bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron spin resonance on V2O5: Cr3 +1
Authors: Sperlich G. , Jansen K. 
Published: July 2007

AbstractThe ESR spectrum of Cr3 + ions, substituting V5 + ions in V2O5 single crystals, can be described by the conventional spin Hamiltonian with (at room temperature) gx = gy = 1.959; gz = 1.972; D = + 21.077 GHz; E= 0.47 GHz. The unusually strong temperature dependence of the parameter D is compared with that of SnO2 :Cr3 +.
Etude des centres colorés qui apparaissent dans un cristal de chlorure de strontium dope avec un ion alcalin
Authors: Baltog Par I. , Lefeant S. , Houlier B. , Yuste M. , Chapelle J.‐P. 
Published: July 2007

AbstractAprès irradiation aux rayons à B 90 °K, on obtient un signal R.P.E. dǔ à des centres Vk orientés suivant [001] et un spectre d'absorption optique que nous attribuons à des centres Vk, des centres F* perturbés et des associations de centres F. La largeur des raies du signal R.P.E. est attribuée à l'interaction des centres Vk et des cations alcalins. Cette interaction cesse par chauffaée à 160 °K ce qui montre qu'à cette température les centres Vk devienncnt mobiles. Par chauffage, les centres F* perturbés donnnent naissance à des associations, puis cellcs‐ci fournissent des centres F non perturbès. Le modèle proposé rend compte des phénomènes qui ont été observés dans CaF2:Na+ après irradiation aux rayons X.
Thermal Conductivity of Gadolinium Monosulphide
Authors: Khusnutdinova V. , Oskotspii V. S. , Smirnov I. A. , Sergeeva V. M. 
Published: July 2007

AbstractThe thermal conductivity of gadolinium monosulphidc was measured within the temperature range of 80 to 720 °K. The lattice part of the thermal conductivity (XL) mas determined. It is difficult to explain the temperature dependence of xL, theoretically taking the phonon scattering by conduction clcctrons into account contrary to the case of the lanthanum monochalcogenides. The additional lattice thermal resistivity in GdS is attributed to phonon scattering on the paramagnetic statcs of Gd ions in the crystal field.
The inelastic nature of diffuse X‐Ray scattering near the α‐β transition in quartz
Authors: Bauer K. H. W. , Jagodzinski H. , Dorner B. , Grimm H. 
Published: July 2007

AbstractBy inelastic scattering of neutrons, the origin of diffuse X‐ray scattering along [ζ00] directions has been investigated. Phonon frequencies are found to be anisotropic and especially low for the [ζ00] direction. Phonons with low frequencies cause enhanced X‐ray scattering in pronounced diffuse streaks. It is probable that this occurs because a soft optic phonon, which drives the α‐β transition and which has been investigated at q = 0 by other authors, becomes soft very predominantly for the [ζ00] direction and forces down an acoustic dispersion branch. The measured phonons are strongly damped at 560 °C (13° below the transition) so that there is a remarkable tail at zero energy transfer, but elastic scattering as expected from static disorder was not observed. The dispersion for deviations from the [ζ00] direction shows a steep valley, which explains the width of the diffuse scattering perpendicular to the [ζ00] direction.
Studies of photoluminescence in GaAs1−xPx mixed crystals
Authors: Gaj J. A. , Majerfeld A. , Pearson G. L. 
Published: July 2007

AbstractPhotoluminescence measurements on GaAs1−xPx single crystals were performed for the composition range 0.27 < x < 0.44 throughout the spectral region 0.6 < λ < 0.8 μm at temperatures between 5 and 125 °K. Four luminescence bands A, B, C, and D were found. The suggested identification is: B hand‐to‐band transitions, B and C conduction band‐to‐acceptor level transitions, and D distant donor‐acceptor pair recombination. The deep donor level, introduced by S in this composition range, was found to follow the indirect gap variation with composition.
Non‐equilibrium plasma in semiconductors with anisotropic band structure
Authors: Dykman I. M. , Tomchuk P. M. 
Published: July 2007

AbstractOscillations of the non‐equilibrium plasma in semiconductors with anisotropic band structure like p‐type Ge are studied. The non‐equilibrium of the plasma is caused by a sufficiently large external electric field. A high‐frequency contribution (due to the field of the oscillations) to the carrier distribution function is found from the kinetic equation taking account the scattering anisotropy and spatial dispersion. The dependences of the frequency and damping constant of the eigenoscillations on the magnitude and orientation of the constant field are determined. A summary of the results obtained and of the proposed experiments is given at the end of the paper.
Jahn‐teller structure in 3A2(3F) → 3T1 (3F) absorption band of CdS:Ti2+
Authors: Boyn R. , Ruszczynski G. 
Published: July 2007

