bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Mobility of Grown‐in Dislocations in the Intermetallic Compound MgZn2 II. Stress Dependence of Basal Slip at 390 °C
Authors: Paufler P. , Marschner J. , Schulze G. E. R. 
Published: July 2007

AbstractThe velocity ẋ of grown‐in (0001) 〈1210〉 dislocations in the intermetallic compound MgZn2 has been determined as a function of the shear stress τ at 390 °C. The results show that ẋ fits an exp (—const/τ) dependence as in the case of prism slip. Comparison of basal and prism slip gives evidence for a low anisotropy of the Peierls stress. Microscopic measurements are in good agreement with stationary creep data when experimental results of the mobile dislocation density are used.
Heat Transport in Impure Insulators at Low Temperatures
Authors: Joshi Y. P. , Verma G. S. 
Published: July 2007

AbstractThe Boltzmann transport equation is solved for phonons in an impure insulator slab to obtain the simplest possible and physically plausible solution. The equation is not treated as a boundary value problem, but it is assumed that the occupation number for phonon states corresponding to a given frequency and polarization is a smooth function of the direction of phonon wave vector. Heat flux and energy density in the crystal are studied when such a solution is assumed to exist.
Extrinsic Stacking Faults in Iridium
Authors: Fortes M. A. 
Published: July 2007

AbstractThe stacking faults in Shockley type loops, observed in iridium field‐ion images, have been analyzed for the type of fault, using a method developed in a previous paper [1]. In all cases where the identification was possible, the faults were found to be extrinsic. This result is discussed in the light of the origin of the defects, and related to the large negative hydrostatic pressures that occur in field‐ion specimens.
Helmholtz Free Energy of an Anharmonic Crystal: A Green Function Approach
Authors: Shukla R. C. , Muller E. B. 
Published: July 2007

AbstractThe thermodynamic Green function of a weak anharmonic crystal, obtained through the equation of motion method, has been used to derive an explicit expression for the interaction energy. The Helmholtz free energy (F) has been obtained by integrating this interaction energy over a formal coupling parameter. Under certain conditions the expression for F has been shown to be identical with that obtained from perturbation theory and diagrammatic methods.
Polarization Effect in the Soft X‐Ray Absorption of CdS
Authors: Watanabe M. , Yamashita H. , Nakai Y. , Sato S. , Onari S. 
Published: July 2007

AbstractA strong polarization dependence of the optical transition from the inner core level is observed in the S LII,III absorption spectra of hexagonal CdS (160 to 170 eV), using the synchrotron orbital radiation. The present results are discussed in comparison with the interpretation made on reflection spectra obtained in the ultraviolet region (3 to 12 eV).
Electron Energy Losses and Optical Constants of Ne and CH4
Authors: Daniels J. , Krüger P. 
Published: July 2007

AbstractFrom energy loss measurements of fast electrons on solid neon and methane the energy loss functions Im (−1/ε) and the dielectric constants ε = ε1 + iε2 are calculated. The ε2‐spectra of the solids are compared with the energy loss spectra of gaseous Ne and CH4.
Optical Properties of Cadmium Single Crystals
Authors: Schwarz H. 
Published: July 2007

AbstractThe optical properties of cadmium single crystals and of a cadmium film deposited by vacuum evaporation were measured in the energy range from 0.5 to 5.5 eV in dependence on temperature, crystal orientation, and the pressure in the vacuum chamber. The results prove that oxide layers become effective only at higher energies. The influence of adsorbed impurity films, which arise on the sample surfaces at low temperatures, is negligible at a pressure of p = 10−9 Torr, while the results obtained at higher pressures are falsified in the whole energy region investigated. The results obtained at a pressure of p = 10−9 Torr agree with theoretical calculations of the optical absorption.
Covalent bonding effect on Van Vleck paramagnetism in AIIBIII2CVI4 semiconductor compounds
Authors: Manca P. , Muntoni C. , Raga F. , Spiga A. 
Published: July 2007

AbstractThe magnetic susceptibility of some AIIBIII2CVI4 defect tetrahedral compounds was measured at room temperature. The experimental data are analyzed along the line of previous theoretical considerations in which the Langevin and the Van Vleck magnetic susceptibility components are described, respectively, in terms of atomic and bonding parameters of the compounds considered. A comparison of the experimental results with those of ANB8–N normal tetrahedral compounds can be made by introducing the number of bonds per formula as a normalization factor.
Theory of the current‐voltage (I‐U) characteristics of monopolar and quasi‐monopolar semiconductors with different intensities of contact and volume injection
Authors: Zyuganov A. N. , Pismennyi Yu. G. , Svechnikov S. V. 
Published: July 2007

