bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electromultipole Interaction and Paramagnetic Relaxation in Ruby I. EPR Line Shape in Ruby
Authors: Peskovatskii S. A. 
Published: July 2007

AbstractThe concentration dependence of the line shape in ruby is investigated experimentally at frequencies 9000, 11500 (crystal field splitting frequency), and 40000 MHz. Assumption of pure magnetic dipole‐dipole interaction does not explain the experimental results. The line broadening caused by quadrupole‐quadrupole interaction of spin states is calculated using a statistical theory. The calculated and experimental data are in good qualitative and quantitative agreement.
Exciton‐Induced Colour Centre Growth in KBr and KI Crystals at 5 °K
Authors: Kink R. , Liidja G. 
Published: July 2007

AbstractColour centres were created in KBr and KI at 5 °K by ultraviolet irradiation, corresponding to the exciton absorption region, and traced by luminescence methods. In KBr the Frenkel defects (I‐centres) are observed in thermal glow curves, created as a result of the fundamental reaction proposed by Pooley. In KI they are not observed, but F‐, F′‐, and VK‐centres were found in photostimulated luminescence. The dissociation of the migrating excitons at structure defects existing in crystals before irradiation seems to be important at the initial coloration stages in KI.
Theory of the Shift of the F‐Band in Alkali Halide Mixed Crystals
Authors: Logatchov Yu. A. , Evarestov R. A. 
Published: July 2007

AbstractA more accurate treatment of the F‐band shift in solid solutions of alkali halides is presented, based on other than usual approximations. The “local” concentration of the impurity cations near a F‐like centre is obtained as the function of the volume concentration from thermodynamical considerations. The transition energies of Fi‐centres (i = 0, 1, …, 6) are calculated in the model potential approximation. The models of F, F, etc. centres are discussed. The peak position of the F‐band in KCl(Na) with 50% concentration of NaCl is obtained. The results are in good agreement with experimental data. The main results have been published in [1].
On the Validity of Modified Wachtman's Equation for Nonoxide Solids
Authors: Rajagopalan S. 
Published: July 2007

AbstractModifications of the Mie‐Grüneisen equation of state have been used in the evaluation of bulk modulus at different temperatures for various nonoxide solids. It is shown that the estimation can be carried out correctly even when the constants γ and δ are not known. The agreement of the calculated values with the experimental ones are satisfactory enough that the modified Wachtman equation can be safely used to estimate the bulk moduli of solids even at temperatures inaccessible to direct experiment.
Investigation of the Lattice Dynamics of KBr: Sm2+ by Means of Vibronic Spectra
Authors: Kühner D. , Wagner M. 
Published: July 2007

AbstractA low‐symmetry (C2 v) model of the lattice disturbance in the system KBr:Sm2+ is employed to calculate the vibronic sideband structure of a 4f‐4f transition. The result yields improvement over earlier calculations, which were based on higher‐symmetry models. The improvement is such that the chosen model may be considered to be realistic.
The Influence of Temperature on Slip Behaviour of Molybdenum Single Crystals Deformed in Tension in the Range from 293 to 573 °K
Authors: Richter J. 
Published: July 2007

AbstractCylindrical molybdenum single crystals of middle orientation (Schmid factor ≈ 0.5 on the (101) [111] slip system) grown by electron zone melting were deformed in tension at various temperatures between 293 and 573 °K using a strain‐rate of 7 × 10−6s−1. Stress‐strain curves are parabolic in shape below 340 °K (T< 0.12Tm), whereas they are clearly divided into three work‐hardening stages above 400 °K (0.14Tm<T< 0.20Tm). The variation of yield stress and work‐hardening parameters in dependence on deformation temperature is systematically investigated and the results are discussed with respect to published work on other b.c.c. metals. Furthermore, molybdenum crystals with various specially chosen “single slip” orientations were deformed at 493 °K. It is found that under these conditions the orientation has no pronounced influence on the stress‐strain curve.
The Mobility of Grown‐in Dislocations in the Intermetallic Compound MgZn2 I. Stress Dependence for Edge Dislocations in Prism Slip at 390 °C
Authors: Paufler P. , Marschner J. , Schulze G. E. R. 
Published: July 2007

