice through Rapidly Relaxing Centres
Authors: Skrebnev V. A. 
Published: July 2007

AbstractA investigation is made of the spin‐lattice relaxation in crystals having two kinds of paramagnetic centre whose resonance frequencies ae nearly the same and whose spin‐phonon interaction differs essentially. The concentration of centres with slower relaxation rate is considered to be greater than the concentration of rapidly relaxing centres. It is assumed that the spin‐phonon coupling of the rapidly relaxing centres is much less than the spin‐spin interactions of these centres with the other paramagnetic centres. The dependence of the spin‐lattice relaxation time of centres which ae weakly bounded to the lattice and which relax through rapidly relaxing centres on the splitting difference of their spin levels, on the value of spin‐spin interactions between them, on their concentration, and on the value of the spin‐phonon interaction of the rapidly relaxing centres is established.
The Nature of DC Field Effect Relaxation in Photoconducting CdS
Authors: Weber E.‐H. 
Published: July 2007

AbstractIt is shown that the real surface of photoconducting CdS crystals is usually contaminated by CdSO4. From de field effect and photocurrent measurements it can be concluded that CdSO4 has a donor‐like action at the surface which leads to a reduced recombination rate for photocarriers near or at the surface. Apparently no slow surface states are present on a contaminated surface; the slow relaxation of field effect seems to be determined mainly by volume trapping centres within the space‐charge region.
Magnetic Properties of FeCr2S4 and CoCr2S4
Authors: Gibart P. , Dormann J.‐L. , Pellerin Y. 
Published: July 2007

AbstractNew measurements of magnetic properties of pure FeCr2S4 and CoCr2S4 have been carried out. The g‐factors of cobalt, iron, and chromium in these compounds were evaluated. Exchange interactions were deduced from computation of the experimental paramagnetic and magnetization curves.
Deformation of Molecular Crystals at Electronic Excitation
Authors: Davydov A. S. 
Published: July 2007

AbstractIn this article an investigation is made of deformation of the molecular crystal due to electronic excitation. It is shown that in a three‐dimensional crystals at a sufficiently large resonance interaction between molecules the states of free excitations with positive effective mass correspond to minimum of the total energy of the crystal. The transition to local excitations requires activation energy. The states of the free excitons with negative effective masses in three‐dimensional and one‐dimensional crystals are unstable. Exciton states with positive effective masses in one‐dimensional crystals are represented as modulated plane waves. Distribution of the excitation along some length of the crystal corresponds to these waves. The stronger is the resonance interaction between molecules, the more is this length.
Die Deutung sekundärer Eigenschaften des Bordoni‐Maximums in einem Mehrmuldenmodell der Doppelkinkrelaxation
Authors: Engelke H. 
Published: July 2007

AbstractEin in einer vorangegangenen Arbeit abgeleitetes Modell für die Bewegung von Versetzungsbögen im Peierls‐Potential wird in vereinfachter Form dazu benutzt, mechanische Dämpfungsmaxima im amplitudenunabhängigen Bereich zu berechnen. Ein Vergleich mit gemessenen Bordoni‐Maxima ergibt gute Übereinstimmung für die Relaxationsstärke und den präexponentiellen Faktor der Relaxationszeit. Bei Annahme plausibler Verteilungen der Bogenlängen und der inneren Spannungen erhält man näherungsweise eine von D. O. Thompson gefundene Λ2‐Abhängigkeit der Relaxationsstärke (Λ mittlere Bodenlänge) und Temperaturverschiebungen der Maxima in der richtigen Größenordnung. Obwohl die berechneten Maxima gegenüber einfachen Relaxationsmaxima erheblich verbreitert sind, scheint eine Deutung der vollen Breite des Bordoni‐Maximums eine strengere Behandlung des Modells zu erfordern.
Polishing Damage and Luminescence in p‐Type GaAs
Authors: Tuck B. 
Published: July 2007

AbstractThe photoluminescence of zinc‐doped GaAs has been studied for different surface preparations. Mechanically polished specimens fluoresced less than chemically prepared ones. Etch‐pit studies using a dislocation etch indicated that mechanical polishing introduced dislocations and samples showing the largest number of etch pits showed the weakest photoluminescence. It was also shown that diffusing a large concentration of zinc into n‐type GaAs introduces dislocations, and it is suggested that this is the reason for the low photoluminescence efficiency of zinc‐doped GaAs for concentrations in excess of 1019 cm−3.
Radiative Recombination in Silicon p‐n Junctions
Authors: Michaelis W. , Pilkuhn M. H. 
Published: July 2007