AbstractAn undiffused theory of the static current‐voltage characteristics of photosensitive semiconductors is proposed within the limits of the two‐level band scheme which is usual for such materials. The analysis of I‐U characteristics permits the determination of some parameters of the band scheme, injecting properties of the contact and to fix the switching of recombination channel under the conditions of excitation of the semiconductor in the intrinsic absorption region. The finite value of contact injection leads to definite values of the greatest slope of the I‐U characteristic in the region of trap filled limited voltage (VTFL).
Étude spectroscopique du grenat d'europium gallium (EuGaG)
Authors: Boccara A. C. , Briffaut J. P. , Hodges J. A. , Moreau N. 
Published: July 2007

AbstractA partir du spectre d'absorption du grenat d'europium gallium (EuGaG), nous avons déterminé les paramètres A02 et A22 de l'hamiltonien du champ cristallin agissant sur Eu3+. Le modèle de charges pontuelles se révèle, dans ce cas, très satisfaisant pour le calcul du rapport A22/A02. Des mesures de dichroïsme circulaire magnétique (DCM) nous ont permis de détecter des doublets non résolus en absorption, de confirmer le résultat obtenu par le modèle de charges ponctuelles et de déduire les facteurs de Landé des niveaux 7F1 et 5D1.
Die Dichte der beweglichen Versetzungen in Germanium
Authors: Springer E. 
Published: July 2007

AbstractMittels Doppelätzungen wird in Germanium‐Einkristallen der Anteil der bewegten unter den angeätzten Versetzungen bei Intervallverformungen bestimmt. Im Bereich I der Verformungskurve sind es ≈ 90%. Für den Bereich II ergeben sich Anhaltspunkte, daß der Prozentsatz der bewegten unter den angeätzten Versetzungen wesentlich kleiner ist (nahe 45%).
Surface electron‐phonon interaction
Authors: Ilkovič V. 
Published: July 2007

AbstractThe scattering of conduction electrons by surface waves is studied theoretically basing on energy considerations. The relaxation time for this scattering mechanism and the quantity \documentclass{article}\pagestyle{empty}\begin{document}$ (\overline {\partial \varepsilon /\partial t})_s $\end{document} characterizing the mean energy which is transferred by the conduction electrons to the surface lattice per unit time are calculated.
The optical anisotropy of cubic nickel‐iodine boracite due to quadrupole transitions
Authors: Pastrňák J. , Cross L. E. 
Published: July 2007

AbstractMeasurements of the optical absorption of NiI boracite crystals for [100], [110], and [111] directions of light propagation reveal an unexpected angular dependence of the value of absorption coefficient and for the [110] direction also a dependence on the orientation of the plane of polarization of the incident light. These results as well as the existence of pronounced birefringence for the [110] direction of light propagation can be explained by the presence of quadrupole transitions. The results obtained are compared with Hellwege's theory of quadrupole transitions [1]. The functions which describe the angular dependence of the radiation probability for a cubic crystal with quadrupole transitions are found to be in agreement with the experimental results, if the theoretically determined functions [1] are taken in linear combination so as to fulfill the requirement of cubic symmetry.
Generalized exchange interaction and Kondo effect
Authors: Ganguly B. N. 
Published: July 2007

AbstractThe internal degree of freedom of the impurity atom is taken into account in calculating the anomalous part of the resistivity leading to the Kondo effect. This is achieved by adopting a generalization of the usual s—d exchange interaction, first proposed by Vonsovskii and Svirskii. We find that, if the intra‐atomic exchange interaction is neglected, the logarithmically divergent character of the anomalous part of the resistivity is retained with an effective coupling strength. It is argued that the inclusion of the intra‐atomic exchange term may affect the logarithmically divergent character of the conduction electron scattering amplitude near the Fermi surface.
On the acoustical asymptotics of the phonon spectrum of a finite crystal
Authors: Iosilevskii Ya. A. 
Published: July 2007