AbstractThe absorption spectrum of Ti2+ centres in CdS betwccn 0.3 and 1.5 eV is measured in the temperature range 10 to 295 °K The spectrum can be explained on the basis of crystal‐field theory. A detailed analysis of the temperature dependence of the 3A2, → 3T1 (3F) band shows that the triplet structure of this band is due to strong interaction with τ2 type vibrational modes of phonon energy 3.3 meV. This analysis is based on the theory of Toyozawa and Inoue [6] and the method of moments of Henry et al. [14]. Effects of the autoionization of the 3T1 state (which has been shown to be located in the conduction band [13]) are believed to be seen at low temperatures.
Anomalous polarisation current in alkali halide crystals
Authors: Harris L. B. 
Published: July 2007

AbstractIn low temperature de polarisation of alkali halide crystals current sometimes flows in the opposite direction to that normally observed. This anomalous current, which is small and not due to electret effect, appears to be a flow of conduction charge in surface layers, observed only when the processes causing conventional polarisation are minimal. The crystal surface acts as though it contains a negative capacitance that stores a layer of anomalous charge, whilst normal charge tends to form peripherally around guard‐ring electrodes. Polarisation is largely a surface effect, having little relation to bulk crystal properties.
Structure magnétique ordonnée du composé DyCu
Authors: Wintenberger Par M. , Chamard‐Bois R. , Belakhovsky M. , Pierre Et J. 
Published: July 2007

AbstractLe composé DyCu a été étudié par diffraction neutronique sur poudre. Le diagramme observé laisse subsister une indétermination entre une structure colinéaire avec les moments parallèles à un axe quaternaire et une structure non colinéaire avec les moments portés par les axes ternaires. L'étude du champ cristallin, de l'énergie dipolaire et celle de l'effet Mössbauer [1] sont en faveur de ce dérnier type de structure.
Tunable stimulated spin‐flip raman scattering in InSb at various wavelengths
Authors: Irslikger C. , Grisar R. , Wachernig H. , Häfelf H. G. , Smith S. D. 
Published: July 2007

AbstractTunable stimulated spin‐flip Raman scattering from conduction electrons in InSb is investigated at four different pump wavelengths (10.6, 10.2, 5.3, 5.1 μm). The tunable frequency range of the Raman‐scattered radiation is increased. Output powers of the Raman‐scattered light as a function of input power densities and magnetic fields were measured for the mentioned pump wavelengths. Thresholds for stimulated scattering were determined. From these the gain factors were calculated. The expected resonance in the 5 μm region is seen in the results and leads to extremely low thresholds and high gain factors.
π‐electron absorption spectra in free‐base phthalocyanine and porphyrin
Authors: Mathur S. C. , Singh J. , Kumar H. 
Published: July 2007

Abstractπ‐electron absorption spectra in the range 14000 to 60000 cm−1, in free‐base phthalocyanine and porphyrin have been calculated using molecular orbitals method. The new transitions beyond the Soret band observed by Schechtman and Spicer [5] and Edwards and Gouterman [6], in phthalocyanines, are explained.
On the effect of overlapping and covalency on the optical spectra of impurity ions in dielectric crystals
Authors: Cherepanov V. I. , Krotkii A. I. , Shchetkov A. A. 
Published: July 2007

AbstractThe influence of overlapping and covalency on the interelectronic correlation parameters of impurity ions with 3dN (N = 2, 3, 7, 8) configuration in octahedral complexes is considered using the MO‐LCAO approximation. It was shown that in addition to a decrease of the usual Slater parameters F0, F2, F4, these effects lead to the appearance of additional parameters. The meaning of these parameters is discussed. Numerical calculations are made for the complexes V3+O, Cr3+F, Ni2+F, Co2+F.
Energy loss of hot carriers due to optical phonons in degenerate nonpolar semiconductors
Authors: Tschulena G. R. , Keil R. 
Published: July 2007