AbstractThe electroluminescence of silicon was investigated in the temperature range between 300 and 77 °K. The near edge emission is due to indirect band‐to‐band transitions associated with TO and TA phonon emission/absorption. The intensity‐voltage relation shows that this emission is connected with the diffusion current. At low voltages, additional long wavelength emission is observed which is connected with recombination in the space charge region. An absolute measurement of the internal quantum efficiency yields a room temperature value of 2 × 10−6 for the band‐to‐band emission. This value is well described by a theoretical radiative lifetime derived from van Roosbroeck‐Shockley statistics and by an experimental non‐radiative lifetime.
Far Infrared Reflectivity of SbSI
Authors: Petzelt J. 
Published: July 2007

AbstractFar infrared reflectivity of SbSI bulk crystals in a polarized light was measured in the temperature region between −185 and 80 °C and frequency from 400 up to 15 cm−1. The optical constants and dielectric constant were calculated using Kramers‐Kronig analysis. The experimental data were compared with the results of the group‐theoretical analysis of normal vibrations. Soft mode behaviour was observed in the lowest frequency region (below 100 cm−1) and parameters of the corresponding oscillator were calculated. The mode frequency shifts from 32 cm−1 at 60 °C to 22 cm−1 at 25 °C. The oscillator strength is not high enough to explain the whole value of the static dielectric constant so that still another lower frequency resonance as observed by Grigas and Karpus in the centimetre region or a relaxation as observed by Vu Huy Dat in megacycle region should exist.
Effect of Three‐Body Forces on the Shell Model of Alkali Halides: Application to KBr and KI
Authors: Singh R. K. , Verma M. P. 
Published: July 2007

AbstractThe three‐body coupling coefficients computed in an earlier paper [14] have been injected in the shell model of ionic solids treating both the ions as polarizable. This modified shell model has been used to compute the dispersion curves and the two phonon combined density of states (C.D.S.) curves of KBr and KI. Excellent agreements have been obtained with the results of neutron scattering and Raman scattering experiments.
Die Behandlung von Fehlern im Fußliniengitter der Supraleiter 2. Art in der Nähe von Hc2
Authors: Brandt E. H. 
Published: July 2007

AbstractAbrikosovs Methode zur Berechnung der Energie und Struktur eines regelmäßigen Flußliniengitters in Supraleitern 2. Art in der Nähe von Hc2 mit Hilfe der linearisierten Ginsburg Landau‐Gleichungen wird auf die Behandlung von Störungen im Flußliniengitter erweitert. Die Fehlerenergie kann als Integral über den ganzen Supraleiter geschrieben werden. Durch Variation dieses Ausdrucks erhält man das Verschiebungsfeld des Fehlers. Der Schubmodul des Flußliniengitters wird berechnet. Sowohl die Fehlerenergie als auch der Schubmodul gehen für Ha → Hc2 wie (Hc2Ha)2 gegen Null.
Low‐Temperature Internal Friction in Deformed Single Crystals of Niobium and Niobium‐Molybdenum Alloys
Authors: Amateau M. F. , Mitchell T. E. , Gibala R. 
Published: July 2007

AbstractThe low‐temperature internal friction spectrum has been measured on single crystals of Nb and Nb‐Mo alloys deformed in tension. The α‐peak height is found to increase in proportion to the square of the work‐hardening stress and, therefore, in direct proportion to the dislocation density. The addition of interstitial impurities or substitutional molybdenum is found to increase the frequency factor of the α‐peak without changing the activation energy. The maximum peak height is decreased substantially both by impurities and by decreasing the deformation temperature. It is concluded that the α‐peak is similar to the Bordoni peak in f.c.c. metals and is due to either an intrinsic dislocation mechanism (most likely kink nucleation on non‐screw dislocations), which is sensitive to impurities, or an extrinsic mechanism in which impurities are more directly involved. Some preliminary observations on the β‐peak are also presented.