bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prismatic Slip in Beryllium and the Relative Ease of Glide in H.C.P. Metals
Authors: Regnier P. , Dupouy J. M. 
Published: July 2007

AbstractThe macroscopic C.R.S.S. for prismatic slip in Beryllium is found to increase with increasing temperature in the range −100 to +50 °C while the microyield limit decreases regularly. Slip is initiated on the prism planes from the edge dislocations present in the annealed material. Evidences of a thermally activated locking of screw dislocations are presented. This locking is thought to occur by the usual splitting in the basal plane. The assumption that the a dislocations can also dissociate in the prismatic plane seems necessary to account for the activation of this locking. Possible dissociations in the prismatic plane are proposed; the most probable of them is a → a/3 + 2 a/3. It gives a ribbon of stacking fault corresponding to the transformation of two {1010} h.c.p. “flat planes” into two {112} b.c.c. planes. It is suggested that there is a relationship between the energy of the stacking fault on the prismatic plane and the temperature of the phase transformation h.c.p. → b.c.c. This relationship permits to account for the relative ease of slip in h.c.p. metals.
Magnetic Properties of the Hexagonal Iron Nitride ϵ‐Fe3.2N
Authors: Eickel K. H. , Pitsch W. 
Published: July 2007

AbstractThe Mössbauer effect has been measured on powder samples of the h.c.p. iron nitride ϵ‐Fe3.2N at 295 °K. The measurements indicate, that there are two kinds of Fe‐atoms with different environments in this material. This is in accordance with previous X‐ray investigations by which it was found that in ϵ‐iron nitrides the N‐atoms are highly ordered in such a way that e.g. in ϵ‐Fe3.2N the Fe‐atoms have either one or two N‐atoms within their nearest neighbourhood. Furthermore the average magnetic moment of the Fe‐atoms in ϵ‐Fe3.2N has been measured to be 1.97 μB. Using this value together with the Mössbauer data the magnetic moments of the Fe‐atoms are estimated. The moments obtained are 2.4 μB and 1.9 μB respectively. These values are interpreted by similar considerations by which the magnetic structure of the f.c.c. γ′‐iron nitride Fe4N has been explained previously in the literature.
Infrared Piezoabsorption of Silicon in the Multiphonon Spectral Range
Authors: Lüth H. 
Published: July 2007

AbstractPiezoabsorption measurements have been performed on silicon in the multiphonon spectral range (500 to 1000 cm−1). Uniaxial stress along [100] is applied and the light is polarized parallel and normal to the stress axis (‖ and ⟂ [100]). The change of the absorption constant induced by hydrostatic pressure is calculated from the results. Sign and location of the piezoabsorption bands yield a topological classification for the critical points which give rise to the two‐phonon absorption structure in silicon.
Dislocations in Extruded β′‐NiAl
Authors: Lloyd C. H. , Loretto M. H. 
Published: July 2007

AbstractPolycrystalline NiAl which had been plastically deformed at a high temperature has been examined using transmission electron microscopy. It is shown that, in addition to the dislocations of b = 〈100〉, which have been identified by other workers, dislocations of b = 〈110〉 and 〈111〉 contribute to the high temperature plasticity.
Electron Microscopic Study of the Substructure of VO2 due to the Monoclinic to Tetragonal Phase Transformation
Authors: Hayashi Y. , van Landuyt J. , Amelinckx S. 
Published: July 2007

AbstractVanadium dioxide has a monoclinic‐tetragonal phase transformation at about 70 °C. This transformation can be induced in an electron microscope during observation, and the boundaries between the monoclinic and tetragonal phases are observed by the diffraction contrast at the interfaces. When the tetragonal phase is transformed into the monoclinic one, the crystal is broken up into domains according to the different modes of transformation. The interfaces between the domains are revealed as fringe patterns in the electron micrographs. The tetragonal‐monoclinic transformation boundaries and the different types of domain boundaries in the monoclinic phase are studied by electron microscopy.
Optical Investigation of the Small Polaron in β‐FeSi2
Authors: Birkholz U. , Naegele J. 
Published: July 2007

