bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Remarks to the Crystal Field Theory of Spinel Lattices
Authors: Jäger E. , Perthel R. 
Published: July 2007

AbstractThe crystal field potential of an octahedral site in the lattice of a normal, and an inverse spinel is calculated on the basis of the point charge model. The ten nearest neighbouring environments are taken into account. Finally, the tables of the matrix elements of the operator equivalents O and O for J = 1/2, 1, 3/2, …, 8 are given.
Electron Transmission Microscopy of NiAl
Authors: Lautenschlager E. P. , Tisone T. C. , Brittain J. O. 
Published: July 2007

AbstractAn electron transmission study of the β‐phase of NiAl was made in annealed and deformed samples with the purpose of looking for antiphase boundary (APB), networks, and super‐dislocations and to observe other configurations of the deformed state. No “grown in” APB networks, superdislocations, or APB trails were observed in annealed or deformed samples. It was concluded that in β‐NiAl APB do not exist and the material deforms on slip systems which do not require the motion of superdislocations. Deformation appears intimately related to tangles of single dislocations, subgrains, tilt and twist subboundaries, distorted hexagonal networks, and dislocation loops.
Some Optical Properties of Thin Evaporated Cd3As2 Films
Authors: Żdanowicz L. 
Published: July 2007

AbstractThe refractive index and absorption coefficient of thin evaporated Cd3As2 films are determinded from spectrophotometric transmission and reflection measurements over the range 0.5 to 12 μm. The refractive index of Cd3As2 is 4.6 at λ = 12 μm; at λ = 1.9 μ a maximum index of nmax = 5.3 is observed. In the spectral region 0.5 to 2 μm a sharp decrease is observed in the absorption coefficient, of about two orders of magnitude, from 105 cm−1 to 103 cm−1, which may be due to direct transitions. In the range 6 to 12 μm, the absorption coefficient again falls to about 102 cm−1, which probably corresponds to indirect transitions. The results obtained may explain the discrepancies in the values of energy gap quoted by different authors for Cd3As2.
Diffusion of Nickel in Silicon
Authors: Bonzel H. P. 
Published: July 2007

AbstractThe study of diffusion of nickel (Ni63) in silicon single crystals in the temperature range 450 to 800 °C supports the “dissociative diffusion mechanism” for this impurity. Rapid interstitial diffusion of Ni into Si is followed by a complex reaction of interstitials with vacancies resulting in particular concentration profiles of substitutional nickel. The production and diffusion of vacancies which has a great influence on this reaction, is discussed. The activation energy for diffusion of vacancies has been estimated to 44 kcal/mol and the self‐diffusivity in silicon can be approximately described by.
The Influence of Large Elastic Anisotropy on the Determination of Burgers Vectors of Dislocations in β‐Brass by Electron Microscopy
Authors: Head A. K. , Loretto M. H. , Humble P. 
Published: July 2007

AbstractThe theory of electron diffraction images of dislocations based on isotropic elasticity is found to be inadequate for β‐brass because of its large elastic anisotropy. In particular, the isotropic invisibility criteria (g · b = 0 and g · b × u = 0) are not valid in general in anisotropy except for pure screw or pure edge dislocations lying perpendicular to a symmetry plane of the crystal. Theoretical image profiles have been computed using the two‐beam dynamical approximation and the full anisotropic strain fields of dislocations. Comparison of the character of theoretical and experimental images has established that the majority of dislocations in β‐brass are screw dislocations having a Burgers vector of a whole 〈111〉 and gliding on {110}.
The Identification of Burgers Vectors and Unstable Directions of Dislocations in β‐Brass
Authors: Head A. K. , Loretto M. H. , Humble P. 
Published: July 2007

AbstractThe theoretical predictions of electron microscope images of dislocations in anisotropic crystals described previously are extended to identify other dislocations in β‐brass. Many dislocations having sharp bends are observed. Their Burgers vectors are 〈111〉 and their crystallography agrees well with the predicted instability of such dislocations. Dislocations of Burgers vector 〈100〉 have also been identified, lying on both {100} and {110} planes. Some dislocations with Burgers vectors 〈111〉 can be shown to be split into two ½ 〈111〉 dislocations with an ordering energy of ≈︁ 40 erg/cm2.
Thermomagnetic Effects in Anisotropic Media
Authors: Pinchuk I. I. 
Published: July 2007

AbstractComponents of the thermomagnetic tensor for arbitrary orientation of the magnetic field H and any crystallographic structure are analysed, and the case of weak magnetic fields is examined. Tensor components are arranged as powers of the magnetic field up to and including third order terms. Non‐zero expansion coefficients, and the relations between them, are tabulated.
Some Observations on the Cr3+ Fluorescence in the Huntite Structure
Authors: Blasse G. , Bril A. 
Published: July 2007

