bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dislocation and Crowdion Plasticity of Corundum at Room Temperature
Authors: Rozhanskii V. N. , Nazarova M. P. , Svetlov I. L. , Kalashnikova L. K. 
Published: July 2007

AbstractDuring concentrated load deformation of corundum basal plates at room temperature dislocations are formed near the impression in (0001), {1120}, and {1211} planes. However, these dislocations near the impression are not numerous. Thus the formation of an impression of the indenter cannot be ensured by such dislocations. In this case, according to Indenbom's hypothesisReported at the Conference on Deformation Strengthening of Crystals, held in Kharkov, October 13 to 16, 1969.
, the substance from under the indenter can be outflowed by dynamic crowdions. The deformation of a crystal is essentially accomplished at the expense of origination of dynamic crowdions running in the 〈1100〉 directions in which oxygen ions are close packed. As a result this region of the crystal is enriched by interstitial oxygen ions. During heating of the crystal a coagulation of interstitial ions takes place and a great number of dipoles and loops appears around the impression in (0001) and {1100} planes. The Burgers vector of the loops is \documentclass{article}\pagestyle{empty}\begin{document}$ b = \frac{a}{3}\left\langle {1\bar 10\frac{c}{a}} \right\rangle $\end{document}.
A Pseudopotential Approach for the Green's Function of Electrons in Amorphous Solids
Authors: Kramer B. 
Published: July 2007

AbstractAn approximative expression for the averaged Green's function of an amorphous structure with short‐range order is presented. The main assumptions incorporated are that the atomic potential can be represented by a model potential as used in pseudopotential calculations of electronic properties of crystals, and that the amorphous structure can be described by a product of two‐particle correlation functions. A complex energy function is introduced which describes the main features of the averaged Green's function. It can be calculated by solving a modified pseudopotential equation. Using the complex energy spectrum the density of states is calculated as a “lifetime” broadened crystalline density of states.
A Statistical Theory of Solid Solution Hardening
Authors: Labusch R. 
Published: July 2007

AbstractThe critical shear stress τc to move a dislocation through a random array of obstacles in the glide plane is calculated using a statistical theory. The result is an expression for τc in terms of the obstacle concentration, the line tension of the dislocation, and of the interaction force between the dislocation and a single obstacle. Fleischer's solution of the same problem is not reproduced by the statistical theory. Quantitatively the two results are not very different, but our new result is supported by some recent experimental evidence. Furthermore the theory provides a definite prescription how to combine the concentrations and interaction forces of obstacles of different kinds in the expression for τc.
Dynamic Pinning Induced by Nickel Layers on Permalloy Films
Authors: Hoffmann F. 
Published: July 2007

AbstractThe dynamical pinning induced by thin layers of nickel on epitaxial permalloy films is investigated by stationary spin wave resonances at 17 and 35 GHz. The effective surface anisotropy is determined by comparing the location of resonance peaks for films without layer and for composite films. The high value and the d.c. field dependence of the effective surface anisotropy are attributed to the presence of exchange coupling between the films.
Spontaneous Raman Scattering by Polaritons. I. General Theory
Authors: Obukhovskii V. V. , Ponath H. , Strizhevskii V. L. 
Published: July 2007

AbstractA general theory of Raman scattering (RS) by polaritons in anisotropic crystals with an arbitrary number of phonon branches is developed. A classification of possible scattering variants is given for both uniaxial and cubic crystals. Formulas defining the angular dependence of the integral intensity and scattering line shape are obtained. Some possible ways of determining the ratios of electronic—ionic and pure electronic contribution to the RS intensity are discussed. The scattering intensity by longitudinal phonon is also investigated.
Spontaneous Raman Scattering by Polaritons. II. The Case of CdS and LiNbO3 Crystals
Authors: Obukhovskii V. V. , Ponath H. , Strizhevskii V. L. 
Published: July 2007

AbstractOn the base of a general theory of Raman scattering (RS) by polaritons, previously developed by the authors, polariton RS in CdS and LiNbO3 crystals was calculated at scattering radiation with λ1 = 5145 Å and λ1 = 4880 Å, respectively. The angular dependences of RS line integral intensities and besides this for CdS the scattering line shapes were calculated. It is shown in particular that in the CdS scattering spectrum at small angles the auxiliary low‐frequency “photon‐like” line consisting of two similar components should appear besides the usual “phonon‐like” line. In LiNbO3 some scattering variants are studied at the excitation of nine phonon branches of E‐type and of four branches of AI‐type.
Ultramarine study by EPR
Authors: Więckowski A. 
Published: July 2007