AbstractThe reflectivity of α‐FeSi2 and also of β‐FeSi2 doped with Co (n‐type) or Al (p‐type) has been investigated for wavelengths between 1 and 25 μm. The results for α‐FeSi2 indicate metallic conduction in this material. The reflectivity of the undoped semiconducting phase β‐FeSi2 can be explained by a fundamental absorption corresponding to a band gap Eg = 0.8 eV and a reststrahlen band. The highest branch of the longitudinal optical phonons is found at 20.6 μm. The reflectivity of p‐FeSi2 can be interpreted using Drude's theory of free carrier absorption. The optical properties of n‐FeSi2 cannot be explained by free carrier absorption. A consistent interpretation, however, is possible in terms of the small polaron picture. Using the experimental data of the de conductivity and its activation energy the reflectivity of n‐FeSi2 can be calculated. There is good agreement with the observed values. These results confirm an analysis of the transport properties of β‐FeSi2 which was presented in a previous paper.
On the Force Exerted upon Continuously Distributed Dislocations in a Cosserat Continuum
Authors: Minagawa S. 
Published: July 2007

AbstractThe force acting on distributed dislocations in a Cosserat continuum is studied and the expressions for the force and force density are given in tensorial form. The increase in the potential energy of the material body, caused by a displacement of distributed dislocations in a certain region of the body, is obtained. The force acting on those dislocations is deduced by differentiating it with respect to the distance through which the dislocations are displaced. The expression for the density of forces is given as follows:
equation image
where sjni is the tensor of dislocation density, ∑ij the symmetric part of stresses, Mjni the couple‐stress tensor, and ηij the incompatibility tensor.
Acoustoelectric Effect in a Strong Ultrasonic Field
Authors: Paranjape V. V. , Joshi S. B. 
Published: July 2007

AbstractAverage energy of electrons in semiconductors may change under the influence of a strong ultrasonic sound wave. If the change is considered as a sum of energies due to the random part and the drifting part of the electron gas, then it is shown that the former part of the energy may decrease (electron cooling) in certain circumstances. The total change in the energy is, however, always positive, but is shown to be negligible for polar materials.
Thermodynamic Functions of Piezoelectric Polarons in Steady Magnetic Field and Cyclotron Resonance
Authors: Klyukanov A. A. , Pokatilov E. P. 
Published: July 2007

AbstractThe sum over piezoelectric polaron states is calculated at weak and strong magnetic fields. Feynman's path integral variational method is used to calculate the thermodynamic functions, i.e. energy, magnetic susceptibility, and specific heat. Cyclotron resonance of piezoelectric polarons is considered and a comparison of theoretical and experimental results is given.
Anisotropy of Electron and Hole Mobilities in Orthorhombic Sulphur Crystals
Authors: Nitzki V. , Stössel W. 
Published: July 2007

AbstractThe anisotropy of the electron and hole mobility in orthorhombic sulphur has been investigated measuring the transit times of optically generated carriers. The sulphur crystals have been grown from a temperature controlled CS2 solution. The hole mobilities at room temperature along the main directions μp[100] = (7.4 ± 0.4) cm2 V−1 s−1, μp[001] = (4.6 ± 0.3) cm2 V−1 s−1, and μp[010] = (2.3 ± 0.2) cm2 V−1 s−1 decrease with increasing temperature like μp[100], [001] ∼ T−3/2 and μp[010] ∼ T−1. Below room temperature the hole mobilities are trap controlled. The electron transport is an activated process governed by the activation energies ϵn[001] = (0.166 ± 0.003) eV, ϵn[100] = (0.157 ± 0.003) eV, and ϵn[010] = (0.153 ± 0.003) eV. The electron mobilities are interpreted in terms of the small polaron theory.
Investigations of Plastically Deformed Copper Single Crystals in the Stress‐Applied State. I. A Study of the Dislocation Behaviour in the Surface Region and in the Bulk
Authors: Mughrabi H. 
Published: July 2007

AbstractCopper single crystals oriented for single glide were deformed in tension at 78 °K to various resolved shear stresses and were then neutron‐irradiated at 4 to 20 °K before stress‐removal in order to pin the dislocations in the stress‐applied state. A comparison of transmission electron micrographs obtained from the centre and the surface regions shows that, from early stage II onwards, the dislocation arrangement in the surface region corresponds to a lower stress than that in the centre. At the same time the dislocation density is distinctly lower in the surface region than in the interior. Furthermore, X‐ray investigations show that during deformation the primary glide plane is bent characteristically near the surface in the direction of the slip vector. Details of these results, which are in good qualitative agreement with flow stress measurements and electron microscope work of Fourie, are discussed and compared with the literature.
Zum Einfluß von Versetzungen auf elektrische Eigenschaften von Natriumchlorid
Authors: Froschauer L. , Ilschner B. 
Published: July 2007