AbstractThe velocity x of grown‐in (1010) 〈1210〉 edge dislocations in the intermetallic compound MgZn2 has been measured as a function of stress τ at 390 °C. Dislocation displacements produced by compression pulses were detected by etch pitting (0001) surfaces. The fraction of mobile dislocations ϱm/ϱtot has also been determined as a function of stress. The results indicate that the velocity depends exponentially on τ−1. They are analyzed in terms of a modified kink model after Celli et al‥ Microscopic measurements are in good agreement with stationary creep data.
Experimental Determination of the Shielding of Crystal Fields at Rare‐Earth Ions
Authors: Pistor W. 
Published: July 2007

AbstractBy comparing crystal field parameters A〈rk〉 of Er3+ in ScCl3 and InCl3 with those of Cr3+ and V3+ in the same host lattices, experimental values for the shielding factors σ2and σ4 are determined. The values of σ2between 0.57 and 0.72 are in good agreement with the theory, whereas the values of σ4 between 0.71 and 0.79 do not agree at all with the theoretical values. Possible interpretations for the differences are given.
The Temperature Dependence of Slip Planes in Fe‐3.4% Si Single Crystals
Authors: Šesták B. , Blahovec J. 
Published: July 2007

AbstractThe temperature dependence of macroscopic slip planes observed on tension and compression sides of specimens deformed slowly by four‐point bending has been investigated over the temperature range 195 to 483 °K. The experimental results are presented in form of Ψ(χ)‐curves. The measured Ψ (χ)‐curves were compared with the curves calculated by Vítek using the theory of thermally activated motion of screw dislocations extended on {110} and {112} planes and good agreement was found above room temperature. Discrepancies between the calculated and measured Ψ(χ)‐curves exist at low temperatures, where slip along {110}‐planes becomes significant. Differences between the Ψ(χ)‐curves measured on the tension and the compression side cannot be satisfactorily explained by existing theories.
The Mean Free Path of Relativistic Electrons for Plasmon Excitation
Authors: Ashley J. C. , Ritchie R. H. 
Published: July 2007

AbstractThe interaction of a relativistic electron with a system of plasmons is considered. First‐order perturbation theory is used to calculate the rate of excitation of plasmons by the incident electron; the excitation rate leads to a mean free path. It is shown that relativistic corrections to the mean free path are generally quite negligible and thus the mean free path calculated using a nonrelativistic incident electron, when expressed in the “proper fashion”, is also correct relativistically.
Energy and Momentum Loss Rates for Hot Electrons in Silicon
Authors: Ahmad S. , Daga O. P. , Khokle W. S. 
Published: July 2007

AbstractUsing of time‐dependent perturbation and deformation potential theories for electronphonon interaction, the rate of change of crystal momentum and energy of electron along the field direction has been estimated in silicon. It is found that the loss rate of crystal momentum of the electron along field direction, due to acoustic phonon collisions is greater than that due to optical phonon collisions, whereas the rate of loss of energy of electrons due to optical phonon interactions is greater than that due to acoustic phonon collisions. The dominant acoustic phonon contribution to the loss rate of the crystal momentum of the electron along field direction is confirmed by the observed and estimated temperature dependence of the drift velocity of electrons in silicon for high electric fields.
Specific Heat and Superconductivity of Binary Alloys Containing V, Nb, and Ta
Authors: Corsan J. M. , Cook A. J. 
Published: July 2007

AbstractThe electronic specific heat coefficient, γ, the Debye temperature, θD, and the superconducting transition temperature, Tc, have been measured for binary b.c.c. alloys of V, Nb, and Ta. These results have been used to investigate the effects of compositional changes on parameters used in the theory of superconductivity to describe the transition temperature. It has been shown that changes in transition temperature with changes in composition cannot be explained simply on the basis of an alteration of the density of states except in the case of binary Nb‐Ta alloys. It is concluded that, for V‐Nb and V‐Ta alloys, changes in the interaction responsible for superconductivity also govern changes in the transition temperature.
Correlations of Electron Spin Resonance Parameters with Fe3+ Sites in Topaz
Authors: Howling D. H. 
Published: July 2007

AbstractCorrelations proposed between crystal field axes obtained from electron spin resonance measurements and specific Fe3+ sites in topaz (Al2[F, OH]2SiO4) have been investigated. The results of three studies have been examined and it is shown that none of the axes‐site correlations proposed is unique. Results obtained for Fe3+ by electron spin resonance are compared with the results of our earlier nuclear resonance studies of Al3+ in topaz. By comparison with the tensor‐site correlations previously advanced for Al3+ sites, preferred correlations between axes and sites for Fe3+ substituting for Al3+ in two groups of sites are given, each group consisting of four equivalent and congruent Al3+ sites.
Subdivision of the B.C.C. Transition Metals
Authors: Chen C. W. 
Published: July 2007

