bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mixing of 3d and Excited Orbitals of an Iron Group Ion in a Tetrahedral Field and Its Effect on Orbital Momentum and Spin‐Orbit Coupling Coefficient
Authors: Basu C. , Majumdar D. , Ghosh U. S. 
Published: July 2007

AbstractMixing of 3d and excited orbitals such as 4p, 4d, and 4f of an ion via crystal field and the effect of this mixing on the orbital moment and the spin‐orbit coupling coefficient have been discussed for the case of iron‐group complexes of tetrahedral coordination. It has been shown that the admixture of excited orbitals to the 3d orbitals effectively reduces the orbital moment and S—O coefficient with respect to the values corresponding to pure 3d orbitals. These reductions have been estimated for different ions of tetrahedral coordination within the framework of crystal field theory. The reduction of the S—O coefficient is found to be larger than that of the orbital moment. It has been inferred that in some of the ions the reductions due to the admixture of excited metal orbitals may not be negligible when compared with those produced by the covalency effect although the latter, in general, causes a larger reduction of the two parameters.
Anisotropy of Cyclotron and Spin Mass of n‐ and p‐Type PbSe
Authors: Kästner P. 
Published: July 2007

AbstractThe variation of the spin splitting of Landau levels as a function of the angle between magnetic field and crystallographic axes of n‐ and p‐type lead selenide was investigated by observing magnetoacoustic quantum oscillations at 1.5 K. The main result is that within experimental error the spin mass shows the same anisotropy as the cyclotron mass. The ratio K of longitudinal to transverse mass presented in this paper is 1.70 for n‐ and 1.87 for p‐PbSe in good agreement with values reported by other authors.
High‐Frequency Conductivity of Hot Carriers in Semiconductors with Non‐Parabolic Dispersion Law in the Presence of a Magnetic Field
Authors: Almasov L. A. 
Published: July 2007

AbstractThe conductivity of semiconductors with respect to a weak alternating electric field in the presence of applied stationary electric and magnetic fields has been calculated. The energy band of free carriers is supposed to be isotropic but, in general case, non‐parabolic. Different special and limiting cases are considered. It is shown that the non‐parabolicity of the energy bands leads to qualitatively new results in the infrared range.
Enhancement of the Capture Rate of Excess Carriers Due to Acousto‐Electric Amplification
Authors: Nimtz G. 
Published: July 2007

AbstractThe recombination behaviour of excess carriers was investigated during the process of acousto‐electric amplification. The experiments were carried out with the piezoelectric semiconductor tellurium. A decrease of the lifetime of the excess carriers was observed up to four orders of magnitude depending on the intensity of the amplified acoustic flux. The new recombination effect is explained by about 1018 states/cm3 in the forbidden band. These states are a consequence of the random nature of the carrier potential energy in the acousto‐electrically amplified flux, as was shown by Bonch‐Bruevich quite recently. The high intensity flux gives rise to a density of states in the band gap analogous to disordered semiconductors.
Lattice Dynamics of Cadmium at 88 K
Authors: Toussaint G. , Champier G. 
Published: July 2007

AbstractPhonon‐dispersion curves along the [0110], [1120], and [0001] symmetry directions of the h.c.p. metal cadmium have been measured by diffuse scattering of X‐rays at 88 K. A general interatomic force‐constant model has been used to fit the phonon frequencies and interactions up to at least sixth neighbours have to be taken into account. A frequency‐distribution function has been calculated and used to calculate the specific heat and anisotropic Debye‐Waller factor. Finally, by identifying the calculated frequency dispersion curves to the curves obtained from X‐ray scattering experiments, the parameters of a pseudopotential model are calculated.
Electron Paramagnetic Resonance Spectra of Ti3O5 Crystals
Authors: Schlenker C. , Buder R. , Schlenker M. , Houlihan J. F. , Mulay L. N. 
Published: July 2007

AbstractEPR spectra have been recorded at 77 °K on Ti3O5, crystals which were found to be twinned by X‐ray characterization. The spectra show several weak lines and two intense lines with anisotropic g‐factors. The presence of the two main lines has been attributed to the twinning. The line intensity corresponds to a spin concentration of the order of 10−4 of the Ti3+ ions. The spectra are believed to be due to Ti2+ ions and related to the breaking of some covalent metal‐metal bonds involving the localization of come 3d electrons on one of the three different Ti sites. The line anisotropy has been ascribed to the distorted octahedral crystal field.
Quasi‐Elastic Neutron Scattering on Hydrogen in Niobium Single Crystals
Authors: Stump N. , Gissler W. , Rubin R. 
Published: July 2007