AbstractAn expression is derived for the average rate of energy loss of hot carriers scattered by optical phonons in degenerate nonpolar semiconductors. A discussion of the influence of degeneracy for the particular case of n‐type germanium is presented. The influence of degeneracy on the energy relaxation time is estimated.
Ultrasonic attenuation in p‐Type Gasb at microwave frequencies
Authors: Bougnot G. , Galibert G. , Desfours J. P. 
Published: July 2007

AbstractAn investigation is made of the variation of the attenuation coefficient for shear and longitudinal ultrasonic waves which propagate through monocrystalline p‐type Gasb. The study was carried out for frequencies ranging from 0.5 to 1 GHz and in a range of temperatures from 5 to 300 °K. The measurements made by the pulse echo method are then compared with the theory of Woodruff and Ehrenreich and that of Bommel and Dransfeld.
Magneto‐optical anisotropy in nickel
Authors: Parker M. R. 
Published: July 2007

AbstractThe permittivity tensor normally employed in macroscopic magneto‐optical theory of magnetic media, based solely upon considerations of the effects of spin–orbit coupling, is inadequate in providing a complete theoretical description of the magneto‐optical behaviour of single crystal nickel. It is shown here that the observed dependence of its magneto‐optical behaviour on crystallographic orientation can be explained satisfactorily by considering, in addition to the effects of spin–orbit coupling, the anisotropic effects of magnetostriction on the optical constants of the medium.
ENDOR investigations of Cr+ centres in NaF, NaCl, and NaBr
Authors: Ziegler H. 
Published: July 2007

AbstractIsolated paramagnetic Cr+ centres in sodium halide crystals are studied by EPR and ENDOR. They show cubic symmetry. Superhyperfine and quadrupole interactions with many neighbouring ions (up to 〈300〉 in NaF) could be determined. The experimental results are interpreted in terms of two models for the wavefunction of the centre: overlap and covalency. A new way for the experimental determination of the coefficients for σ‐ and π‐covalency, using the isotropic superhyperfine interactions of neighbours 〈110〉 and 〈200〉, is proposed. The small anisotropic superhyperfine interaction of the nearest neighbours, which becomes even negative for Br− in NaBr, cannot be understood along these lines.
Mössbauer spectra of 57Fe in Fe1−xCoxSi and Fe1−xNixSi
Authors: Dubovtsev I. A. , Sidorenko F. A. , Bortnik A. N. , Shubina T. S. , Filippova N. P. 
Published: July 2007

AbstractMössbauer spectra of 57Fe in Fe1−xCoxSi and Fe1−xNixSi have been investigated as a function of composition and temperature. Substitution of Fe by Co and Ni increases the isomer shift throughout the temperature range studied. Composition dependence of the quadrupole splitting correlates reasonably well with similar dependences specific to other physical characteristics of these alloys. Rise of temperature is accompanied by a decrease of quadrupole splitting in the range of temperatures involved. The results of the study are used to discuss the type of energy band.
Self‐diffusion of cesium‐134 and diffusion of rubidium‐86 in cesium iodide single crystals
Authors: Klotsman S. M. , Polikarpova I. P. , Timofeev A. N. 
Published: July 2007

AbstractThe self‐diffusion of Cs‐134 and the diffusion of Rb‐86 in CsI single crystals were measured in the temperature range 404 to 603 °C using the tracer‐sectioning technique. The temperature dependencies of diffusion coefficients are D = (17.6) exp [−(35460 ± 140)/RT] cm2 s−1 for Cs‐134 and D = (27.3−2.7+3.0) exp [−(34540 ± 160)/RT] cm2 s−1 for Rb‐86. Comparison of present data with earlier results on diffusion parameters of Na‐22 in CsI single crystals shows that there is no dependence of the activation energy Q on characteristics of the homovalent impurities. On the other hand, the pre‐exponential factor D0 increases steadily with decreasing ion radius of the diffusing cations. The independence of Q on homovalent impurity characteristics is in qualitative agreement with known anomalous properties of cations with small ion radii in alkali halide crystals and with the expected temperature dependence of the correiation factor.
Continuum elasticity calculation of the electric field gradient around point defects in KBr and KI
Authors: Muggli J. 
Published: July 2007

AbstractThe strain field in alkali halide crystals containing low concentrations of substitutional alkali or halide ions is calculated with the help of anisotropic continuum elasticity theory using Vegard's rule. The gradient elastic tensor S for KBr and KI is derived from a comparison with experimental shifts of NMR lines. It is found that continuum theory can describe the field gradient at ion sites as near as [300] and [110] as seen from the defect and can explain critical sphere measurements.
Investigation of the stability of the Si III and Ge III crystal structures using force constants
Authors: Weaire D. , Williams A. R. 
Published: July 2007

