bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Transformations in the Mn2GeySb1−y System in Strong Magnetic Fields under High Pressure
Authors: Galkin A. A. , Zavadskii E. A. , Morozov E. M. 
Published: July 2007

AbstractAt temperature changes some magnetic phase transformations are observed in the Mn2Gey Sb1−y system, which are accompanied by magnetic structure changes. The main characteristics of such transformations, magnetization change, change of the entropy of the spin system, and transition heat, were determined on the basis of magnetic measurements over a wide range of magnetic fields. The effect of pressure on the magnetic transformation temperature was also studied. An analysis of the experimental results is made on the basis of Kittel's exchange inversion theory.
Self‐Diffusion in Selenium
Authors: Brätter P. , Gobrecht H. 
Published: July 2007

AbstractSelf‐diffusion measurements have been carried out in single crystals of the semiconductor element selenium using a residual activity method and Se‐75 as the tracer in the temperature range 152 to 215 °C. In the direction of the trigonal axis (| c‐axis) the data of the lattice diffusion can be represented by D⟂ = 0.2 exp (—1.2 eV/kT) cm2 s−1. The diffusion along the short circuit paths can be approximately described by the values Q≈︁ 0.5 eV and Q≈︁ 0.7 eV for the activation energy and by diffusion coefficients between 5 × 10−10 and 10−8 cm2 s−1 in the temperature range considered. The vacancy formation enthalpy in selenium is estimated to be about 0.75 eV. From the diffusion data determined the vacancy migration enthalpy is estimated to be about 0.5 eV along the c‐axis and 0.7 eV perpendicular to the c‐axis. It is possible to explain the self‐diffusion in selenium on the basis of a vacancy mechanism. The anomalous self‐diffusion behaviour of the elemental semiconductors and correlation considerations are discussed. Several typical features were found and the presented results for selenium are shown to be in agreement.
Asphericity of the 3d Magnetic Moment Distribution and Conduction Electron Polarization in Co–Fe Alloys
Authors: Dobrzyński L. , Maniawski F. , Modrzejewski A. , Sikorska D. 
Published: July 2007

AbstractInvestigations of magnetic form factors of Co–Fe (f.c.c.) alloys by polarized neutrons are described. It is shown that the asphericity of the spin‐density distribution and the magnetic moment of conduction electrons increases with the iron content. Both results are discussed in terms of the existing theories of magnetism in transition metals. The results obtained for the most heavily doped sample, Co0.86F0.14, indicate on the existence of the iron‐iron interaction which probably leads to a change of the electronic structure of iron.
Crystal Vibrations of Silicon by the Use of Valence Force Potentials
Authors: Singh B. D. , Dayal B. 
Published: July 2007

AbstractThe dispersion curves for silicon in the symmetry directions [ζ, 0, 0], [ζ, ζ, 0] and [ζ, ζ, ζ] are calculated using valence force potentials. Two different models have been used, the one with three valence force constants and the other with six valence force constants. The initial set of three valence force constants have been derived by incorporating Lippincott potential in the general valence force field for silicon. The force constants have been refined using a manual method and further by a least square fitting program with some known neutron scattering frequencies. The results with the six adjusted valence force constants potential model are in good agreement with the experimental results. The Debye characteristic temperatures have been calculated and they are in good agreement with the experimental values.
Upper Critical Field Changes in Electron‐Irradiated Niobium
Authors: Ullmaier H. , Papastaikoudis C. , Schilling W. 
Published: July 2007

AbstractMeasurements are reported of the dependence of the upper critical field Hc 2 on the concentration and configuration of Frenkel defects in niobium. The defects were produced by low‐temperature irradiation with 3 MeV electrons and subsequent annealing treatments. The results qualitatively confirm a theory by Eilenberger which predicts that Hc 2 not only depends on the electronic mean free path but also on the ratio between s‐ and p‐wave scattering of the defects.
High Electric Field Effects and Electron Transfer to Higher Conduction Band Minima in Gallium Antimonide
Authors: Heinrich H. , Jantsch W. 
Published: July 2007

AbstractThe current–voltage characteristic of n‐type GaSb has been measured up to 9 kV/cm at 300 °K, and results for the longitudinal magnetoresistance at 300 °K are given up to 7 kV/cm. The experiments are compared with calculations based on a two‐band model taking into account carrier transfer to higher valleys. Avalanche breakdown is observed at the highest field strength under investigation.
Die magnetische Anisotropie plastisch verformter Nickel‐Einkristalle
Authors: Gessinger H. 
Published: July 2007