AbstractAbsorption and emission spectra of Cr3+‐activated huntites of the type Ln3+Me3+3B4O12 (Ln = Y or Eu, Me = Al or Ga) are reported. For the aluminium and gallium compounds the crystal field splitting of the Cr3+ ion is about equal, but the electrostatic interaction parameter B is different. The Cr3+ emission of these compounds, unlike the emission of ruby, consists of lines and bands. In EuAl3B4O12:Cr, nonradiative energy transfer from Eu3+ to Cr3+ is observed; in YGa3B4O12: Cr nonradiative energy transfer occurs from the host lattice (probably GaO6 groups) to Cr3+.
Mössbauer Effect in Iron‐Aluminium Alloys (I)
Authors: Cser L. , Ostauevich J. , Pál L. 
Published: July 2007

AbstractThe ordering process and magnetic structure of iron‐aluminium alloys near the composition Fe3Al are studied experimentally by the Mössbauer technique. It is found that the isomer shift shows a pronounced hysteresis in the temperature range 750 to 850 °C which indicates the first order character of the B2‐type ordering. The simultaneous appearance of the central (paramagnetic) and hyperfine lines in the temperature interval 640 to 500 °C shows that the Mössbauer spectrum is a superimposition of two spectra. These originate from Fe57 nuclei on two different sublattices; one of them is paramagnetic (A sublattice) and the other is magnetically ordered (D sublattice). The hyperfine field and the isomer shift of the hyperfine lines show a pronounced discontinuity at the temperature of the DO3‐type ordering. At this temperature it is found the intensity ratio of the outer to adjacent peak also suffers a sudden change. This indicates a ferromagnetic to antiferromagnetic transformation which is not contrary to existing theoretical ideas but as yet lacks direct experimental confirmation.
Interaction of Optical Phonons with Spin Waves in Ionic Crystals
Authors: Casselmann T. N. , Spector H. N. 
Published: July 2007

AbstractOptical phonon effects on the magnon resonance (FMR and AFMR) are shown to be negligible in ferromagnetic insulators and most antiferromagnets in present day laboratory fields (H ⪅ 2 × 105 G). In these fields the magnon frequency lies lower than the optical phonon frequency so that the coupling is to a polarization mode which is mainly photon‐like. However, at the band edge, the wavelength‐dependence of the magnon and optical phonon dispersion may allow crossing in low fields. Also, in metamagnetic systems where the anisotropy field is much larger than the exchange field, the resonance in the paramagnetic phase may occur in a frequency range such that the polarization mode will contain a relative large fraction of optical phonons. The theory developed in this paper can also be applied to optical phonon‐spin resonance in paramagnetic salts. This type of resonance should occur in attainable magnetic fields for materials with large g factors.
Wavy Fringes at Domain Boundaries in Barium Titanate Observed in the Electron Microscope
Authors: Remaut G. , Gevers R. , Amelinckx S. 
Published: July 2007

AbstractA series of numerically calculated fringe profiles shows that images of zig‐zag fringes superposed on wavy fringe patterns in BaTiO3 result from three superposed ferro‐electric domain walls. The two outer walls being 90° boundaries, while the central interface is a 180° boundary which, in order to decrease the electrostatic energy, “meanders” between the two 90° walls.
Über das Kriechverhalten von NaCl‐Einkristallen
Authors: Blum W. , Ilschner B. 
Published: July 2007

AbstractDie stationäre Kriechgeschwindigkeit von NaCl‐Einkristallen wurde in Abhängigkeit von der Temperatur, der Belastung und dem Verformungsgrad im Druckversuch gemessen. Die Auswertung stützt sich vor allem auf eine theoretisch begründete Darstellung der Meßwerte als log (dε/dt) = f(ε). Dynamisches Gleichgewicht zwischen Verfestigung und diffusionsgesteuerter Erholung (Klettern von Stufenversetzungen) vermag das beobachtete Verhalten zu deuten. Wesentliches Element der quantitativen Auswertung der Kriechversuche (mit und ohne Schmierung durch Glasfolien) ist die Berücksichtigung der Probenformänderung während der Verformung.
Electron Spin Resonance of Co2+ Ions in Barium Titanate
Authors: Žďanský K. , Arend H. , Kubec F. 
Published: July 2007