AbstractThe metastable crystalline phases of Si and Ge, known as Si III and Ge III, offer an interesting test of the force constant models currently being applied to the study of amorphous Si and Ge, since they are made up of distorted tetrahedral bonds. It is found that, using force constants depending only on the bond lengths and angles (adjusted to fit the phonon spectrum of the diamond cubic structure by Singh and Dayal), minimisation of the total energy gives structures and densities fairly close to the observed values for these phases. However, the magnitude of the total energy, relative to the diamond cubic structure, appears to be much too large and some caution seems advisable in applying this or similar models to the calculation of the heat of crystallisation of amorphous semiconductors.
A perturbation‐theoretical treatment of the time‐dependent Boltzmann equation for crystal electrons in a strong electric field
Authors: Henneberger K. , Röseler J. 
Published: July 2007

AbstractThe properties of the time‐dependent distribution function, particularly the possibility of formation of Zener oscillations, are investigated. Hereby the Boltzmann equation is reduced to an eigenvalue problem. In addition to general investigations, a perturbation‐theoretical method for the calculation of the eigenfunctions and the eigenvalues in the strong‐field limit is given. The restriction to the first terms of the perturbation‐theoretical expansion is allowed, if and only if Zener oscillations exist relatively unperturbed. This is possible for electric field strengths which satisfy the rough condition

Using an exactly solvable but nontrivial model, the results found by general considerations can finally be confirmed and completed.
The theory of the Borrmann dislocation contrast
Authors: Tikhonova E. A. 
Published: July 2007

AbstractThe equations of the dynamical scattering theory are derived for a crystal with slowly varying distortion using a method analogous to the WKB method in the quasiclassical approximation. In the zeroth approximation in h a system of two equations is obtained. The local dispersion equation determines the eikonals of the wave functions. The equation in the first approximation is derived under the assumption that only one function determines the change of the amplitudes. The system of equations is not complete but allows to determine in absorbing crystals the change of the electron current component which extends along the reflecting plane and is principally apparent in the formation of Borrmann dislocation contrast. The obtained equations are valid as well far from the dislocation as close to it. The contrast of screw dislocations parallel to the crystal surface is considered.
Calculated phonon spectra and INS cross sections of MgZn2
Authors: Eschrig H. , Urwank P. , Wonn H. 
Published: July 2007

AbstractThe phonon spectra of the Laves phase of C14 structure (AB2‐type intermetallic compounds) and the inelastic neutron scattering cross section according to the creation and annihilation of phonons are investigated using group theory. For MgZn2 model potential calculations of phonon spectra are made along the line of highest symmetry in the Brillouin zone using Shaw's potential. Very low lying optical branches are found.
The effect of alloying on the energy gap of a semiconductor: Calculations for Pb1−xSnxTe and Pb1−xGexTe
Authors: Wexler G. , Morgan G. J. 
Published: July 2007

AbstractSimple calculations have been made of the shift in the energy gap in PbTe when alloyed with small amounts of Sn and Ge. The calculated energy shifts, which are of opposite sign for these two systems, are in rough agreement with experiment [1,2]. They are the sums of contributions produced by the strain field, the change in the short‐range potential, and the change in the relativistic energy. A variational method has been used, containing a trial function based on published details of the wave functions in PbTe.
Theory of disordered systems. I. The functional average
Authors: Fischbeck H. J. 
Published: July 2007

AbstractA theory of disordered systems of noninteracting electrons is derived from the Gaussian functional average over fluctuating potentials. The basic assumption is that the statistical properties of the random potential are solely characterized by its autocorrelation. This theory proves to be formally equivalent to a many‐particle theory with two‐particle interaction, in which the autocorrelation plays the part of the formal interaction. As illustration two simple models are considered. Their density of states, conductivity, and mobility are calculated.
Rotational hysteresis in MgFe and NiFe ferrites with antiferromagnetic precipitate
Authors: Maxim Gh. 
Published: July 2007

AbstractIt is shown that the rotational hysteresis at high fields of the MgFe and NiFe ferrites increases strongly with the concentration of the antiferromagnetic NiO or α‐Fe2O3 precipitate. This influence is explained by the ferrimagnetic‐antiferromagnetic exchange interaction. A new method for evidencing antiferromagnetic precipitates in ferrites is proposed.
Impurity conductivity in low compensated semiconductors
Authors: Efros A. L. , Shklovskii B. I. , Yanchev I. Y. 
Published: July 2007