AbstractMit Hilfe eines dynamischen Magnetometers wurde die Anisotropie des Einmündungsgesetzes sowie der Remanenz an plastisch verformten Nickel‐Einkristallscheiben gemessen. Für quantitative Aussagen am geeignetsten erwiesen sich im Einmündungsgebiet die Messungen an Proben mit der Scheibenorientierung (111), da hier die Ergebnisse in einfacher Weise der Kristallanisotropie, der Verformungsanisotropie und der Formanisotropie zugeordnet werden können, während sich bei anderen Scheibenorientierungen die Fourier‐Koeffizienten in komplizierter Weise aus den verschiedenen Anisotropiebeiträgen aufbauen. Messungen der Temperaturabhängigkeit lieferten eine experimentelle Bestätigung der aus theoretischen Überlegungen gefolgerten Zuordnung dieser Koeffizienten.
Electrostatic Field in a Slightly Orthorhombic Ionic Crystal — Application to the Calculation of Tetragonal BaTiO3 and PbTiO3 Birefringence
Authors: Bouillot J. , Machet R. , Tsallis C. 
Published: July 2007

AbstractThe electrostatic dipole field coefficients are calculated for every point near a symmetry point of a simple cubic lattice with slight orthorhombic deformation. The internal dipole field is developed to the 2nd order as a function of the deformation and the displacements from the symmetry points. As an application the birefringence of tetragonal BaTiO3 and PbTiO3 is calculated and it is found that the contribution of ionic displacements is not negligible.
Higher‐Order Elastic Constants of the Inert Gas Solids
Authors: Mock W. , Rose M. F. 
Published: July 2007

AbstractThe second‐, third‐, and fourth‐order elastic constants at T = 0 °K have been calculated using the Mie‐Lennard‐Jones 12‐6 potential, the Buckingham 14‐6 potential, and the Morse potential. The zero‐point contribution to the second‐ and third‐order constants was taken into account using the quasiharmonic approximation by obtaining the second and fourth moments of the harmonic frequency distribution. The pressure dependence of the second‐order constants has been evaluated and thus the pressure dependent bulk modulus. From the bulk modulus 0 °K isotherms for Ne have been calculated and compared with experiment.
Effect of Pressure on the Curie Point of the Pseudo‐NiAs‐Type Cr3Te4
Authors: Ozawa K. , Yanagisawa S. , Yoshimi T. , Ogawa M. , Anzai S. 
Published: July 2007

AbstractMagnetic induction and electrical resistivity of Cr3□Te4 including vacancies of magnetic atoms have been investigated in the vicinity of the Curie temperatures at hydrostatic pressures up to 6 kbar. The magnetic induction smoothly vanishes at the Curie temperature, Tc = 325 °K. The electrical resistivity shows a I'‐type anomaly with a kink at 319 °K and atmospheric pressure, and this temperature is in agreement with the Curie temperature. The pressure effect on the Curie point has been obtained as: (dTc/dP) = ‐(6.2 ± 0.4) deg/ kbar from the magnetic induction, and (dTc/dP) = ‐(5.9 ± 0.3) deg/kbar from the electrical resistivity measurements. Although a large number of exchange chains are cut by the vacancies in Cr3□Te4, only little difference has been observed in the Curie temperatures between CrTe and Cr3□Te4. This is not explained by a volume effect of exchange integral on the Curie temperature with dTc/dP < 0 in Cr3□Te4, and a brief discussion of exchange interactions in this compound has been done in comparison with those in CrTe on the basis of the ionic model.
A Structural Model for Grain Boundaries in Pure Metals
Authors: Baroux B. , Biscondi M. , Goux C. 
Published: July 2007

AbstractThe transition lattice between two crystals of different orientations in a metallic bicrystal is computed on the basis of simple geometric assumptions. The individual displacement of each atom can be described for any type of boundary. The resulting structure obviously coincides with the dislocation array for low misorientations. From this model, a part of the grain boundary's energy can be calculated with a non‐central force assumption; the results for tilt boundaries around 〈001〉 in aluminium show a strong dependence on misorientation.
Stationary State of Non‐Equilibrium Plasmas in Semiconductors with Finite Cross‐Section
Authors: Holter Ø. , Johnson R. R. 
Published: July 2007