AbstractBy EPR, ion‐radicals ˙S−,˙S, and ˙S are found to arise in the process of synthesizing ultramarine. Typical, blue ultramarine contains ˙S ions. At room temperature, the line width is found to be determined to a large extent by spin–lattice interaction, whereas at liquid nitrogen temperature (77° K) almost exclusively by spin–spin interaction. The EPR line shape was analyzed by linear anamorphosis of the resonance curve. The second moment was used for computing the density of polysulfide ions ˙S according to Van Vleck's formula. The results indicate that the ˙S radicals form a face centred cubic lattice in an elementary cell with lattice constant d′ = 2 d = 18.12 Å, where d is the lattice constant of the elementary cell determined by the X‐ray method.
An electron spin resonance study of photoproduced trivalent iron and divalent vanadium in silver chloride
Authors: Cheema S. U. , Smith M. J. A. 
Published: July 2007

AbstractA method is described which allows Fe2+ and V3+ to be formed in the same specimen of silver chloride. Exposure to blue or to red light produces Fe3+ and V2+. The effect of blue light is explained in terms of hole capture by Fe2+ and electron capture by V3+ whereas that of red light is explained in terms of a charge‐transfer absorption by the trivalent forms of iron and vanadium. A re‐arrangement in the environment of Fe3+ occurs on warming to about 203° K. After blue irradiation at 93° K some of the V2+ is believed to be associated with two silver‐ion vacancies. A re‐orientation of the vacancies is observed on warming to about 110 and at about 150° K a further re‐orientation takes place and one vacancy is removed. Photoproduced Fe3+ and V2+ are stable at 93° K. At room temperature they decay at the same rate with a half life which is of the order of minutes.
Inelastic neutron scattering investigation of spin waves and magnetic interactions in α‐Fe2O3
Authors: Samuelsen E. J. , Shirane G. 
Published: July 2007

AbstractSpin waves in antiferromagnetic α‐Fe2O3 have been studied at temperatures of 240 and 290° K by means of inelastic neutron scattering. We report here the first determination of the acoustical branch throughout the entire Brillouin zone and the first observation of the optical branch. The latter shows little dispersion throughout the zone, and has an energy of 1125° K (97 meV) at the zone centre. At the zone boundaries a gap of 20 to 70° K exists between the two branches. Heisenberg interaction parameters Jm defined through a Hamiltonian \documentclass{article}\pagestyle{empty}\begin{document}$ H\, = \, - \,\sum\limits_{i,j} {J_m } (r_{ij} )S_i \cdot S_j $\end{document} were obtained through fitting of the data to theoretical expressions for the dispersion relations. The following values were obtained for the first five nearest neighbours: J1 = 6.0 ± 1.6° K, J2 = 1.6 ± 0.6° K, J3 = −29.7 ± ± 2.0° K, J4 = −23.2 ± 1.0° K and J5 = −1.0 ± 1.0° K. Interactions to farther neighbours were found to be weak. Neutron intensity data were partly invoked in obtaining the interaction parameters, as two sets of parameters could fit the energy data almost equally well, but they predicted different relative intensities for the two branches in certain regions of the reciprocal space. All spin waves of energy larger than 80° K, including the entire optical branch, were found to be unaffected by the Morin spin‐flip transition at 261° K temperature. The spin‐wave data were used to calculate the sublattice magnetization, the Néel and the Curie‐Weiss temperatures, the perpendicular susceptibility at low temperatures and the density of spin‐wave state spectrum.
Diffusionsanisotropie in Eisen–Silizium‐Legierungen
Authors: Forsch K. 
Published: July 2007

AbstractDie magnetfeldinduzierte Anisotropie wurde an FeSi‐Einkristallen mit 4,2; 6,7; 9,8 und 14 At% Si untersucht. Zwischen 50 und 350°C zeigt die Diffusionsanisotropie sowohl in [100]‐ als auch in [110]‐Richtung fast die gleiche Abhängigkeit von der Meßtemperatur wie die Kristallanisotropie. Die Zeitabhängigkeit der in einer Probe mit 4,2 At% Si in [100]‐bzw. [110]‐Richtung induzierten Anisotropie läßt sich gut durch eine einzige Relaxationszeit mit τ0 = 3 × 10−14±1.5 s und Q = (2,35 ± 0,2) eV beschreiben. Die Kristalle mit höheren Si‐Gehalten zeigen ein komplizierteres Verhalten.
Experimental verification of the theoretical model for the photoionization of deep impurity centres in semiconductors
Authors: Zavadskii Yu. I. , Kornilov B. V. 
Published: July 2007