AbstractQuasi‐elastic neutron scattering experiments on the system NbH0.07 have been performed with Niobium single crystals at T = 235 and 256 °C. The width of the quasi‐elastic line has been measured 1) for fixed momentum transfer |x|, changing the angle between x and a reference plane of the crystal, and 2) dependent on |x|, the x‐vector parallel to three symmetry directions. The results have been compared with theoretical half widths corrected for experimental resolution. They favour the tetrahedal site model assuming simple jump diffusion. However, in the (001) direction deviation from the predicted behaviour occurs and the obtained value of the mean residence time differs by a factor of two from that derived from the macroscopic diffusion constant assuming tetrahedral sites.
Allowed and Forbidden Hyperfine Transitions in the Electron Paramagnetic Resonance of Mn2+ Doped in Ferroelectric NaNO2
Authors: Upbeti G. C. 
Published: July 2007

AbstractSome interesting observations have been made on the allowed and forbidden hyperfine transitions in the electron paramagnetic resonance of Mn2+ doped in single crystals of ferroelectric NaNO2. The observed field dependence of the spacings of hyperfine lines in the M = + 1/2 ↔ − 1/2 transition for H∥Z is related to the zero‐field splitting parameter D. An interesting result is the observation of forbidden hyperfine transitions along the Y and Z principal axes of the Mn2+ complex. The observed doublet separations are unusual and highly anisotropic necessitating the inclusion of the anisotropic term I. R. H in the spin‐Hamiltonian. The parameters for the best fit of the forbidden doublets are Q′ = −3.18 G, Q″ = +0.53 G, Rx = + 1.65 × 10−3, Ry = + 1.19 × 10−3 Rz = −0.93 × 10−3.
Monte Carlo Calculations on Electron Transport in CdTe
Authors: Borsari V. , Jacoboni C. 
Published: July 2007

AbstractA theoretical analysis of high‐field electron transport in CdTe has been performed with the Monte Carlo technique for different temperatures and ionized impurity contents. The negative differential mobility is due to the combined effect of the increasing population of the low‐mobility satellite valleys and of the intervalley scattering on the mobility of the electrons in the central valley. Which of the above mechanisms is predominant depends on the particular values of physical parameters which, in the case of CdTe, are not yet well known. Ionized impurity scattering maintains its influence on the electron drift velocity also at very high applied fields, above the threshold value (around 10.5 kV/cm at 77 °K). At these fields the electron mean energy is very high. and one would expect the effect of such scattering to be negligible. This feature must not be attributed to an effect of the ionized impurities on very fast electrons but rather to the larger number of electrons that ionized impurity scattering keeps in the more randomized low energy part of the distribution function. The present theoretical results are discussed and compared with recent experimental data.
Annealing Effects on the Thermoelectric Power and a Model for Low‐Field Conduction in Amorphous Germanium
Authors: Vescan L. , Telnic M. , Popescu C. 
Published: July 2007

AbstractNew measurements of the temperature dependence of conductivity σ and thermopower Q in a‐Ge at different annealing stages are reported and a previous model for the low‐field conduction is developed in order to account for experimental data. The model explains the T1/4 law of the conductivity, σ = σ0exp (– M T−1/4), gives concrete expressions for σ0 and M and accounts for the small negative values of Q in the T1/4 region. An explanation for the annealing effects is sketched.
On the Theory of the Electron States and the Surface Conductivity of a Semiconducting Slab
Authors: Dimitrov H. D. , Grânǎarova E. I. 
Published: July 2007

AbstractThe surface electrical conductivity of a thin semiconductor film with electric dipoles on the surface is calculated. Surface electron states connected with the semiconductor–dielectric interface are investigated and the influence of the image forces on the surface conductivity is evaluated. In some cases these forces give rise to two‐dimensional surface energy bands at a depth of about 0.01 eV in the energy gap, so that they must be taken into consideration.
New Types of Superdislocations in Ordered L10 Structure
Authors: Gbeenberg B. A. 
Published: July 2007