AbstractNon‐equilibrium plasmas created by impact ionization in semiconductors are investigated. With constant axial current densities it is shown that the plasma is homogeneous in the axial direction. Expression for the radial density profiles are given in the limit of low and high plasma density. The numerical solution yields the impact ionization coefficient as a function of the total density. This relation is interpreted as a qualitative current‐voltage characteristic. With material specifications appropriate for InSb a region of negative differential conductivity is found for p‐InSb, but not for n‐InSb. The location of the turning point, corresponding to an infinite differential conductivity, is compared with Ancker‐Johnson's experimental results in p‐InSb.
Relative Resistivity Anisotropy in Ferromagnetic 3d Metals and Alloys
Authors: Vasilyev Yu. V. 
Published: July 2007

AbstractUsing experimental results of the author's investigations, a possible model is proposed which explains the behaviour of the relative resistivity anisotropy in ferromagnetic 3d metals and alloys in a planar magnetic field of 4 kOe. The local magnetic moment disturbances scattering mobile d‐electrons within the frame of a “cocktail” model of ferromagnetism are assumed to be responsible for the anisotropy of the resistivity, s‐electrons being considered as isotropic and giving the main contribution to the total electric conductivity.
Enhancement of Thickness Fringe Contrast in Thick Crystals at Low Accelerating Voltages
Authors: Sheinin S. S. 
Published: July 2007

AbstractThe contrast of thickness fringes in thick crystals has been studied for various diffraction conditions. The results show that, under certain circumstances, it is possible to obtain fringes in considerably thicker crystals than is normally possible. These fringes arise from the interference of two well transmitted Bloch waves as opposed to the familiar thickness fringes which result from the interference of one Bloch wave which is well transmitted and the other which is highly absorbed. The effects of absorption under these circumstances are similar to those obtained when normal absorption only is present.
Dislocation Motion in Secondary Slip Planes in Alkali Halide Crystals at Room Temperature
Authors: Yu. Gutmanas E. , Nadgornyi E. M. 
Published: July 2007

AbstractDislocation motion in {100} 〈110〉 and {111} 〈110〉 secondary slip systems has been observed in NaCl, KCl, KBr, KI, and RbI crystals at room temperature by means of a special loading and etch‐pit technique. The observed reduction in the difference between the critical resolved shear stress τs{110} in the primary slip system {110} 〈110〉 and τs in the secondary slip system in the above sequence of crystals demonstrates the increasing influence of multiplication processes of dislocations on dislocation motion in the primary system. A considerably lower effect of γ‐irradiation on τs{100} and τs{111} has been found in comparison with that of τs{110}. Possible reasons are discussed briefly.
Optical and Magnetooptical Studies of the Interband Transition of Holes in Tellurium
Authors: Hardy D. , Rigaux C. 
Published: July 2007

AbstractThe interband transitions of holes in tellurium by absorption experiments are investigated in the energy range 100 to 170 meV on variously doped single crystals (1014 to 5 × 1017 holes/cm3) between 1.6 and 77 °K. Calculations of the absorption spectrum due to the direct inter‐valence band transitions are performed, using for the two split valence bands the dispersion relation . Theoretical curves account quantitatively for the experimental absorption data obtained at 23 and 77 °K. The comparison of the computed and observed spectra enables us to determine the parameters of the theoretical model. The existence of transitions into an impurity level appears at very low temperature. Results of magnetoabsorption experiments obtained at low field are reported.
On the Critical Point Behaviour of a Model of a 3‐d Ising Ferromagnet
Authors: Gupta A. K. 
Published: July 2007

AbstractAn analysis is made of the critical‐point behaviour of a 3‐d Ising ferromagnet using a magnetic equation of state based on an expression for the order‐parameter proposed by Frankel. The asymptotic distribution‐function of zeroes for the partition function on a unit‐circle in a complex‐fugacity plane is determined. The critical indices γ and α are found to be 1, and 0 which are inconsistent with high‐temperature series expansion results.
Peculiarities in the Vibrational Spectra of Cesium and Rubidium Nitrate Crystals in Its Low‐Temperature Phases
Authors: Karpov S. V. , Shultin A. A. 
Published: July 2007

