bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magneto‐Optics of Holes in the Presence of Internal Strains and Temperature in Single Quantum Well Structures
Authors: Singh M. , Tang S. Y. 
Published: July 2007

AbstractExpression are obtained for the frequency dependence conductivity tensor in the presence of a magnetic field and hole‐phonon interaction for p‐type single quantum well structures. From this one obtains the information about the transport and optical properties of single quantum well structures. The [4 × 4] Luttinger‐Kohn type of Hamiltonian is used to calculate Landau levels and Landau wave functions. Linear response theory is used to calculate the conductivity tensor and Green's function method is used to calculate the relaxation time (or Landau level broadening) due to hole‐phonon interaction. The [4 × 4] matrix interaction Hamiltonian is considered for the hole‐phonon interaction which includes the effects of internal strains arising from the mismatch of lattice constant or other defects. Selection rules Δn = ±3, Δn = ±1, are found and their corresponding probability amplitudes are obtained. Dispersional relations for magnetoplasma waves and elementary excitation are also given.
Anharmonic Phonon Frequency Shifts and Widths in Solid Deuterated Anthracene‐d10
Authors: Jordan J. F. J. , Kalus J. , Schmelzer U. , Eckold G. 
Published: July 2007

AbstractCoherent inelastic neutron scattering measurements of the temperature dependence of the frequency shifts and widths of some phonons in deuterated solid anthracene are presented. Calculations of the explicit anharmonic phonon frequency shift and the linewidth to the lowest order are described. It is assumed that the intermolecular potential is a pairwise sum of atom‐atom potentials. Using a 6‐exp potential, and potential parameters provided by Williams, the results for all external modes at the T point (q = 0) are calculated and compared with the available experimental data. A part of the anharmonicity of two internal modes is taken into account into the evalutaion. The results from the calculation agree with some of the measurements, but are different by about a factor of two for most of the phonons.
Raman Scattering in Nb–Cu Metallic Multilayers
Authors: Zhang Xing‐Kui , Xia Hua , Hu An 
Published: July 2007

AbstractRaman scattering by acoustic phonons is investigated in NbCu metallic multilayers grown by magnetron sputtering, with periods ranging from 1.7 to 20.0 nm. For larger‐periodic samples, many peaks which are analogous to those produced by Raman scattering by folded acoustic phonons in periodic superlattices, can be explained by using a perturbation elastic continuum model. On the other hand, in the samples which are layered polycrystals with textures two additional peaks at 158 and 198 cm−1 are observed and attributed to disorder‐activated transverse‐acoustic mode (DATA). The DATA shows an anomalous shift toward lower frequency as a function of film thickness and explains probably anomalies in the Rayleigh wave velocity versus modulated NbCu film thickness.
Investigation of the Transition between Large‐ and Small‐Radius Polarons in a One‐Dimensional Crystal
Authors: Feranchuk I. D. , Fisher S. I. , Komarov L. I. 
Published: July 2007

AbstractThe behaviour of the polaron characteristic in the intermediate range between large‐ and small‐radius approximation is considered for an one‐dimensional crystal. A discontinuous jump of the electron localization size is found. The influence of the lattice potential on the polaron characteristics is investigated.
A Theoretical Study of the FMR Surface Mode Excitation in Metals (Parallel Configuration)
Authors: Fraitová D. 
Published: July 2007

AbstractUsing the analytical FMR theory, the real part of the surface impedance as dependent on the magnetic field and surface anisotropy is calculated for two types of ferromagnetic metals with different exchange‐conductivity parameters. The shapes of the obtained two sets of FMR spectra (including the main and surface resonance modes) differ considerably; the discussion of the cause of this effect points to a pronounced influence of the FMR cross‐over region.
Electron Paramagnetic Resonance Study of the Dynamical Jahn‐Teller Effect on the 3d1 Impurities Ti3+ and V4+ in GaP
Authors: Kreissl J. , Ulrici W. , Gehlhoff W. 
Published: July 2007

AbstractThe EPR spectra of TiGa3+ and VGa4+ in GaP are studied at T = 20, 4.2, and 1.5 K. At 20 K the spectra are isotropic and become angular‐dependent for T ⪅ 4.2 K. By simulation of the spectra measured at T = 1.5 K this angular dependence is explained using the spin‐Hamiltonian for a 2E vibronic ground state arising from a weak‐to‐moderate E ⊗ ϵ dynamical Jahn‐Teller effect including internal random strains.
Electrical and Structural Properties of the Tungsten Bronze Bi4W20O62
Authors: Conan A. , Bonnet A. , Morsli M. 
Published: July 2007