AbstractThe wavelength dependence of the photoionization cross‐section (PCS) of the Zn acceptor level at Ev + 0.31 eV in silicon has been determined for temperatures of 85 and 290 °K from an investigation of the photoexcitation of holes from this level into the valence band. The experimental results are compared with the theoretical predictions based on a deep‐centre model using a short‐range potential. The agreement between theory and experiment is reasonable.
Fine structure of weak kinematical diffraction beams emerging from wedge‐shaped crystals
Authors: de Ridder R. , van Landuyt J. , Gevers R. , Amelinckx S. 
Published: July 2007

AbstractThe fine structure of a weak kinematical diffraction beam, due to the presence of a wedge shaped crystal part in the selected area, is derived by applying a Fourier transformation to the expression of the wave function deduced within the two‐beam kinematical theory. Also the correspondence between the fine structure of a weak beam and the dark field image, produced by this beam, is analysed. Two general types of wedges are considered: wedges formed by grain or twin boundaries and general genuine wedges bound by vacuum. The theoretical results for the fine structure caused by the two types of wedges are compared with experiments on twin boundaries in stainless steel and on MgO crystals. The observations are in very good agreement with the theory.
Effect of pressure on the curie points of the pseudo‐NiAs‐type Mn1+δSn
Authors: Ozawa K. , Ogawa M. , Yanagisawa S. , Anzai S. 
Published: July 2007

AbstractCurie temperatures of Mn1+δSn, including interstitial Mn atoms in NiAs‐type structure, have been investigated using the magnetic induction method at hydrostatic pressures up to about 5 kbar. The magnetic induction smoothly diminishes at Tc (250 to 260 °K). No transition anomaly has been observed in electrical resistivity of Mn1.77Sn and Mn1.5Sn quenched from about 700°C. The values of specific resistivity are observed to be (4 ± 1) × 10−4 Ωcm at room temperature. The Curie temperatures increase linearly with increasing pressure at the rates of dTc/dp: +(2.0 ± 0.1) deg/kbar, +(1.5 ± 0.1) deg/kbar, and +(1.2 ± 0.1) deg/kbar for Mn1.77Sn quenched from 710, 480, and 380°C, respectively, and +(1.9 ± 0.1) deg/kbar for Mn1.5Sn quenched from 700°C. The positive pressure effect indicates that the exchange interaction is enhanced by decreasing the volume in Mn1+δSn. This deduces that the shift of Tc due to change of quenching temperature is explicable in terms of the volume effect of exchange interactions. It is also found that dTc/dp strongly depends on the quenching temperature, i.e. the ordered arrangements of Mn interstitial atoms, although little difference has been observed in dTc/dp between δ = 0.5 and 0.77 quenched from about 700°C.
Thermal expansion and volume change of crystals containing substitutional point imperfections
Authors: Timmesfeld K. H. , Elliott R. J. 
Published: July 2007

AbstractThe change in volume and thermal expansion coefficient of a crystal by the introduction of point defects is investigated. These effects have three contributions: 1. a change in the spring constants around the defect, 2. a change in anharmonicity around the defect, 3. the changed normal modes of the crystal containing defects. These three contributions partly cancel so that the resulting change in thermal expansion coefficient may be positive or negative. Especially in the case of the occurrence of a low frequency resonance a dip or bump in the low temperature region of the thermal expansion coefficient may occur.
Fine Structure of Electronic Spectra of Binary Substitutional Alloys in a Single‐Band Model
Authors: Čápek V. 
Published: July 2007

AbstractThe fine structure of the electronic density of states due to clusters of impurity atoms in disordered binary alloys is studied for a single‐band model with a short‐range random scattering potential. The sum of the n‐centre contributions to the total T‐matrix is obtained for n = 1, 2, 3. The T‐matrix describes the scattering corrections to an optimum one‐centre approximation which is determined self‐consistently in each case. For n = 1, the method is identical with the coherent potential approximation (CPA). Comparison of the results for n = 1 and n = 2 gives a criterion for validity of the CPA. A simple one‐dimensional model is studied numerically in the two‐centre approximation and the results are compared with the CPA and the direct solution for a finite chain.
Neutron Diffraction Study of Ni(OH)2
Authors: Szytula A. , Murasik A. , Balanda M. 
Published: July 2007