AbstractPolarized ir absorption spectra of CsNO3‐II and RbNO3‐IV crystals have been investigated in the region of the fundamental vibrations of the nitrate ions at 80 and 300 °K as well as the Raman spectra of these crystals at room temperature. Apart from the local field effects and the Davydov splitting of some vibrational terms also a splitting due to the presence of several sets of molecules not related by symmetry in a unit cell was observed. These results agree with the more accurate data of X‐ray analysis of the crystal structure of the low‐temperature phases of cesium and rubidium nitrate.
X‐Ray Spectra, Energy Band Structure, and Superconductivity of V3X‐Type Compounds
Authors: Nemnonov S. A. , Kurmaev E. Z. , Belash V. P. 
Published: July 2007

AbstractX‐ray K‐emission bands of the metal atoms from Me3X‐compounds (V3Ga, V3Si, V3Ge, Cr3Si) are investigated. A multiple‐band structure of the energy spectrum is found characterized by a number of overlapping bands related to non‐metallic s‐, p‐, and metallic dp‐states. The results of theoretical calculations for V3Ga, V3Si, and V3Ge (Mattheiss [9]) are found to correlate well with experimental data. Some deviations, especially in the lower part of valence band are attributed to the choice of the crystal potential. On the basis of experimental results it seems possible to suggest theoretical calculations using a crystal potential corresponding to the 3d34s2 vanadium atom configuration. The relationship between the electronic structure of Me3X‐compounds and the change of their superconducting properties is discussed.
Ultrasonic Attenuation in Current‐Carrying Superconductors Containing Paramagnetic Impurities
Authors: Kolpagiu M. K. , Kon L. Z. 
Published: July 2007

AbstractAn investigation is made of the ultrasonic attenuation in superconductors carrying persistent currents in the presence of paramagnetic impurity scattering. The limiting case of high impurity concentrations is considered. General expressions for the attenuation coefficients are obtained in the case of space independent sound waves. The attenuation coefficients at relatively low‐frequencies and low temperatures are evaluated explicitly. Gapless superconductors are also considered.
Possibility of the Excitonic Phase in Insulators
Authors: Zimmermann R. 
Published: July 2007

AbstractApplying many‐particle methods the lowest excitation energy of the exciton is calculated for an insulator with small energy gap. Screening is taken into account by means of a self‐consistent k‐dependent screening function. At the finite critical gap Gc the excitation energy vanishes leading to the excitonic phase.
Non‐Linear Dipole Effects in the Infra‐Red Absorption of GaAs
Authors: Borik H. 
Published: July 2007

AbstractThe IR absorption spectrum of GaAs is calculated and a good agreement with the measured bands is achieved. A considerable part of the two phonon bands is due to second order dipole moment absorption. The simplest kind of a model for cubic anharmonicity and the second order dipole moment has proved to work satisfactorily. The constant ratio between dipole and anharmonic coupling coefficients characteristic for this type of interaction is represented in terms of optical constants and the static ionic charge. The difference between an effective value for this ratio taken from the IR data and the one valid for the short range type of coupling coefficients is of reasonable magnitude.
Neutron Diffraction Study of Nickel in the Liquid State
Authors: Waseda Y. , Suzuki K. , Tamaki S. , Takeuchi S. 
Published: July 2007

AbstractThe structure of nickel in the liquid state has been studied by neutron diffraction at 1500 °C. After calculating the interference function (Fourier analysis), the atomic radial distribution function was evaluated from which interatomic distance and coordination number were obtained.
Explicit Expressions for Dislocation Derivatives
Authors: Malén K. , Lothe J. 
Published: July 2007

AbstractDerivatives of straight dislocation data are developed using standard perturbation theory and a six‐dimensional formulation of the eigenvalue problem. The angular derivatives can be used for the calculation of the elastic field from a curved dislocation loop. The velocity derivatives for uniformly moving dislocations are known to be related to such quantities as kinetic energy or mass.
Model Calculations for Electrons in Amorphous Structures with Short‐Range Order
Authors: Maschke K. , Thomas P. 
Published: July 2007

AbstractThe distribution of poles of the averaged one‐electron Green's function in the complex k‐space has been investigated for a simple model consisting of point scatterers which form a slightly distorted primitive cubic lattice without long‐range order. For energies within the energy band of the corresponding crystal the poles of the amorphous case are found to represent “quasi‐crystal electrons” which, for small disorder, may be classified in a sense by a k‐vector, while for energies near the crystal band edges (inside or outside the crystal band) the states are no longer comparable with crystalline states.
Exchange Interaction between Excitons in the Quasi‐Cubic Model
Authors: Skettrup T. , Balslev I. 
Published: July 2007