AbstractDie zeitabhängige und die zeitunabhängige elektrische Gleichstromleitfähigkeit von NaCl wurde in Abhängigkeit von der Versetzungsdichte und ‐anordnung gemessen. Es wurde Proportionalität zwischen stationärer Leitfähigkeit und Versetzungsdichte gefunden und auf erhöhte Anionenleitfähigkeit in Versetzungsnähe zurückgeführt. Bei Anlegen der Spannung wurden zwei exponentielle Polarisationseffekte gemessen, von denen der langsamere als Oberflächeneffekt, der schnellere als Volumeneffekt gedeutet wird. Verschiedene Mechanismen zur Begründung werden diskutiert.
Absorption of Ultrasound in Intrinsic Ge, GaSb, and InSb
Authors: Groubert E. , Joullie A. M. 
Published: July 2007

AbstractAn investigation is made of the change of the attenuation coefficient of ultrasonic longitudinal waves with frequencies of 10 to 300 MHz, propagating in monocrystalline Ge. GaSb, and InSb at temperatures of 300 and 77 °K. The measurements were made using the pulse‐echo technique. The results have been treated by the Sylwestrowicz method and fitted with the theories of absorption of sound by Woodruff‐Ehrenreich and Mason‐Bateman.
Theory of Electron Scattering from an Antiferromagnet. I. Heisenberg Model
Authors: De Wames R. E. 
Published: July 2007

AbstractA calculation of the differential scattering cross sections for scattering of low energy electrons from a Heisenberg antiferromagnet is presented. It is shown that the inelastic and elastic cross sections are proportional to the first and second powers, respectively, of the sublattice magnetization. The derived expressions for the scattering cross sections agree well with recently reported experiments on NiO.
Magnetische Bereiche in Chromtrihalogeniden
Authors: Bostanjoglo O. , Vieweger W. 
Published: July 2007

AbstractDie Breite magnetischer Streifendomänen in CrBr3 und CrJ3 wurde lorentzmikroskopisch zwischen der Curietemperatur und 4 °K bestimmt. Bei tiefen Temperaturen ist die Breite fast konstant, nimmt aber bei Annäherung an die Curietemperatur plötzlich ab. Dieses Verhalten kann durch die übliche Domänentheorie und unter der Annahme A ∼ I gedeutet werden. Hexagonale Domänen wurden nach Anwendung eines Feldes senkrecht zur leichten Achse beobachtet.
Die Bestimmung der Fermifläche von Kadmium aus der Orientierungsabhängigkeit der Periode der Sondheimer‐Oszillationen
Authors: Schwarz H. 
Published: July 2007

AbstractAn einem hochreinen Kadmiumeinkristall mit Widerstandsverhältnis ϱ273 °K/ϱ4,2 °K = 18000 wurden bei 4.2 °K Sondheimer‐Oszillationen in der Feldabhängigkeit des Hallwiderstandes in ihrer Abhängigkeit von der Kristallorientierung gemessen. Die Ergebnisse zeigen, daß der linsenförmige Teil der Fermifläche in der dritten Zone für die an Kadmium beobachteten starken Sondheimer‐Oszillationen verantwortlich ist. Es wurde ein Verfahren entwickelt, mit dem dieser Teil der Fermifläche aus der Orientierungsabhängigkeit der Periode der Sondheimer‐Oszillationen sehr genau bestimmt werden konnte. Die so bestimmte Fermifläche ist rotationssymmetrisch um die hexagonale Achse und stimmt mit den Ergebnissen anderer Methoden gut überein. Die Abweichung vom Modell quasifreier Elektronen ist gering.
Pressure Effects on Zero‐Field Resonance. I. Ge3+ in YVO4 and SeVO4
Authors: Hillmer W. , Urban W. 
Published: July 2007

AbstractThe influence of hydrostatic pressure on the zero‐field resonance frequencies of Gd3+ in some isostructural crystals has been measured directly. A short description of the apparatus is given and first results in the range up to 2 kbar are reported.
Study of the Poole‐Frenkel Effect in CdS Single Crystals
Authors: Kirov K. I. 
Published: July 2007

AbstractAn investigation has been made of the electric field dependence of the probability for thermal emission from traps in CdS single crystals using a method described in [10] for the determination of the trap parameters. Levels with depths of 0.42, 0.20, and 0.11 eV and capture cross‐sections of 1.5 × 10−3, 2 × 10−14, and 1.3 × 10−14 cm2 have been studied. At field variations from 103 to 3 × 104 V/cm, the change of the probability for thermal ionization of the traps expected from Frenkel's theory has not been observed.
Ligand Field Theory Formulation of the Optical and Magnetic Properties of U2 Centres in the Alkali Halides
Authors: Hagston W. E. 
Published: July 2007