AbstractA theory of the temperature and concentration dependence of the impurity conduction in low compensated semiconductors is presented. For the activation energy the expression ε3 = 0.99 (e2/x)N (1 − 0.43 v K1/4) is derived, where ND is the majority impurity concentration, K is the degree of compensation, and v is a numerical factor whose value is likely to be about 0.7. This expression essentially differs from the well known result of Miller and Abrahams. It is shown that the above dependence isin good agreement with available experimental data.
Thermoelectric effects of heavily doped semiconductors at low temperatures
Authors: van Cong H. , Mesnard G. 
Published: July 2007

AbstractUsing the Green function methods, in the Feynman‐path integral formulation, applied to disordered systems and developed already in four previous papers, the thermoelectric effects at low temperatures are studied from a simplified model of heavily doped semiconductors. Two typical cases concerning the relation between the carrier and the donor concentrations are discussed.
Stationary kink motion in the secondary Peierls relief
Authors: Alshits V. I. , Indenbom V. L. , Shtolberg A. A. 
Published: July 2007

AbstractThe problem of stationary kink motion in the secondary Peierls relief has been solved in a self‐consistent procedure. The radiation damping of a kink was studied as a function of its average velocity v and of the relief height. It is shown that at high velocities the kink ernits energy mainly on the basic harmonic, and that the radiation damping is proportional to 1/w. With decreasing velocity v the increase in the degree of non‐uniformity of the kink motion results in a broadening of the radiation spectrum and in the growth of the dissipation. The decrease of the velocity v is possible only up to some critical “starting” velocity below which a stationary kink motion is not realized. A dependence of the starting velocity on the relief height and kink width has been found. The phenomenon of the critical velocity is observed also under conditions of viscous dissipation. In this case the starting velocity decreases with increasing viscosity a and vanishes above some threshold value α. USSRAt α > αc the effect of the “dry friction” type is predicted: With decreasing velocity the dynamic kink damping tends to the static Peierls stress and does not vanish at v = 0. Possible display of the starting velocity effect in the experiment has been indicated.
Theoretically predictable effects and new interpretations in spin wave resonance of thin films with asymmetric boundary conditions
Authors: Puszkarski H. 
Published: July 2007

AbstractThe eigenvalue problem of the finite linear chain with arbitrary asymmetric boundary conditions is solved strictly. The results are used in quantum theory of spin wave resonance (SWR) in thin asymmetric ferromagnetic films. A theory providing some new interpretations of experimentally known effects in SWR and predicting new as yet unobserved effects is proposed. The results are visualized in an especial surface pinning diagram which should prove highly useful for the comparison of experimental data with the theory.
Circular prismatic dislocation loop in a two‐phase material
Authors: Dundurs J. , Salamon N. J. 
Published: July 2007

AbstractThe elastic fields of a circular prismatic dislocation loop in a two‐phase material are evaluated to arrive at the elastic energy and Peach‐Koehler force. The results can be expressed in terms of complete elliptic integrals. The asymptotic forms reveal that the interaction between the prismatic loop and the second phase is not necessarily restricted to simple repulsion or attraction, and that for certain combinations of the elastic constants stable or unstable equilibrium positions are possible.
A theory of the heat of transport of ionic solids using a linear chain model
Authors: Boswarva I. M. , Tan P. L. 
Published: July 2007

AbstractBoth the transition state theory and the kinetic theory for thermal diffusion fail to explain simultaneously the magnitude and the temperature dependence of the heat of transport. The linear chain model, developed in this paper, removes the limitations of the other two theories and it is successful in explaining the experimental data for the silver halides.
Intrinsic localized surface states in GaAs
Authors: Ball G. , Morgan D. J. 
Published: July 2007

AbstractSurface states at the cleavage plane of GaAs with energy in the band gap of the bulk band structure and with wave vector corresponding to the point γ at the centre of the [110] surface Brillouin zone are calculated using the empirical pseudopotential method, K · p theory, and the method of matching wavefunctions. The results differ markedly from those previously reported for GaAs in that, when the matching plane is situated midway between two atomic layers, not one but two localized surface states are found. When the matching plane is displaced from the central position, however, one of these localized states disappears from the band gap.