AbstractB.c.c. transition metals are shown to display large, systematic changes in many basic physical properties on going from vanadium to chromium or iron, from niobium to molybdenum, and from tantalum to tungsten. These property changes are attributed, at least partially, to the differences in the electronic structure and nuclear composition between the group V (V, Nb, and Ta) and group VI metals (Cr, Mo, and W) and iron. A subdivision of the b.c.c. transition metals is this proposed. Conditions under which the metals may sensibly be considered as an undivided group are discussed.
Initial Hardening in Quenched Gold
Authors: Bapna M. S. , Mori T. , Meshii M. 
Published: July 2007

AbstractThe effects of dispersed vacancies on mechanical properties were examined in as‐quenched gold single crystals. A quench from 1000 °C produced an initial hardening of ≈200 p/mm2 at 4.2 °K. This hardening increased with the quenching temperature and could be approximated by a linear or square root dependence on the vacancy concentration. The extent of the easy glide region was found to increase without a significant change in the work‐hardening coefficient. No yield drop was generated by the quench. The quenching effects were found to decrease with the test temperature below − 70 °C. The experimental results were interpreted in terms of hardening due to dispersed vacancies and/or small vacancy clusters. The kinetics of the aging at room temperature were also followed by yield stress measurements at liquid helium temperature.
Mössbauer Study of Dy161 in Gd2O3
Authors: Mørup S. , Trumpy G. 
Published: July 2007

AbstractMössbauer studies have been performed with a source consisting of Tb161 in Gd2O3 and with ferromagnetic metallic dysprosium as an absorber. – Hyperfine splitting of the Dy161, produced by the decay of Tb161 in the source has been obtained. The results are interpreted in terms of a pure quadrupole splitting of e2 q Q = 485 MHz at room temperature.
Compton profile anisotropies of Na2S and CaF2 in the LCAO approximation
Authors: Perkkiö S. 
Published: July 2007

AbstractThree directional and the isotropic Compton profiles of the isoelectronic fluorite structure compounds Na2S and CaF2 are calculated using the linear combination of atomic orbitals (LCAO) approximation. The anisotropies between the directional Compton profiles are found to be confined below 2.0 at. units of momentum in the case of Na2S and below 3.0 at. units of momentum in the case of CaF2. The basic features of the anisotropies are found to be the same except near the zero momentum. Fourier transforms of the Compton profiles serve as a check of the reliability of the calculations. They reveal that orthogonalization up to the 21st order of neighbour atoms is sufficient for the [100] and [110] crystal directions but in the [111] crystal direction there are discrepancies for both compounds.
A theoretical study of the thermodynamic properties of diluted and random‐bond ising systems
Authors: Agudelo A. C. , Ospina O. E. , Zamora Ligia E. , Bohórquez A. , Alcázar G. A. Pérez 
Published: July 2007

AbstractThe thermodynamic properties of a diluted and random‐bond Ising model are calculated using the variational method based on the Bogolyubov's inequality for the ferro‐ and antiferromagnetic regions. It is assumed that the system is composed of clusters of one and two spins. Previously reported results for Ising models pure and diluted by site and by bond are recovered with this model.
Fluctuations and susceptibility dispersion in ferroelectrics on the basis of the fokker‐planck equation
Authors: Kaupužs J. 
Published: July 2007

AbstractThe Fokker‐Planck equation is used to calculate the dielectric susceptibility dispersion in ferroelectrics within the Landau‐Ginzburg model. Equations for both the time‐space correlation function and the susceptibility are obtained on the basis of subsequent consideration of fluctuations. Two cases are considered: 1. a small‐size single domain ferroelectric and 2. an infinite‐size ferroelectric. Effects related to a switching of the system between two stable states due to fluctuations are investigated. The obtained results explain in general (without specific effects) both frequency and temperature dependence of the susceptibility (or permittivity) and the dielectric loss angle observed experimentally in ceramics and polycrystals (case 1) as well as in single ferroelectric crystals (case 2).
The Influence of Ultrasound on the Rayleigh Scattering of Mössbauer Radiation in Deformed Crystals. New Integral of Motion of the Takagi Equations
Authors: Iolin E. M. , Muromtsev A. V. , Rusevich L. L. 
Published: July 2007