AbstractA synthetic polycrystalline sample of Ni(OH)2 was investigated by means of neutron diffraction in the temperature range 4.2 to 293 °K. The crystallochemical structure of this compound is analogous to the structure of Ca(OH)2. At temperatures below 28 °K Ni(OH)2 is antiferromagnetic with magnetic moments directed parallel to the c0‐axis.
Relativistic Energy Bands of HgTe and HgSe
Authors: Overhof H. 
Published: July 2007

AbstractThe electronic band structures of HgTe and HgSe have been calculated using the relativistic Green's function method. The results are compared to reflectivity data. Particular care was taken to calculate the details of the band structure in the vicinity of the band gap. A valence band overlap is found which is in agreement with the estimate given by Vérié.
The F Center in KCl Crystals Part I: Formation and Bleaching Kinetics
Authors: Aegerter M. A. , Lüty F. 
Published: July 2007

AbstractA quantitative analysis of the higher transitions of the M center in the UV up to 5.0 eV in KCl crystals with high [M] : [F] ratio and unaligned and aligned M centers shows several new excitations (“LM bands”). Assuming that the LM excitation leads to conductive states, a simple electron kinetic model shows that UV irradiation of the F + M center system produces ionized F and M centers (α and F) while competing capture processes partially destroyed them or form F' and M' centers. The F center production spectrum should closely follow the absorption ratio of LM:LF while the bleaching spectrum should follow the F' and M' spectrum. Experimental confirmation of this model is presented. By X‐raying the crystal (containing F + M centers) at LHeT, extra electron traps are introduced into the crystal and shift the equilibrium of the reaction to higher amount of F center, which are not stabilized by F' and M' centers. These extra F centers anneal out near 40 °K in parallelity with the third stage annealing of X‐ray produced α‐centers‐interstititals anions.
The Magnetic and Structural Properties of Bulk Amorphous and Crystalline Co‐P Alloys
Authors: Simpson A. W. , Brambley D. R. 
Published: July 2007

AbstractBulk samples, of the order 0.2 mm thick, of cobalt‐phosphorus alloys have been prepared by prolonged electroless deposition with phosphorus contents varying from 5 to 9 at%. Alloys with less than 8.8 at% were found to be crystalline with a single‐phase h.c.p. structure, and those with 9 at% were amorphous. The saturation magnetization, magnetostriction, coercivity, and susceptibility of the crystalline alloys varied uniformly with phosphorus content. The amorphous alloys had significantly different magnetic properties from the crystalline ones of similar composition; in particular the susceptibility was nearly two orders of magnitude greater. This greater susceptibility was predominantly associated with the absence of magnetocrystalline anisotropy in the non‐crystalline material. On annealing, the amorphous material first transformed to a single‐phase h.c.p. structure similar to that of the crystalline alloys, and at a higher temperature to the equilibrium two‐phase structure of a cobalt‐rich h.c.p. phase and an orthorhombic Co2P phase. The susceptibility of the amorphous alloy fell by a factor of 15 times on annealing. This was attributed to the introduction of crystalline order and hence magneto‐crystalline anisotropy.
Behaviour of Primary Defects in Electron‐Irradiated Germanium
Authors: Bourgoin J. , Mollot F. 
Published: July 2007

AbstractAn investigation is made of the influence of the free electron and donor impurity concentrations on the annealing kinetics of the 35 and 65 °K stages and on the creation rate of the 35 °K stage, in low temperature electron irradiated n‐type Germanium, using As‐ or Sb‐doped samples, Ga and Cu compensated samples, and a Li‐doped sample. The results obtained allow to conclude that the mobility of the Ge interstitial occurs at 4.5, 27, and 65 °K, depending on its charge state and the mobility of the vacancy at 90 °K, and to identify the defect associated with the 35 °K stage as a vacancy‐interstitial pair where the interstitial is a donor impurity (annealing through the interstitial mobility). This interstitial mobility, strongly dependent on the charge state, explains radiation annealing and the behaviour of irradiated p‐type Germanium.
Magneto‐Reflectivity Measurements on Exciton Bands in CuCl
Authors: Staude W. 
Published: July 2007

AbstractThe influence of an external magnetic field on the normal incidence reflectivity of CuCl single crystals has been measured in the Voigt and Faraday configurations. The results are discussed in terms of the dielectric function calculated from the reflectivity spectrum by a Kramers‐Kronig transformation. In the Voigt configuration two new exciton bands can be observed, which are attributed to a triplet and a longitudinal exciton. Their energetic positions are used to determine the parameters of electron‐hole exchange interaction in the 1s excitons, and the spin‐orbit splitting parameter of the upper valence band. The excitonic g‐values are determined from the Faraday configuration measurements and can be interpreted on the basis of the tight binding model.
Stress Relaxation Testing and the Determination of the Internal Stress
Authors: Lloyd D. J. , Embury J. D. 
Published: July 2007