AbstractA new type of glissile superdislocations in an ordered L10 structure is proposed. Such superdislocations can arise from known glissile superdislocations with a (2 a/2) 〈110〉 Burgers vector either as a result of their dissociation, or as a result of their interaction with ordinary dislocations. Sessile dislocation configurations are discussed which arise as a result of definite transformations from superdislocations and are barriers hindering the movement of dislocations. Studies were made of specific configurations of dislocation dipoles and nodes in a given alloy, as well as some peculiarities of interaction of superdislocations with domain boundaries.
Surface Impedance of Type I Superconductors in a Weak Magnetic Field
Authors: Kaner E. A. , Yampolskii V. A. 
Published: July 2007

AbstractThe electromagnetic absorption is investigated theoretically in type I superconductors placed in a weak magnetic field parallel to the surface of the specimen. A shallow potential box has been considered which contains a single magnetic surface level. The energy of the surface state is calculated. At zero temperature the electromagnetic absorption threshold decreases. At temperatures of the order of the energy gap the surface impedance possesses a logarithmic singularity at the frequency corresponding to the excitation transition from the magnetic surface level into continuum. The temperature dependence of the electromagnetic absorption has been derived also.
The Band Structure of Rhodium and Its Relation to Photoemission Experiments
Authors: Christensen N. E. 
Published: July 2007

AbstractThe band structure of Rh has been calculated by means of the relativistic augmented plane wave method. The density of states, the joint density of states, and the energy distribution curves (EDC's) for photoemitted electrons were computed using the Gilat‐Raubenheimer integration technique. It is demonstrated that final‐state velocity modulation influences strongly the calculated EDC's through the mean free path of the excited electrons. Although this improves the agreement between theory and experiment the experimental lineshapes cannot be satisfactorily explained within the applied models. The results indicate that the present band calculation does not disagree with the optical experiments, but the photoemission process is too complex to be described in terms of the simple direct or non‐direct model.
Theory of Resolved and Unresolved Crystal Field Structure of ESR Spectra in Dilute Magnetic Alloys
Authors: Plefka T. 
Published: July 2007

AbstractThe influence of crystal fields on the dynamic transverse susceptibility of localized spin moments coupled to the conduction electrons in a metal is investigated. In Liouville‐space, the projector onto the subspace is introduced which is spanned by the transverse component of the conduction electron magnetization and the transition operators of the crystal field energy levels. Within the framework of projector formalism, the susceptibility is expressed in terms of a transition matrix which is then calculated in lowest order perturbation theory. The found explicit expression of the susceptibility is valid for the isothermal case as well as for the bottleneck one. The theoretical predicted resolved and unresolved ESR spectra are discussed for high and low temperature. For the bottleneck and the isothermal case, a resolved spectrum is expected when crystal field splittings are greater than the Korringa relaxation rate.
Optical Properties of CuGaS2 near the Fundamental Absorption Edge
Authors: Regolini J. L. , Lewonczuk S. , Ringeissen J. , Nikitine S. , Schwab C. 
Published: July 2007

AbstractThe absorption and reflection spectra of “green” and “orange” CuGaS2 crystals, prepared by chemical transport reaction, have been studied at low temperatures. The “orange” crystal presents an excitonic spectrum characteristic for intrinsic material. The triplet structure can be explained by comparison with CuCl. This configuration involves that the upper valence band, as in the case of cuprous halides, is formed by a mixing of p‐ and d‐like wave functions. The observation of a n‐ S h e by a wavelength modulation technique permits the calculation of the binding energy of the free exciton. The spectrum of the “green” sample, shifted towards the low‐energy side, is much more complicated. It is characteristic for a compound strongly perturbated by defects.
Spin Wave Spectrum and Magnetization of Magnetic Thin Films with a Rough Surface
Authors: Freese H. , Krey U. 
Published: July 2007