AbstractTransport coefficient measurements (electrical conductivity and thermoelectric power) are performed on compact bars of a bismuth tungsten bronze compound Bi4W20O62 (labelled as B‐phase) in polycrystalline form over the temperature range 100 to 500 K. Experimental results are discussed in comparison with those obtained recently on a compound, labelled as A‐phase and which is prepared at a lower temperature. A single band model accounts for all the experimental results. The main differences which are observed in the electrical properties of the two phases are a consequence of the less disordered HTB and perovskite intergrowth sequences for the high‐temperature phase.
Quasi‐Classical Trajectory of Thermal Neutrons in Elastically Deformed Crystals
Authors: Lukáš P. , Kulda J. 
Published: July 2007

AbstractThe propagation of thermal neutrons through distorted crystals is reconsidered on the basis of an adiabatic quantum mechanical approach which enables one to derive quasi‐classical trajectories of neutrons for an arbitrary elastic deformation of a crystal. It is shown that the quasi‐classical concept is generally applicable even in the case when interbranch scattering takes place. For demonstration, the treatment is applied to a constant gradient deformation resulting in the well known hyperbolic trajectories of neutrons.
Two‐ and Three‐Body Forces in Lattice Dynamics and Elastic Behaviour of B.C.C. Calcium and Strontium
Authors: Aradhana K. , Rathore R. P. S. 
Published: July 2007

AbstractThe Morse potential is transformed to represent the three body couplings among the common nearest neighbours of the b.c.c. structure. These couplings which add to the present two body potential give rise to an effective potential which is employed to predict the phonon dispersion and second, third, and fourth order elastic constants it b.c.c. forms of calcium (Ca) and strontium (Sr). Recently reported neutron scattering data for these metals support the theoretical content of the model.
Electronic Energy Structure of Substoichiometric Molybdenum Carbides in Different Crystallographic Modifications
Authors: Bazhin I. V. , Kolpachev A. B. , Nikiforov I. Ya. 
Published: July 2007

AbstractIn terms of the multiple scattering theory using the crystalline muffin‐tin potential and taking into account the local distortion of the lattice the electronic structure of stoichiometric and nonstoichiometric molybdenum carbides MoC1−x for x = 0, 0.17, and 0.33 in cubic NaCl and hexagonal WC crystal structures is calculated. As the concentration of the carbon vacancies increases “atomization” of 2p states of carbon and growth of the Mo–Mo interaction take place. At the same time a new maximum of the electron density of states (DOS) appears at the carbon vacancies and in the metal d‐band near the Fermi level in cubic carbides. The Mo–Mo interaction is more important in the formation of DOS near the Fermi level of hexagonal carbides than in cubic ones. The DOS at the Fermi level depends essentially on the concentration of the carbon vacancies.
Aggregation of Bismuth in NaCl Crystals
Authors: Stoicescu Gh. , Nistor S. V. , Mateescu C. D. 
Published: July 2007

AbstractThe aggregation of Bi3+—vacancy dipoles in NaCl single crystals grown in a reactive atmosphere is studied by monitoring the changes in the intensity of the C‐band attributed to Bi3+ ions. An apparent third‐order reaction is observed to govern the aggregation process in the early stages, with an activation energy of 0.79 eV. No ESR signals attributed to Bi2+ centres are observed before or after X‐irradiation at 77 or 300 K.
Plasma Oscillations at the Surface of a Type II Superlattice
Authors: Sy H. K. 
Published: July 2007

AbstractSemi‐infinite type II semiconductor multilayers are investigated consisting of alternating layers of two‐dimensional electron and hole carriers. By applying electromagnetic boundary conditions, a dispersion relation is derived for surface plasma modes. This is shown to be equivalent to that obtained recently starting from electrostatic image charges. Some numerical results are also discussed.
Transverse Transport in n+GaAs/AlxGa1−xAs/n−GaAs Structures
Authors: Asche M. , Friedland K. , Kostial H. , Eaves L. , Sarbey O. G. 
Published: July 2007

AbstractThe dc current–voltage characteristics and the real and imaginary parts of the differential conductivity of a single barrier heterostructure based on n+GaAs/AlxGa1−xAs/n−GaAs are investigated. The temperature dependence of the modulated structure related to the emission of longitudinal optical phonons is measured in the region from 1.3 to 90 K and compared with microscopic models proposed to describe it. A detailed examination of the capacitance indicates the presence of an appreciable negative charge in the barrier or at its interface, but then the current and its temperature dependence can only by explained when additionally the presence of conducting channels in the barrier is assumed.
Supertransferred Hyperfine Fields at Nuclei of Diamagnetic Copper Ions in Chalcogenide Spinels Fe1−xCuxCr2S4
Authors: Fishman A. Ya. , Mitrofanov V. Ya. , Kovtun N. M. , Prokopenko V. K. , Shemyakov A. A. 
Published: July 2007