AbstractThe acoustical asymptotics of the spectral distribution of the vibrations of separate atoms in dependence on their positions in the crystal are considered for the cases of a semispace and a plane‐parallel plate of arbitrary thickness. The general solution of the problem is obtained in the case of an arbitrary orientation of the boundary surfaces with respect to the crystallographic axes. In the elastically isotropie continuum approximation this solution is analysed in detail. For the surface atoms the tensor of the Debye effective frequencies is constructed. The method is taken from the dynamics of a crystal with extended defects which in the case under consideration are the stress‐free plane boundaries and is based on an accurately solving of integral equations such as the Dyson ones. The results obtained are discussed in connection with the mean square fluctuations of the positions and momenta of the crystal atoms determining the intensity and the energy position of the Mössbauer no‐phonon line and the Debye‐Waller factor in the cross section of the low‐energy particles. They are also discussed with respect to the surface contribution to the low‐temperature heat capacity. In particular, the statistical weight of the Rayleigh waves in the scale of the squared frequencies is shown to be proportional to √ω2 as well as the density of the three‐dimensional phonon states. Thus the surface vibrations do not lead to deviations of order T2 from the T3‐behaviour of the lattice thermal capacity. Such deviations are due to the surface not in itself as a two‐dimensional manifold but to its closeness, leading to quantization of the volume vibrations and to appearance of new specific modes.
Thermal conductivity of indium antimonide at low temperatures
Authors: Kosarev V. V. , Tamarin P. V. , Shalyt S. S. 
Published: July 2007

AbstractA detailed experimental investigation was made of the phonon thermal conductivity on n‐ and p‐type indium antimonide of single crystals (carrier concentrations 1014 to 1018cm−3) in the temperature range 2 to 100 °K. It is shown that the experimental results may be explained by a new mechanism of phonon scattering by charge carriers in the electrical field of impurity centres [2] and a more consistent consideration of the role of normal processes of phonon‐phonon interaction at low temperatures.
Electromultipole interaction and paramagnetic relaxation in ruby. IV. Spin‐lattice relaxation
Authors: Peskovatskii S. A. 
Published: July 2007

AbstractThe influence of the stretched line wings on the spin‐lattice (longitudinal) relaxation rate is considered. It is shown that in the spin‐system with long line wings even the direct process of the spin‐lattice energy exchange may involve mainly nonresonant phonons. The component of the relaxation rate owing to the wing (Wg) has a stronger temperature dependence than that of the conventional direct process. The shape of the line wings determines the power of this dependence, The wings of the quadrupole‐quadrupole broadened lines give n = 2.4. The relaxation owing to the wings explains anomalies in the temperature, concentration, and frequency dependences of the longitudinal relaxation rate observed. The relaxation model proposed fits well the experimental results of Cr3+ ions in corundum and rutile. It is quite possible that this model plays an important role in other paramagnetics, too.
Optical properties of silver iodide
Authors: Suri S. K. , Henisch H. K. 
Published: July 2007

AbstractMeasurements are reported of the fundamental optical absorption edge, its temperature dependence and anisotropy, for pure and copper‐doped β‐AgI single crystals grown by the gel method. The temperature range spans the β → α phase transition. Studies of photoluminescence and cathodoluminescence are also described, and interpreted in terms of band and defect structure.
Free excitons and optical spectra of semiconductors
Authors: Auvergne D. , Camassel J. 
Published: July 2007

AbstractIt is shown, that the excitonic wave functions exhibit a discontinuity at the transition between free and bound states. In the real case where carriers spend a finite time on excited levels, it is possible to neglect the Coulomb interaction when the two particles have a kinetic energy greater than a few Rydbergs. Using this hypothesis, an absorption curve in good agreement with the experimental results on GaAs is calculated.
Low lying resonant band modes in CsBr and CsI crystals doped with In+ and Tl+
Authors: Prettl W. , Siep E. 
Published: July 2007

AbstractMeasurements of the far infrared absorption due to In+ and Tl+ impurities in CsBr and CsI single crystals yielded low frequency resonances with narrow linewidths at 11.0 cm−1 in CsBr:In+, 12.0 cm−1 in CsI:In+, 14.1 cm−1 in CsI:Tl+, and 16.95 cm−1 in CsBr:Tl+. The frequencies of the resonant band modes in the Tl+ doped crystals shift to higher values with increasing temperature. Using a model of the perturbed crystal which involves the mass defect and the change of the central force constants between the defect and its eight nearest neighbours, the force constant change is fitted to the various resonance frequencies. The resulting linewidths are compared with the experimentally determined values.
The mössbauer study of Fe57 and Sn119 in FeSn at 5 °K
Authors: Ligenza S. 
Published: July 2007