AbstractThe ESR of Co2+ ions in the slightly deformed octahedral field of BaTiO3 single crystals is observed. The values of the isotropic parts of the g‐factor and the hyperfine parameter A are determined from the spectra. The effect of thermal treatment in oxygen and hydrogen atmospheres is observed. The measured values of the g‐factor and of the hyperfine parameter A are discussed and compared with the values of these parameters in MgO crystals.
The Theory of Stability during Temperature Gradient Zone Melting
Authors: Delves R. T. 
Published: July 2007

AbstractFirst, a dynamic theory is given for the stability of a melting interface when there is a segregating component. Stability during temperature gradient zone melting is analysed to first order in the amplitude of the intial disturbance, assuming infinite thermal conductivity. This case is also discussed with the addition of nucleation kinetics at the interfaces, and slowly developing instabilities are found in most cases. Thermal effects are included and are found to modify but not remove the instabilities whose wavelength is longer than the zone thickness. However, if the wavelength is shorter than the zone thickness an instability may develop rapidly unless the interface free energy is sufficient to stabilize the interfaces. This conclusion has been found previously by Seidensticker. The conditions for avoiding the fast instability are thin zones and small temperature gradients.
Luminescence of CdS Excited by Electrons of Various Energies
Authors: Egorov V. D. 
Published: July 2007

AbstractLuminescence spectra of spontaneous and stimulated emission are investigated for CdS‐crystals excited by electrons with energies between 15 and 150 keV at liquid nitrogen temperature. Selfabsorption is shown to affect the spectral distribution of the radiation from the excited surface. The dependence of the luminescence intensity on the beam current density is measured.
Observations of Ferromagnetic Domains by Anomalous Transmission of X‐Rays. The Effects of Variation in the Reflecting Plane
Authors: Roessler B. 
Published: July 2007

AbstractThe ferromagnetic domain patterns observed by anomalous transmission of X‐rays in Fe–3% Si crystals grown by secondary recrystallization are shown to depend on the choice of reflecting plane. The {110} reflection shows straight lines in the 〈100〉 directions which are sometimes resolved as zig‐zag lines. The {200} reflections show surface closure domains which are the same as those seen in Bitter patterns; zig‐zag boundaries and several other features are also seen. The importance of strain effects in determining the domain pattern is discussed.
Magnetic Properties of NaNiF3
Authors: Judin V. M. , Sherman A. B. 
Published: July 2007

AbstractThe static magnetic properties of a single crystal of NaNiF3 (space group Pbnm) are investigated in the temperature range 77 to 300 °K. The Néel temperature, TN = 156 °K, is determined and the temperature dependences of the magnetic susceptibilities along different crystallographic directions are investigated. The spontaneous magnetic moment is observed only along the c‐axis in fields of up to 18 kOe at 77 °K. The results obtained are discussed within the framework of the thermodynamic theory of weak ferromagnetism. The anisotropic superexchange appears to be most probable mechanism for the origin of weak ferromagnetism in NaNiF3. A departure of the temperature dependence of the spontaneous moment from the respective Brillouin function is observed.
Investigation of the Quasi‐Local Level in the Vibrational Spectrum of the Ti Lattice with Heavy Impurity Atoms
Authors: Chernoplekov N. A. , Panova G. Kh. , Zemlyanov M. G. , Samoilov B. N. , Kutaitsev V. I. 
Published: July 2007

AbstractA quasi‐local level appears in the vibrational spectrum of a titanium lattice containing 5 at % of uranium. This is investigated both by neutron inelastic scattering techniques and by measuring the low‐temperature heat capacity. The results obtained are found to be in satisfactory agreement with theoretical calculation.
On the Mechanism of Thermal Conductivity in (GaSb)3x–(Ga2Te3)1–x and (GaSb)x–(GaTe)1–x Solid Solutions
Authors: Abdurakhmanova A. A. , Aliev M. I. 
Published: July 2007

AbstractMeasurements are made of the thermal conductivities of (GaSb)–(Ga2Te3)1–x and (GaSb)x–(GaTe)1–x Solid Solutions as a function of composition and temperature (80 to 550 °K). Decrease of x as a function of composition is caused by the strong scattering of phonons on the distortion of lattice periodicity and defects. The thermal resistance is produced by 3‐phonon processes. In the alloys with high concentration of defects x does not depend on T in the temperature range T > 350 °K. (The mean free path of phonons is li ≦ a, where a is the lattice constant.) The additional thermal resistance observed in all alloys is caused primarily by phonon scattering oil the defects. Provided a linear frequency dependence of the relaxation time of N‐processes good agreement of experimental results with theory is observed.
The Penetration Depth in Two Band Model Superconductors
Authors: Radhakrishnan V. 
Published: July 2007