AbstractThe exact integral of motion Q is found for the Takagi equations. These are transformed from the system of two differential equations with partial derivatives to the system of two ordinary differential equations. The RSMR spectra are analyzed for the cases of perfect and deformed single crystals excited by ultrasound. An oscillatory Q‐dependence of the total intensity of diffracted beam and RSMR spectrum is found.
Spin Wave Theory of Anisotropie Two‐Sublattice Heisenberg Ferrimagnets
Authors: Xue Desheng , Gao Meizhen , Kong Yong , Li Fashen 
Published: July 2007

AbstractIn random‐phase approximation, the method of matrix Green functions is applied to investigate the spin wave spectra and mean values of the spin vector in the z‐direction of anisotropic two‐sublattice Heisenberg ferrimagnets both for NaCl and CsCl structures. The results show that each of the spin wave spectra breaks into acoustic and optical branches and changes closely with the structure type, temperature, and the anisotropic exchange interaction coefficient A. The ground state at T = 0 K has all negative energy states filled by magnons. The thermal expectation values, 〈Sz〉, of the spin in z‐direction are calculated numerically for each sublattice at T = 0 K. It is seen that 〈SZ〉 with A > 1 is larger than that without anisotropy. In the special case of an isotropic antiferromagnet, our results agree completely with the existing works.
ESR Study of the Phase Transition Sequence in Betaine Phosphite
Authors: Pöppl A. , Völkel G. , Metz H. , Klöpperpieper A. 
Published: July 2007

AbstractThe structure of the PO radical is examined by ESR spectroscopy in γ‐irradiated betaine phosphite. The ESR spectra of the PO radical indicate two phase transitions of betaine phosphite at Tc1 = 355 K and Tc2 = 216 K. The symmetry of the ESR spectra of the PO center in the paraelastic, antiferrodistortive, and ferroelectric phases of betaine phosphite is in accordance with the space groups P21/m, P21/c, and P21.
On the Conditions of the Magneto‐Optical Kerr Effect Enhancement in Metallic Bilayers
Authors: Zhou Shi‐Ming , Zhai Hong‐Ru , Lu Mu , Miao Yong‐Zhi , Song Jing‐Tao , Zhang Hong‐Yan 
Published: July 2007

AbstractThe magneto‐optical Kerr rotation spectra of Fe/Ag, Fe/Au, and Ni/Cu bilayers are measured and calculated based on Fresnel's equations. The theoretical spectra agree with the measured ones. A magneto‐optical Kerr effect enhancement peak is observed near 600 and 500 nm for the bilayers Fe/Ag and Fe/Au, respectively, with the Fe layer thickness less than the light penetration depth. No Kerr effect enhancement occurs for Ni/Cu bilayers for any thickness of the Ni layer. It is concluded that the plasma or the absorption edge of the reflector in bilayers is neither a necessary nor a satisfactory condition but provides an important opportunity for the enhancement. Whether the enhancement occurs depends not only on the optical constants of the reflector but also on the optical and magneto‐optical parameters of the top ferromagnetic layer.
Electron Energy Structure of Boron Nitride and Diamond. Similarities and Distinctions
Authors: Ilyasov V. V. , Nikiforov I. Ya. , Safontseva N. Yu. 
Published: July 2007

AbstractWith the coherent potential method of the multiple scattering theory the electronic structure of boron nitride (in sphalerite modification) and diamond is calculated. The cluster approximation with muffin‐tin crystal potential is used. The electron structure and chemical bonding of these substances are investigated for the first time with this modern theoretical method. It is shown that the chemical bonding has mainly covalent character, the ionicity being about 20%. A fine structure of the upper part of the valence band of boron nitride is revealed and its nature is discussed. The similarity of the total electron state densities of the diamond and boron nitride in sphalerite modification is proved and the distinctions are discussed. The calculated local partial electron densities of states are used to explain the experimental X‐ray emission and X‐ray photoemission spectra of diamond and boron nitride.
NMR Investigations of Molecular Motions and Critical Dynamics at the Ferroelectric Phase Transition of Tris‐Sarcosine Calcium Chloride
Authors: Michel D. , Hacker U. , Erge Th. , Petersson J. 
Published: July 2007