AbstractThe NMR method is applied to study the local fields at diamagnetic Cu+ ion nuclei in the magnetically ordered F1−xCuxCr2S4 (0 ≦ x ≦ 0.8) system. Additional transferred hyperfine fields are revealed at the Cu+ ion which are connected with orbital (pseudospin) moments of Fe2+ ions. The obtained results are interpreted qualitatively.
Magnetic Properties of Model Multicomponent Compounds of CsCl Structure
Authors: Adamian V. E. , Artsruni A. A. , Benaissa A. , Kocharian A. N. , Melikian M. A. , Toneian A. G. 
Published: July 2007

AbstractThe solid solutions of CsCl type structure with controllable parameters (concentration of magnetic ions, number of conduction electrons per unit cell, and lattice parameter) are synthesized. In the systems investigated either one of the parameters is changed or all the three parameters are retained constant at different alloy compositions. X‐ray phase analysis is carried out and the magnetic properties of the alloys are investigated. The results are discussed in the approximation of the RKKY theory.
Microscopic Model of Metastable Changes in Hydrogenated Amorphous Silicon
Authors: Chen Y. F. , Wong C. K. 
Published: July 2007

AbstractConcepts based on the two‐level system of structural excitations have not accounted satisfactorily for many metastable changes in hydrogenated amorphous silicon. Defects created at higher temperatures are more difficult to anneal out. Photoluminescence decreases much more after irradiation at 77 K than it does after irradiation at 300 K. After rapid cooling from 483 K, the spin signal grows with time at room temperature, etc. A microscopic explanation of these and other phenomena is given in terms of a three‐level system of structural excitations: initial state, weak SiSi bond; intermediate metastable state, SiHSi bond; final metastable state, SiH and Si dangling bond.
Eu2+‐Mn2+ Energy Transfer in NaCl and KCl Crystals
Authors: Cywiński R. , Mügeński E. , Sokólska I. 
Published: July 2007

AbstractIt is shown that excitation energy transfer in doubly doped (Eu2+‐donor, Mn2+‐acceptor) KCl and NaCl crystals proceeds due to the presence of various aggregation products containing both dopant ions. In simple aggregates composed of Eu2+–cation‐vacancy and Mn2+–cation‐vacancy dipoles a single stage energy transfer Eu2+‐Mn2+ is proposed due to the multipole interaction (most probably of dipole–quadrupole type) or due to exchange interaction. In the case of Eu2+‐rich precipitates with built‐in Mn2+ ions, the energy transfer, after preceded energy diffusion in the donor system, is determined by the contribution of the phonons (phonon absorption in NaCl and phonon emission in KCl) and exchange interactions.
Amplification of Acoustic Waves in Magnetised High Resistivity Piezoelectric Semiconductors. Effect of Nonuniform Electric Field Intensity and Carrier Concentration
Authors: Dey (Bose) M. , Ghosh S. 
Published: July 2007

AbstractA theory of the amplification of an acoustic wave in a high resistivity piezoelectric semiconductor in the presence of a longitudinal dc electric field and a transverse magnetostatic field is developed. The static electric field intensity and the carrier concentration inside the semiconductor are taken as nonuniform even in trap‐free samples. This assumption used in the theory modifies the results obtained by the earlier theories considerably. It is also shown that this nonuniformity can explain the experimentally found asymmetric attenuation characteristic curves. Numerical estimations are made for n‐CdS at 300 K. It is found that a weak magnetic field does not have any remarkable effect on amplification, but a higher magnetic field sharply reduces the gain.
Energy Transfer of Electron Excitation. Decay Kinetics of Exciton Luminescence in a Three‐Layer System
Authors: Pokutnyi S. I. 
Published: July 2007

AbstractThe decay kinetics of exciton luminescence in impurity molecules in a three‐layer system near the interface of dielectric media in the presence of energy transfer of electron excitation is considered. It is shown that a change in the functional dependence of the probability of Förster energy transfer leads to new characteristic dependences in the decay kinetics of impurity luminescence in layered structures.
Critical Behaviour of Semiconductor Spin Glasses (CuCr2Se4)x (Cu0.5Me0.5Cr2Se4)1−x (Me = In, Ga; 0 ≦ x < 0.1)
Authors: Koroleva L. I. , Virovets T. V. 
Published: July 2007