AbstractThe experimental results of Maxfield and McLean for the variation of penetration depth λL(T) with temperature for niobium cannot be explained in terms of the usual BCS model of superconductivity. It is shown that better agreement can be obtained on the basis of the twoband model, proposed by Suhl, Matthias and Walker, for transition element superconductors.
Veränderungen an reinen Platinoberflächen durch gelöste Fremdstoffe: Beobachtungen mit dem Feldelektronenmikroskop
Authors: Vanselow R. 
Published: July 2007

AbstractIm FEM wurden Spitzen aus spektralreinem Pt bei p < 1 × 10−9 Torr ohne Feld getempert. Unterhalb 500 °C blieb das durch geeignete Vorbehandlungen erzielte Bild der reinen Oberfläche erhalten. Oberhalb 500 °C bewirkten zur Spitzenkalotte diffundierende, aus dem Pt stammende Fremdstoffe Veränderungen. Bis ca. 1350 °C wurde eine reproduzierbare Folge sehr verschiedener Bilder durchlaufen, deren charakteristische Merkmale im wesentlichen von der Spitzentemperatur und meist nur wenig von der einige Minuten betragenden Temperdauer abhingen. Auf Grund bekannter flächenspezifischer Reaktionen bzw. Anlagerungen konnte ein Teil der Merkmale auf die Anwesenheit von Sauerstoff und Eisen zurückgeführt werden. Nach vorliegenden Analysen mit dem Feldionen‐Massenspektrometer ist weiterhin mit dem Vorliegen von Kupfer zu rechnen [1].
Second Order Conductivity and Nonlinear Plasma Excitation of an Isotropic Electron Gas
Authors: Stolz H. 
Published: July 2007

AbstractThe theory of the second order conductivity tensor of an isotropic electron gas is developed using thermodynamic Green's functions. It is shown that this quantity is exactly determined by the first order conductivity tensor and an additional term consisting of a pure three‐current correlation function. This term is found to be small in the optical and plasma regions. The second order conductivity tensor is calculated in the Hartree approximation. The poles of the second order response function relating the induced particle density to a scalar external potential are discussed and shown to yield the second and zeroth harmonics of the ordinary plasma waves as determined by the linear response of the system. For the special case of shock excitation by a Coulomb potential, semiquantitative arguments are presented in favour of a non‐negligible second order contribution to the total density response which may possibly also contribute to the energy loss of fast electrons in metals.
Effect of Current Carrier Scattering on the Complex Dielectric Tensor
Authors: Zyryanov P. S. , Okulov V. I. 
Published: July 2007

AbstractA general expression is derived for the scattering‐dependent complex conductivity tensor σα β(ω, q). The density matrix satisfying the local charge and energy conservation laws in the presence of an electromagnetic field, is calculated in a linear approximation with respect to the carrier‐field interaction. It is shown that the conductivity tensor involves the term Δσαβ which vanishes if either the spatial dispersion or the scattering is not considered. In a high non‐uniform magnetic field at low frequencies the term gives rise to the conductivity current. If the orbital quantization is essential Δσαβ causes the diamagnetic susceptibility to become frequency‐dependent.
Temperature Dependence of Hyperfine Structure Tensors of Diatomic Halogen Centres in Alkali Halide Crystals
Authors: Dreybrodt W. 
Published: July 2007

AbstractThe ESR‐spectra of diatomic halogen centres of the type X and XY− in alkali halides show temperature dependent line positions due to changes of the hfs‐constants. The temperature dependent part of the hfs‐tensors is determined from an analysis of these spectra. The mechanisms leading to the temperature dependence are discussed: crystal lattice vibrations and resonant vibrations of the molecule modulate the crystal field. This lowers the electron density at the nuclei of the molecule as the vibrational amplitude increases. The frequencies of the molecular vibrations are determined from the experimental data. The effect of the lattice on the force constants is discussed with reference to the comparison of these values with those for the corresponding free molecules.
An X‐Ray Diffraction Study of Rubidium Chloride
Authors: Järvinen M. , Inkinen O. 
Published: July 2007