AbstractThe influence of the surface roughness on the low energy spin wave properties is treated within a quantized phenomenological spin wave theory. Up to second order in the roughness amplitude, the surface roughness can be replaced for thin films by a non‐local scattering Hamiltonian acting in two dimensions. For a surface with a random “mosaic structure”, results are obtained for the self‐energy of the magnons, for the density of states g(E), and for the magnetization as function of the temperature T. For rough films, due to the properties of g(E), the magnetization decreases faster with T than for a smooth film of equal thickness.
New Color Centers in KCl Crystals
Authors: Matsumura G. , Kuczynski G. C. 
Published: July 2007

AbstractNew absorption centers giving bands with maxima at 555 nm (Y) and 625 nm (Y′) at liquid‐nitrogen temperature, were observed in OH–containing KCl single crystals annealed in vacuum a t 600 °C and subsequently uv irradiated. The thermal bleaching of these bands yields F centers. Optical bleaching of Y′ yields increase of intensity of Y and F bands and vice versa. The Y and Y′ centers can be converted into F centers by compressing the crystal. This reaction is accompanied by emission of 460 nm light. Study of the effect of ambient atmospheres upon formation of these centers suggests the involvement of oxygen molecule ions present in the crystals.
Interband and Exciton Effects on Faraday Rotation near the Absorption Edge of CuCl
Authors: Suga S. , Koda T. , Mitani T. 
Published: July 2007

AbstractThe oscillatory behaviour of the Faraday rotation spectra near the absorption edge of CuCl is interpreted in terms of the interband and exciton effects. According to this interpretation, the positive Faraday rotation in low energy regions is predominantly due to the interband effect, while the large negative rotation a t energies just below the exciton absorption band is ascribed to the non‐rigid shift contribution of the exciton effect. Calculation based on this model is in satisfactory agreement with experiment. It is further suggested that the same effect will be also responsible for the similar oscillatory behaviour of the Faraday rotation observed in several semiconductors such as GaSb, GaAs, and CdTe.
Hyperfine Fields in Ferromagnetic Rare‐Earth Alloys
Authors: Guimaraes A. P. , Gomes A. A. 
Published: July 2007

AbstractThe hyperfine fields in ferromagnetic rare‐earth alloys are discussed assuming that the impurity concentration affects only the transferred hyperfine field, the effects on the band susceptibility being assumed to be small. The slope of the hyperfine field versus average spin in these alloys can be analysed in terms of this model; intermetallic systems like GdxY1−xAl2 are also considered. It is observed that the dominant contribution to the magnetization is due to d electrons, whereas the hyperfine field slope arises mostly from the interaction with the s electrons.
Temperature Dependence of Magnetoconductivity Tensor Coefficients in Pure Antimony Single Crystals at Low Temperatures
Authors: Bansal S. K. , Duggal V. P. 
Published: July 2007

AbstractFew of the galvancmagnetic measurements, at low magnetic fields, as a function of temperature in the interval 4.2 to 30 °K in single crystals of pure antimony are presented. The temperature dependence of anisotropy of magnetoresistance is discussed within the framework of two‐carrier multivalley band model of the Fermi surface. The temperature dependence of mobility of electrons and holes concluded from the low field measurements is in agreement with the results of strong field measurements.
Transverse Dember Effect and Anisotropy of Carrier Mobilities in Tellurium Single Crystals
Authors: Genzow D. 
Published: July 2007

AbstractNeasurenients have been made of the transverse Dember effect, photoelectromagnetic effect, Hall effect, and electrical conductivity of tellurium single crystals in the temperature range from 80 to 300 K. From this data information about magnitude and anisotropy of electron and hole mobilities have been deduced. The relaxation time for scattering of holes and electrons in tellurium single crystals without structure defects is nearly isotropic. The relaxation time for scattering by dislocations is characterized by the relation .
A Model of the Electrical Transport Phenomena in Imperfect Crystals of Copper Phthalocyanine. I. Basic Ideas and Treatment of Bulk Defects
Authors: Lehmann G. , Hamann C. 
Published: July 2007

AbstractStarting from the needed simplification of the problem a model is proposed, approximating the real crystal by molecule stacks, consisting of perfectly conducting molecule discs. In this way a band scheme is found, very similar t o the observed one. On the understanding that molecule stacks break off within the crystal and considering the molecule spatial extent and molecule orientation in CuPc, the perturbation levels in the crystals are computed. They are found in a good agreement with experimentally determinedtrap levels for electrons. The geometrical extent of the perturbation justifies the neglect of the perturbation interaction between adjacent piles.
The Diffusion of Mercury in Purified KCl and the Effect of OH− on Diffusion
Authors: Allen C. A. , Fredericks W. J. 
Published: July 2007