Abstract35Cl and81Br quadrupolar perturbed NMR measurements in single crystals of tris‐sarcosine calcium bromide (TSCB) and tris‐sarcosine calcium chloride (TSCC) are used to study molecular motions and the dynamical critical behaviour near the ferroelectric phase transition of TSCC. At temperatures higher than about 130 K the spin‐lattice relaxation timeT1of81Br nuclei in TSCB is dominated by an activated process with an activation energy of 28 kJ/mol which is attributed to the reorientation of parts of the sarcosine molecule. The results are compared with those obtained from35Cl measurements of TSCC. Near the ferroelectric phase transition of TSCC at 131.5 K a critical contribution to the35Cl spin‐lattice relaxation rate is observed which can be explained on the basis of the standard mean‐field model in accordance with the static critical behaviour belowTc.
Pressure Dependence of Co Diffusion in Amorphous Fe40Ni40B20
Authors: Rummel G. , Mehrer H. 
Published: July 2007

AbstractThe pressure dependence of the diffusion coefficients of Co is studied in structurally relaxed meltspun amorphous Fe40Ni40B20. The non‐crystallinity of diffusion samples before and after the high‐pressure diffusion anneals is checked by X‐ray diffractometry. The radiotracer 60Co is used and ion beam sputtering is employed for serial sectioning of diffusion samples. The activation volume for diffusion is Δ V = −(0.07 ± 0.02) atomic volumes of Co. Within the experimental errors no significant pressure dependence is observed. This observation indicates that Co diffusion in Fe40Ni40B20 is likely to be mediated by a collective mechanism.
The Crystalline Structure as a Basis for a Reversed Access to the Special Theory of Relativity
Authors: Günther H. 
Published: July 2007

AbstractLorentz symmetries in solids become evident if the soliton properties of kinks on dislocations for the measurement of length and time are used. This procedure can be extended for deriving the complete theory of special relativity, thus reversing the traditional way. The continuum approximation of the crystalline lattice with dislocations appears as a model for a relativistic space‐time.
Mechanical Behaviour of Linear Viscoelastic Liquids
Authors: Povolo F. , Hermida Élida B. 
Published: July 2007

AbstractThe mechanical properties of some amorphous materials can be described in terms of a modified anelastic element (MAE). The characteristics of this element, developed in a previous publication, are extended in order to describe the mechanical behaviour of linear viscoelastic liquids. This treatment leads to the modified standard linear liquid (MSLL). Through this phenomenological model the quasi‐static and dynamic moduli or compliances of viscoelastic liquids can be analytically expressed as a function of time or frequency. The parameters involved in the equations – γ, t0 or ω0, and η0 – are related to the width and the mean characteristic time of the relaxation or retardation spectrum and to the zero‐shear‐rate viscosity of the specimen. A procedure to determine the parameters of the MSLL from dynamical properties is proposed. It is applied to measurements in molten polypropylene (PP) given in the literature, and the results are discussed. Moreover, since the shape of the spectrum associated to the MSLL is quite similar to the well‐known log‐normal distribution function, also a comparison is done.
On the Hartree Interaction in Quasi‐2D Systems
Authors: Combescot Monique 
Published: July 2007

AbstractThe Hartree interaction in quasi‐2D systems (i.e. the Coulomb excitations with zero momentum transfer) is rederived without introducing any particular cut‐off to withdraw the divergences arising from the long‐range character of the Coulomb potential. It is shown that the remaining finite part is indeed independent of the cut‐off as physically expected.
Tight‐Binding Approach for the Band Structure of GaAs‐Type Semiconductors
Authors: Merian M. , Lampel G. , Coqblin B. 
Published: July 2007

AbstractThe band structure of GaAs‐type semiconductors is studied within a tight‐binding calculation, taking into account the s and p atomic energies including spin‐orbit couplings for both anions and cations. The 16 × 16 matrix is solved analytically in perturbation theory for the conduction band near the Γ‐point, which yields an analytical derivation of the k3‐term. The computed values of the coefficient of the k3‐term agree with experimental ones in III–V semiconductors.
Atomic Short‐Range Order in Cu17 at% Mn
Authors: Roelofs H. , Schönfeld B. , Kostorz G. , Büher W. 
Published: July 2007

AbstractThe elastic diffuse neutron scattering from a Cu–17.2 at% Mn single crystal aged at 483 K to produce an equilibrium state of atomic short‐range order is measured at room temperature in a minimum separation volume of reciprocal space. Warren‐Cowley short‐range order parameters and coefficients of linear static displacement scattering are determined by least‐squares fitting. Effective pair potentials obtained from the short‐range order parameters by applying the inverse Monte‐Carlo method are used to calculate the diffuse antiphase boundary energy γAPB. For copper‐base alloys the concentration dependence of γAPB is one of the suggested reasons for the transition of wavy to planar slip. Based on the values of γAPB, the concentration ranges for the transition in CuMn, CuAl, and CuZn may be understood.