AbstractMössbauer investigations have been performed for both Fe57 and Sn119 nuclei in FeSn at 5 °K. The numerical analysis of the absorption spectra and calculations of the hyperfine parameters have been made using the GIER computer. It was found that 1/6 of the total number of Fe spins is aligned at an angle of 60° relative to the main spin directions [100] or [210]. The values of the effective field for iron atoms is discussed in terms of the difference in isomer shifts.
Analysis of point defect states in copper. III. Interaction between copper interstitials and impurities
Authors: Kraut A. , Dworschak F. , Wollenberger H. 
Published: July 2007

AbstractThe influence of impurities on the production of stable defects by electron irradiation at 80 °K has been studied in dilute alloys of copper with Ni, Mn, Au, Mg, or Sb. Using damage rate measurements the capture radii of the different impurities for freely migrating copper interstitials are determined with respect to the capture radius of the vacancy (rt/rv). The interstitial impurity interaction can quantitatively be accounted for by the continuum theory of elasticity.
The critical magnetic field of thin superconducting films
Authors: Litovchenko V. A. 
Published: July 2007

AbstractIn recent papers [1 to 4] on critical magnetic field of superconducting films the one‐electron state is treated almost in a “semiclassical” way. Though the motion of electrons in the direction of the film thickness is described by a quantum number n [2], the special features of electron pairing in thin films were not taken into account. Thus the results are valid only for thick metal films (L ≧ 10−5 cm). In this paper the quantization of electron motion in the direction of the film thickness is taken into account. This motion is described by a wave function Ψ(z) and a quantum number n. Moreover Cooper pairs are built in a correct way [5]. He is calculated for thin metal films. In the limiting case of thick films the result agrees with that of [2]. Furthermore, the approach used permits to study semi‐metal and semiconducting films too, where Hc is calculated for the whole range of thicknesses (50 to 1000 Å). All results are valid near Tc.
Effect of uniaxial compression on the thermomagnetic effects in bismuth
Authors: Ertl M. E. , Rahman I. U. 
Published: July 2007

AbstractThermomagnetic transport parameters have been measured in bismuth at 80 °K and found to be strongly pressure‐dependent. Results indicate that in addition to a decrease in the energy overlap, E0, there is an increased participation of a light hole band increasing the mobility of holes. The Nernst effect and the magneto‐Seebeck effect are particularly sensitive to changes in hole mobility. In some orientations the Seebeck voltage in a field of 0.47 Wb/m2 can change sign under uniaxial compression.
Hyperfine fields in concentrated FeCr alloys
Authors: Schwartz L. H. , Chandra D. 
Published: July 2007

AbstractMössbauer spectra of alloys in the range Fe–24 at% Cr to Fe–60 at% Cr have been analyzed using an extension to high concentrations of the results for dilute alloys. The decrease in hyperfine field at an Fe nucleus due to the presence of one Cr near or next near neighbor was found to be 7.5%, concentration independent over the range studied, and in excellent accord with the value of 7.6% found for dilute alloys of Cr in Fe. The isomer shift per Cr neighbor was found to be −0.02 mm/s, also independent of concentration and in good agreement with the value of −0.03 mm/s found for dilute alloys. The same parameters gave equally satisfactory fits to the spectra for randomly polarized absorbers and for high field experiments with the absorber magnetization saturated parallel to the direction of γ‐ray propagation.
Influence of the Electric Field on the Exciton Absorption in Germanium
Authors: Aronov A. G. , Mochan I. V. , Zemskii V. I. 
Published: July 2007