AbstractThe diffusion of mercury into both purified and hydroxide doped Kci was studied. The high vapor pressure of HgCI2 required modification of the usual technique to assure constant boundary conditions. The very low solubility of mercury made accurate determination of diffusion parameters difficult. Mercury diffuses into purified KCI over the temperature range from 449 to 549 °C in accordance with the relation Ds = 8.18 × 10−5 exp (−0.57 eV/kT). Over this same temperature range the free energy of association for the mercuric ion‐cation vacancy complex varies from 0.75 to 0.80 eV, an abnormally large value for this type of association. The presence of OH‐ causes extreme distortion of the concentration‐distance curve by forming a maximum in mercury concentration well away from the surface of the crystal. The maximum is thought to arise from the formation of the mercuric ion‐hydroxide ion compound identified optically in earlier studies.
Equivalent Quantum States in dn and d5+n Electronic Configurations
Authors: Langer J. M. 
Published: July 2007

AbstractIt is shown that for ligand fields in which the symmetries are subgroups of the full rotational group, the sequence and relative energies of the states with maximum spin are the same for dn and d5+n (n ≦ 5) configurations. Possibility of the generalization of this theorem t o other 1n and 121+1+n configurations is discussed. As an example, wave functions and relative energies for the crystal field d‐states in a tetrahedral environment are given.
Analysis of Uniaxial Stress Effect on the Free Exciton Line in GaAs
Authors: Lavallard P. 
Published: July 2007

AbstractPhotoluminescence from free excitons in GaAs has been studied by Gilleo et al. [4] for [100] stresses up to 500 kp cm−2. An analysis of their results is presented taking into account the spin‐exchange splitting of the exciton states and the variation with stress of the enveloppes functions of the exciton states. It is shown that the quasi‐cubic model can well explain the observed intensities of the lines.
Properties of Extraordinary Polaritons in LiNbO3
Authors: Posledovich M. , Winter F. X. , Borstel G. , Claw R. 
Published: July 2007

AbstractOn the basis of corrected assignments of the optical phonons in LiNbO3 the dispersion branches of extraordinary polaritons have been calculated for different wave vector directions with respect to the optic axis of the material. A fundamental feature of extraordinary polaritons is the lifting of crossing points between dispersion branches for wave vector directions different from the principal directions. A first experimental observation of this effect is presented and has been compared with theoretical data. Furthermore the experiments allow a simultaneous observation of the lowest frequency ordinary and extraordinary polariton branches.
Multiple Scattering Theory and Pseudogaps in Amorphous Covalent Semiconductors
Authors: John W. 
Published: July 2007

AbstractThe electronic density of states of amorphous covalent semiconductors is investigated using the multiple scattering theory of nonoverlapping muffin‐tin potentials. In the nearest neighbour approximation an expression is derived for the density of states which relates it to the density of states of a simple tight‐binding Hamiltonian. Numerical calculations for amorphous sps‐bonded C and amorphous Si show the existence of a pseudogap which is determinated by short‐range order.
Influence de la direction de propagation, par rapport au champ magnétique, sur l'atténuation d'ondes ultrasonores dans l'antimoniure d'in dium dégénéré
Authors: Prieur J.‐Y. 
Published: July 2007

AbstractNous présentons des résultats expérimentanx sur la variation de l'atténuation ultrasoliore avec l'angle entre le vecteur d'onde et le champ magnétique dans des cristaux d'antimoniure d'indium dégénérés. Nous montrons que les oscillations de Haas et van Alphen doivent ětre associées à celles u temps de relaxation. Une mesure du temps de relaxation eut proposée.
The Spin‐Wave Contributions to the Low‐Temperature Specific Heats of MnPt3 and FePd3
Authors: Anderson D. A. , Cragknell A. P. 
Published: July 2007

AbstractUsing the published results of inelastic neutron scattering experiments on MnP3 and FePd, we have calculated the spin‐wave contribution to the specific heat of each of these materials. While the results show aT3/2 temperature dependence at low temperatures. substantial deviations from this law were obtained for temperatures above about 10 K.