AbstractThe general properties of the exchange matrix element between hydrogenic exciton states in a cubic crystal are discussed. It is shown that the high frequency dielectric constant should be applied in the screening of the long range exchange interaction. The exchange effects are then incorporated in the quasi‐cubic model of uniaxial crystals. Including also an external stress the energy levels and oscillator strengths of the exciton states are derived. The theoretical results are consistent with existing optical data on ZnO. By comparison values for the exchange integral and a valence band deformation potential are obtained.
An Effective Field Model of the Amorphous Antiferromagnet
Authors: Simpson A. W. 
Published: July 2007

AbstractAn effective field model of an amorphous antiferromagnet is developed assuming a distribution of near neighbour distances and hence a distribution of effective field coefficients between interacting atom pairs. It is shown that such a material is characterized by a symmetrical distribution of the total effective field, which, in the absence of any spin correlation, is approximately Gaussian. The model predicts a precise critical or Néel temperature proportional to the square root of the average number of interacting near neighbours, and an unusual downward curvature of the reciprocal susceptibility variation with decreasing temperature (see Fig. 5 and 6). Two classes of amorphous antiferromagnet are examined: those with and those without magnetically isolated paramagnetic atoms. The limited experimental data support the former class.
Fine Structure of Weak Kinematical Diffraction Beams for a Foil Containing Domain Boundaries
Authors: de Ridder R. , van Landuyt J. , Gevers R. , Amelinckx S. 
Published: July 2007

AbstractR. DE RidderA kinematical scattered beam emerging from a foil containing a coherent domain boundary shows a fine structure which is analysed on the basis of the two‐beam kinematical theory [7]. First, the wave function of a kinematical beam at the exit surface is deduced and a physical interpretation is given. The fine structure of the beam is derived by applying the Fourier‐transformation method outlined in previous papers [1 to 4]. The geometry of the fine structure is analysed and the intensity behaviour of the satellites discussed taking anomalous absorption into account. Finally, the relation between the constituent beams and the fringe pattern is emphasized and the origin of the several satellites is demonstrated by a dispersion surface construction.
Electromultipole Interaction and Paramagnetic Relaxation in Ruby II. Shielding of the Ion Multipoles in the Crystal Lattice
Authors: Peskovatskii S. A. 
Published: July 2007

AbstractSpecial features of the crystal lattice shielding of electric fields nonuniform at interatomic distances are discussed. It is found that in this case electric field gradients may exceed those in homogeneous dielectrics (antishielding effect). The dependence of the magnitude of the effect on the lattice parameters is analysed. Estimates of antishielding factors for dipole and quadrupole moments in ruby were made.
Optical Absorption of Ferroelectrical Iron Boracites
Authors: Pisarev R. V. , Druzhinin V. V. , Nesterova N. N. , Prochorova S. D. , Andreeva G. T. 
Published: July 2007

AbstractThe optical absorption in iron boracites Me3B7O13X, where Me = Fe2+ and × = Cl, Br, I, and also in cubic RbFeFe3 has been studied in the spectral range 0.25 to 25 μm from 77 to 650 °K. Boracite spectra are characterized by one intense band identified with the 5T2g → 5Eg electronic transition and by a large number of less intense bands in the visible and ultraviolet range of the spectrum. In RbFeF3 the splitting of the 5Eg state is connected with the Jahn‐Teller effect. Such splitting is not observed in iron boracites. Theoretical and experimental investigations of the intensity of the electronic transitions are performed. They showed that the main contribution to the intensity of transitions can be given by an electron‐vibrational and ferroelectric dipole mechanism. In boracites at the phase transition temperatures (trigonal – orthorhombic – cubic) an abrupt change of the position and intensity of the bands was observed.
Optical Absorption of Self‐Trapped Holes in AgCl and AgBr
Authors: Ulrici W. 
Published: July 2007

AbstractIn AgCl crystals doped with V3+, Cr3+, Fe3+, Ni2+, Cu2+, and chalcogen an infrared absorption at 9200 cm−1 is measured after irradiation at 20 °K. By comparison with ESR measurements on these crystals the infrared absorption can be assigned to holes trapped at lattice cations (Ag2+). The localization of the holes at lattice cations is explained by the valence band structure of silver halides and a Jahn‐Teller effect of the 4d9 configuration. AgBr crystals doped with V3+ or Cr3+ show after irradiation at 20 °K an infrared absorption at 7100 cm−1 with analogous properties as in AgCl.