AbstractAbsolute X‐ray intensity measurements are made of Bragg reflexions from rubidium chloride powders at 300 °K by direct measurement of the intensity of the primary beam. It is found that the effects of preferred orientation, surface roughness, and extinction are negligible. Values for the temperature parameters of BRb = (2.28 ± 0.10) Å2 and BCl = (2.44 ± 0.10) Å2 are obtained; these correspond to the Debye temperature Θ = (157 ± 4) °K. The values of the crystal radii of the ions are found to be RRb = (1.71 ± 0.05) Å and RCl = (1.58 ± 0.05) Å. Deviations from spherical symmetry are revealed in the outer electron distribution of the chlorine ions. Throughout the entire angular range examined, the average trend of the experimental scattering factors of both ions is found to coincide with the theoretical free‐ion values to within 1.5%.
Measurement of Thermal Parameters of Thin Films and Plane‐Parallel Plates Located on a Thermally Conductive Base
Authors: Budke O. , Krempaský J. 
Published: July 2007

AbstractA method is developed for measuring the thermal conductivity, thermal diffusivity, and specific heat of thin films and plates located on a thermally conductive base. The method of measurement involves the use of a point or line pulse heat source. Mathematical expressions for the present treatment are derived from the computed solution of the complex transcendental equations. The present method makes it possible to measure the temperature characteristics of samples of thickness h ≧ 10 μm located on a base with a practically arbitrary thermal conductivity and a definite temperature characteristic. However, the computation can easily be extended to include samples of thickness h < 10 μm.
A Possible New Group of Semiconducting Compounds
Authors: George W. P. R. , Goodman C. H. L. , Sterling H. F. , Warren R. W. 
Published: July 2007

AbstractAn extension of the chemical bonding approach to semiconductivity leads to the prediction that certain highly refractory intermetallic compounds could be high mobility semiconductors. Special Czochralski techniques were developed to pull single crystals of titanium and zirconium diboride, which melt in the 3000 °C range. In agreement with the theory, these materials were found to be non‐metallic. The lowest carrier concentration obtained however (6 × 1020 electron/cm3) could not enable a distinction to be made between impurity semiconductor and semimetal particularly as some non‐stoichiometry might be expected from the mode of preparation.
Die elektrischen Eigenschaften von Versetzungen in Germanium
Authors: Schröter W. 
Published: July 2007

AbstractDie Hallkonstante plastisch verformter, schwach p‐dotierter Germaniumeinkristalle wurde zwischen 50 und 250 °K gemessen. Die elektrisch wirksamen Verformungszentren konnten als Versetzungen identifiziert werden. Während die Trägerdichte bei höheren Temperaturen durch Versetzungsakzeptoren bestimmt ist, beweist die Kompensation chemischer Zentren bei tiefer Temperatur Versetzungsdonatoren. Die Auswertung führt auf ein Versetzungsband, dessen Besetzungsgrenze im neutralen Zustand 0,09 eV über der Valenzbandkante liegt.
Effets galvanomagnétiques et thermomagnétiques classiques dans l'arséniure de cadmium
Authors: Sexer N. 
Published: July 2007

AbstractUne étude classique des phénomènes de transport dans l'arséniure de cadmium, Cd3As2, a permis de choisir un modèle pour la structure des bandes de conduction de ce composé. Ce modèle comporte deux bandes de conduction, distantes de 0,15 eV et de masses effectives 0,06 et 0,12 m.
Optical Studies of β‐SiC
Authors: Ziomek J. S. , Pickar P. B. 
Published: July 2007

AbstractThe results of a study to characterize samples of single crystals of β‐SiC grown by a modified Czochralski technique are given. The X‐ray diffraction patterns were indexed as a face‐centered cubic lattice whose parameter was a0 = 4.357 Å and showed virtually no twinning. The absorption measurements in the region from 1.5 to 4.0 eV yielded an estimate for the band gap for the indirect transition as 2.60 eV which agree with that obtained from photoconductance experiments. In the region from 0.05 to 0.5 eV room temperature absorption measurements showed absorption bands which could be tentatively assigned as two‐phonon bands. Raman spectrum excited by the 6328 Å line of the HeNe laser showed two bands, one at 795 cm−1 taken as the transverse optical mode, and one at 995 cm−1 taken as the longitudinal mode.
The Effect of Grain Size on the Lattice Thermal Conductivity of Copper Aluminium Alloys
Authors: Salter J. A. M. , Charsley P. 
Published: July 2007

AbstractMeasurement of the lattice thermal conductivities between 1.5 and 4.2 °K of a series of CuAl alloys indicates that there is a term linear in temperature which can be attributed to grain boundary scattering of phonons. The results are compared with two approaches to the kinetic model in which a frequency independent relaxation time for grain boundary scattering is assumed. In the first it is assumed that (Kg)−1 = ΣWi, where the Wi are the thermal resistivities due to each scattering process considered alone. In the second a combined relaxation time for all processes is defined by τ− = Σ τ−1. It is shown that in the latter approximation the model describes the experimental results well.