AbstractThe use of stress relaxation methods to establish the parameters describing dislocation mobility have been critically examined. It is shown that the values of internal stress established from the condition of zero relaxation rate are temperature independent and equivalent to the athermal component of the flow stress. The various methods of establishing the internal stress are in accord providing cogniscence is taken of the experimental limitations of the technique.
Magnetostriction of Antiferromagnetic Cr2O3 in Strong Magnetic Fields
Authors: Dudko K. L. , Eremenko V. V. , Semenenko L. M. 
Published: July 2007

AbstractThe magnetostriction of antiferromagnetic Cr2O3 has been measured in a magnetic field directed along the crystal symmetry axis. In the field H
c = 60 kOe which corresponds to a spin‐flip transition we have observed jumps in the crystal sizes. The deformation along the symmetry axis is 2.8 × 10−5 and the relative volume change is 2.0 × 10−5. The form of the magnetostriction curves may be accounted for by the dependence of magnetic anisotropy energy on the interatomic distances. The calculation of magnetic dipole interaction in the given crystal provides jump values which are considerably lower than those observed. The contributions to the magnetic anisotropy energy arising from considering the spin‐orbit coupling are assumed to be important for magnetoelastic properties of Cr2O3.
Second‐Harmonic Generation and the Ordering Reaction in NH4Cl
Authors: Bartis F. J. 
Published: July 2007

AbstractThe order‐disorder transformation in ammonium chloride is taken to be a first‐order phase change. The asymptotic behavior of the second‐harmonic intensity is determined on the assumption that the growth of the ordered domains is controlled by the stress field around crystal defects. By a suitable choice of the characteristic temperature T0 the data can be reconciled with nucleation along edge dislocations. The location of T0 relative to the hysteresis region suggests that the irreversibility of the transition is associated with the formation of vacancies.
Thermal expansion, heat capacity, and compressibility of solid CO2
Authors: Manzhelii V. G. , Tolkachev A. M. , Bagatskii M. I. , Voitovich E. I. 
Published: July 2007

AbstractThe coefficients of thermal expansion (13 to 139 °K), heat capacity (2 to 20 °K), and velocity of longitudinal and transversal ultrasonic waves (88 to 190 °K) for solid CO2 have been determined along the solid‐vapour equilibrium line. Heat capacity of constant volume, adiabatic and isothermal compressibilities, the Grüneisen and Poisson coefficients were calculated using the above data. The contributions of various types of heat motion to heat capacity, thermal expansion and compressibility have been separated, and the parameters of isolated orientational defects in crystalline CO2 determined. The connection between the orientational defect parameters and the extent of non‐centricity of intermolecular interactions in solids is discussed.
Influence of electron‐electron scattering on the anisotropic conductivity at high electric fields in Si
Authors: Asche M. , Boichenko B. L. , Bondar V. M. , Sarbei O. G. 
Published: July 2007

AbstractThe conductivity and its anisotropy were investigated in dependence on the electric field strength in a wide range of impurity density for n‐Si at 77 °K. It is shown that the intervalley transfer of electron energy on account of electron‐electron interaction has to be included for carrier densities above 1015 cm−3 in order to achieve a satisfactory description of the results obtained experimentally.
Density of states in ordered and disordered ferromagnetic thin films
Authors: Goedsche F. 
Published: July 2007

AbstractThe density of spin‐wave states in ordered and disordered linear Heisenberg chains is investigated. The disorder is introduced by setting random quantities for the exchange integrals. The model also includes the effect of surface spin pinning and variations of the exchange integrals near the film faces upon the spectrum. Surface modes as well as the bulk spectrum for both types of order are discussed.
Torsional vibrations of H2O molecules in crystalline Li2SO4·H2O
Authors: Janik J. M. , Janik J. A. , Pytasz G. , Wasiutyński T. 
Published: July 2007

AbstractResults of IR and Raman measurements for Li2SO4·H2O and Li2SO4·D2O are reported and compared with neutron inelastic scattering data. Bands at about 320,580, and 850 cm−1 are interpreted as connected with H2O torsions. A group theory analysis of the torsional vibrations of H2O molecules in the crystal is given.