AbstractIn germanium the electro‐absorption in the indirect absorption region was measured by two differential methods: the method of frequency modulation and the method of electro‐modulation. The experimental results are compared to calculations taking the electron–hole interaction into account. A quantitative description of the electro‐absorption spectra is obtained both for the allowed and for the forbidden transitions. It is shown that the first maximum of the electro‐absorption spectrum corresponds to the threshold energy in the case of allowed transitions (if no broadening effects are taken into account), whereas for the forbidden transitions the zero‐point corresponds to the threshold energy. The Franz‐Keldysh effect was also observed in the region of transitions to the continuous spectrum. This effect is found to be considerably smaller than the effects leading to the change of the absorption coefficient by the electric field in the region of transitions to the exciton band.
Interpretation of Far UV Spectra in Solid Rare Gases from Calculated Density of States
Authors: Rössler U. 
Published: July 2007

AbstractThe conduction band density of states has been calculated for solid Ar, Kr, and Xe on the basis of KKR energy bands. The joint density of states between conduction bands and core states is determined and an interpretation of core excitation spectra of solid Ar, Kr, and Xe is given. The results show that up to minor excitonic effects the far uv spectra are mainly determined by the conduction band density of states.
The Mössbauer Line Shape for Divalent Iron in Silver Chloride Crystals
Authors: Tumolillo T. A. 
Published: July 2007

AbstractThe Mössbauer line shape is calculated for 57Fe in a fluctuating electric field gradient. This gradient is produced by the random jumping of a charge compensating positive ion vacancy which is bound to divalent iron in silver chloride. In order to simplify the calculations the vacancy is only allowed to occupy the nearest and next nearest positive ion sites with respect to the iron ion. Examples of computed spectra are presented and discussed.
Calculation of the Mössbauer Parameters for a Disordered Cubic Crystal Lattice
Authors: Srivastava B. P. , Sharma H. N. K. , Bhattacharya D. L. 
Published: July 2007

AbstractA theoretical expression is derived for a cubic crystal lattice disordered by the introduction of a vacancy‐interstitial pair. Considering only the nearest neighbour interaction for the interstitial atom, the double‐time Green's function has been formally calculated and the ratio of the Debye‐Waller factor for the disordered lattice to that of the perfect lattice has been obtained. It is found that in the presence of a point defect pair, the exponent ratio of the disordered lattice to that of the perfect lattice becomes [1 + 4 Γlk, × {u(−2)−(h/2 kT) u(−1)}] where γtk is a factor, for which the major contribution comes from the position vector of the interstitial atom and u(2p) is the 2 p‐th moment of the frequency spectrum of a cubic lattice.
Localized Non‐Magnetic Impurities in Metals
Authors: Dubey S. K. 
Published: July 2007

AbstractThe problem of non‐magnetic impurities in metals has been studied using the double‐time Green's function technique. An interaction term for impurity and metal interaction similar to that of Anderson has been defined. This gives rise to inelastic and incoherent scattering of the electrons. An expression has been developed for the transition probability and the temperature dependent part of the impurity resistivity.
27Al NMR Spectra in Al3d Transition Metal Alloys
Authors: Grüner G. , Kovács‐Csetényi E. , Tompa K. , Vassel C. R. 
Published: July 2007

AbstractThe electric and magnetic perturbations around Mn, Cr, and Fe impurities in aluminium were investigated by measuring the 27Al NMR spectra of these alloys. The first order quadrupole wipe‐out numbers measured at low impurity concentrations, and the magnetic field dependence of the signal amplitude in more concentrated alloys are discussed in the framework of the Friedel‐Anderson picture.
Approximate Consideration of the Wave Function Overlapping in the Heitler‐London Theory for a Crystal
Authors: Ledovskaya E. M. , Petrashen M. I. 
Published: July 2007

AbstractFor complex systems, possessing space symmetry and consisting of a large number of subsystems, “the non‐orthogonality paradox” inherent in the Heitler‐London method is practically solved. A method of summing up the permutations in the expressions for energy corrections is developed, basing on the symmetry of the space arrangement of the subsystems and on introducing a limiting distance for subsystem interactions. This method of summing is illustrated on the example of the alkali halide crystal.
Galvanomagnetic Effects of Metals due to Inelastic and Simultaneous Elastic Scattering
Authors: Clausecker K. 
Published: July 2007

AbstractThe transition probability of electrons due to scattering by phonons is derived in Born's approximation. The Wannier representation is used to characterize the displacement potential by a few matrix elements which are determined by the galvanomagnetic effects. Therefore the Boltzmann equation is solved by the new method of Fourier transformation. For additional elastic scattering of electrons by point defects, questions of Matthiessen's and Kohler's rule are discussed by interpolation formulae referring to numerical results.