AbstractIt is shown that a better theoretical formulation of the properties of the U2 centre in the alkali halides is given in terms of ligand field theory rather than the approach usually adopted, which consists of an application of the techniques employed by Gourary and Adrian [5] in their F‐centre calculations. The general features of the present formulation are discussed in relation to experiment, and future experimental and theoretical investigations suggested which should enable the finer details concerning the validity and usefulness of the approach to be elucidated.
Implications of Ligand Field Theory for Substitutional and Interstitial H Atoms and H− Ions in the Alkali Halides and Alkaline Earth Fluorides
Authors: Hagston W. E. 
Published: July 2007

AbstractIt is shown that the model developed for the U2 centre in the alkali halides [1] is qualitatively successful in accounting for the magnetic properties of substitutional and interstitial hydrogen centres in the alkaline earth fluorides. An interconnection between the present theory and that required in the theory of the hyperfine interaction of F centres in these compounds is also pointed out, as well as a suggestion for utilizing the Löwdin orthogonalization technique as a means of quantitatively estimating covalency effects for the various shells of ligands next to a hydrogen impurity. Following a discussion of the properties expected for U3 centres in the alkali halides, certain possible anomalies in the recent assignment [2] of ESR data to such a centre are pointed out. Finally the optical absorption spectra of U centres are investigated and attention is drawn to the fact that a combination of odd parity vibrations, odd harmonic crystal field components, and covalency effects can make allowed s → s and s → d one‐electron dipole transitions in addition to the usual s→p transitions. The resulting implications are briefly discussed.
Directional Dependence of Extraordinary Infrared Oscillator Parameters of Uniaxial Crystals (I)
Authors: Merten L. , Lamprecht G. 
Published: July 2007

AbstractThe validity of the classical dispersion relation (resonance terms of Lorentzian type) for the reststrahlen range of the extraordinary ir spectrum may also be rigorously verified from the basic equations of lattice dynamics combined with the Maxwell equations. The parameters occurring in the dispersion equations, viz. ϵ∞ (ϑ) (high‐frequency dielectric constant), ωj(ϑ) (dispersion frequencies), 4πϱj (oscillator strengths), and γj(ϑ) (attenuation constants), become however orientation dependent, where ϑ is the angle between wave vector and optical axis. Explicit formulae may be given for the orientation dependence of these parameters. As an example the orientation dependence, especially of the oscillator strengths (neglecting attenuation) of α‐quartz, are calculated numerically and discussed in detail. Recently Onstott and Lucovsky have been investigated experimentally the orientation dependence of oscillator strengths of α‐quartz for two of the branches systematically. In consideration of a first comparison the agreement with the values calculated is very satisfactory.
Transmission Electron Microscopy of Point‐Defect Clusters in Neutron‐Irradiated Metals. I. Copper
Authors: Rühle M. , Häussermann F. , Rapp M. 
Published: July 2007

AbstractNeutron‐irradiated copper has been investigated by means of transmission electron microscopy. The nature of the point‐defect clusters has been determined using stereo microscopy. It is shown that the large defects are predominantly of interstitial type and the small defects of vacancy type. The densities and size distributions of the defects observed in differently pre‐treated and irradiated foils were compared. It was found that only quantitative differences exist. Annealing experiments showed that the defect type and the size distribution of the defects are influenced by the annealing atmosphere.
Interpretation of Self‐Diffusion and Vacancy Properties in Silver
Authors: Mehrer H. , Seeger A. 
Published: July 2007

AbstractRecent measurements of the tracer coefficient of self‐diffusion in silver by Rothman, Peterson, and Robinson are analysed. In conjunction with the data on the equilibrium concentration of vacant sites by Simmons and Balluffi, with the temperature dependence of the isotope effect of self‐diffusion and with quenching experiments a consistent set of vacancy properties is deduced. In the usual notation the following mono‐ and divacancy properties are obtained: E = 0.99 eV, E = 0.84 eV, S = 0.5 k, v≈4 × 1013s−1, E − E = 0.34 eV, and ΔS2v ≈ 2.6 k. These values are in good agreement with annealing experiments.
On Temperature Relaxation in Metals
Authors: van den Sype J. 
Published: July 2007

AbstractThe method of Corbino for measuring the specific heat of metallic filaments is extended to the case where the sample undergoes internal transformations. The resistance oscillations of the ac heated filament are described in terms of a frequency dependent heat capacity and temperature coefficient of resistivity. The theory is applied to vacancy relaxation in metals where the method yields an equilibrium determination of vacancy concentrations and lifetimes. The experimental results of Kraftmakher on the high temperature heat capacity of metals are reinterpreted in light of the present theory.
Light Emission from Impurity Centres and Urbach's Rule
Authors: Lubchenko A. F. , Dudkin S. I. 
Published: July 2007

AbstractAn investigation is made of the shape of the emission spectra due to impurity centres in a solid, taking into account the variation of its quasi‐elastic constants during the phototransitions. A formula for the short‐wavelength edge of the emission spectrum similar to the Urbach expression for absorption is obtained.
An Internal Friction Investigation of Gold‐Rich Gold–Iron Alloys
Authors: Mynard B. A. , Leak G. M. 
Published: July 2007

AbstractThe internal friction properties of five gold‐iron alloys on cooling from 900 °C have been studied. The parameters QR, Δm, τ0, β, and Tp for the Zener peak, which was observed in all the alloys at approximately 400 °C, are discussed. Welch's theory is used to predict values for QD in the alloys. An explanation is given for the observed decrease in Δm on increasing the solute concentration in the two‐phase region; the precipitate is identified as iron. An increase in damping is observed on cooling through the phase boundary; a qualitative explanation is given for this effect.
A Theory of Nonlinear Ultrasonic Wave Amplification in Piezoelectric Semiconductors
Authors: Wonneberger W. 
Published: July 2007

AbstractA theory of nonlinear acoustoelectric wave amplification in an active piezoelectric semiconductor is presented assuming a sinusoidal piezoelectric potential. An analytic solution is obtained for the complex amplitudes of the electron density modulation. From this closed expressions for the nonlinear gain, the renormalized sound velocity, the harmonic generation, and the current saturation are derived and discussed.
Structure magnétique du spinelle antiferromagneétique ZnFe2O4
Authors: Boucher B. , Buhl R. , Perrin M. 
Published: July 2007

AbstractOn a fabriqué et étudié par diffraction de neutrons un échantillon de ZnFe2O4. Ce corps est un spinelle normal. A 10,6 °K l'ordre antiferromagnétique à grande distance s'établit. La maille magnétique (a, a, 2 a) a un volume double de celui de la maille chimique (a, a, a). Trois modèles de structures magnétiques rendent compte des résultats expérimentaux. Les moments sont dirigés suivant les axes [100] et [010]. A 4,2 °K le moment magnétique du Fe3+ est 4,0 μB. On détermine la variation de la valeur du moment en fonction de la température.
Temperature Dependence of the Structure of Liquid Mercury
Authors: Waseda Y. , Suzuki K. 
Published: July 2007

AbstractX‐ray diffraction patterns have been obtained from liquid mercury at −35, 15, and 80 °C. The structure factors obtained are nearly independent on temperature and applied to a discussion of the electrical resistivity using Ziman's [16] theory and the pseudopotential (Animalu and Heine [19] or Evans et al. [18]).
Stress Dependence of the E1 and E1 + Δ1 Transitions in InSb and GaSb
Authors: Tuomi T. , Cardona M. , Pollak F. H. 
Published: July 2007

AbstractA double‐beam wavelength modulation technique has been used to measure the effect of static uniaxial compression along the [111] and [001] directions on the E1 and E1 + Δ1 peaks of the reflection spectrum of InSb and GaSb. The splitting of these peaks under [111] stress and the absence of a splitting for [001] stress confirms the Λ symmetry of the corresponding critical points. From the magnitude of the stress‐induced splittings and shifts of these peaks the hydrostatic and shear deformation potentials of the corresponding gaps have been determined.
Etch Pits and Crystal Structure of Tellurium
Authors: Koma A. , Tanaka S. 
Published: July 2007

AbstractE. TakimotoThe shapes of the asymmetric etch pits produced by slow action of hot sulfuric acid on the cleavage planes of tellurium crystals have been investigated, and a microscopic model is proposed for the formation of the etch pits. The handedness of the spiral chains and the positive direction of the x‐axis of the crystal are determined on the basis of the proposed model. Nuclear magnetic resonance (NMR) has been observed in the same crystals and the observed anisotropy in the chemical shift is in good agreement with the calculated one by Shimizu for both right‐ and left‐handed crystals.
Symmetry Assignments of Two‐Photon Transitions in TlCl
Authors: Fröhlich D. , Staginnus B. , Thurm S. 
Published: July 2007

AbstractThe formalism for the polarization dependence of the two‐photon absorption is extended to include circularly polarized light. Measurements with linearly and circularly polarized light on TlCl allow a unique decomposition of the spectrum into the different symmetry contributions.
Suprastriction in Superconductors
Authors: Kronmüller H. 
Published: July 2007

AbstractBy means of the micromagnetic equations of the superconductivity the deformation of a superconductor below the transition temperature is determined. It is shown that as in ferromagnets the deformation of a superconductor may be divided into spontaneous and forced suprastriction, and the formeffect. The theoretical results are compared with recent experiments.