AbstractMagnetic susceptibility behaviour is studied in weak dc and ac magnetic fields in the spin glass–paramagnetism transition region of the system (CuCr2Se4)x (Cu0.5Me0.5Cr2Se4)1−x (Me = In, Ga). The critical exponents γ, δ, and β in the spin glasses with x = 0,0.01 and 0.03 (Me = In) determined from the nonlinear static susceptibility χnl in the region of the freezing temperature T′f are in close agreement with values predicted by the mean field theory, Tf being determined by the maximum value of χnl. The experimental points χnl satisfactorily fit the scaling function in the critical range H < 30 Oe and (T − Tf)/Tf < 0.4. The freezing temperature T′f of spin glasses with 0 < x < 0.05 (Me = In, Ga), determined from the maximum initial susceptibility in the ac field depends on the measurement frequency according to the Vogel‐Fulcher law. The constant T0 in this law is close to Tf. The fact that static scaling relation and the Vogel‐Fulcher law hold for T′f indicates that spin glass–paramagnetism phase transition occurs in the spin glasses concerned.
Calculation of Self‐Interstitial Formation Energy (Both Split and Non‐Split) in Noble Metals
Authors: Bandyopadhyay A. K. , Sen S. K. 
Published: July 2007

AbstractThe energy of formation of different interstitial configurations in f.c.c. metals using pseudopotential approach is formulated. A model calculation is done with a Ashcroft‐Hubbard model potential for copper, silver, and gold. The calculation is indicates that the (100) split configuration is most stable and has a minimum energy which is consistent with other theoretical predictions and experimental observations.
Global Wave Mode Theory for the Formation of Dendritic Structure on a Growing Needle Crystal
Authors: Xu Jian‐Jun 
Published: July 2007

AbstractAn investigation is made of the global instability mechanisms of dendritic crystal growth. In previous papers a global instability mechanism is explored which is called WEASR‐mechanism and the related global WEASR‐modes are derived. In this paper, another global instability mechanism is shown and its related global mode solution is derived, called global trapped wave (GTW)‐ mode. The quantum condition is obtained. A self‐sustaining GTW‐mode is found. This wave mode theory well explains the origin and persistence of the micro‐structure in dendritic growth.
Surface Relief and Dissipation Influence on Plasmon–Phonon Polariton Dispersion of Polar Semiconductors
Authors: Dmitruk N. L. , Fidrya N. A. , Snitko O. V. , Venger E. F. 
Published: July 2007

AbstractThe effect of the surface roughness by plasmon‐phonon attenuation on the surface mixed polariton (SP) dispersion is theoretically investigated. It is shown that the dispersions curve displacement is a nonmonotonous function of the attenuation in the presence of surface roughness. Epitaxial n–n+ GaAs layers are investigated experimentally by the ATR method.
On the Mechanism of Two‐Photon Absorption by Nd3+ Ions in Yttrium Aluminium Garnet and Yttrium Lithium Fluoride in the Region of 1.06 μm
Authors: Makhanek A. G. 
Published: July 2007

AbstractA calculation is made of two‐photon absorption (TPA) cross‐sections by Nd3+ ions in YAG and YLF crystals in the region of 1.06 μm. It is shown that the experimental results are in good agreement with the general theory taking into account the TPA polarization characteristics and effects (for YAG‐crystals) of surrounding ligands on the TPA process. It is found that the lowest Stark component of the Nd3+ ground term in YLF does not correspond to the symmetry type earlier proposed and a new identification is given.
Theory of the Single Ion Magnetocrystalline Anisotropy of 3d Ions
Authors: Xu You , Yang Gui‐Ling , Chu Da‐Ping , Zhai Hong‐Ru 
Published: July 2007

AbstractMethods for calculating the single ion magnetocrystalline anisotropy of 3d ions in the crystal field with threefold axis or higher symmetry and lower symmetry are given. Using these methods, the contributions of Fe3+ ions at all the five crystal sites of Ba‐ferrite (BaM) to the magnetocrystalline anisotropy constants and their temperature dependence are calculated. Also calculated is the single ion anisotropy of the Co2+ ion substituting the Fe3+ ion at the 12k site. The results agree well with experiments.
Phase Transition in Rb3H(SeO4)2‐Type Crystals. I. The Symmetry Analysis of Proton Ordering
Authors: Salejda W. , Dzhavadov N. A. 
Published: July 2007

AbstractProton ordering is analysed at the phase transition in superionic crystals of the type Rb3H(SeO4)2. The method of concentration waves is applied. The observed ordering of protons is described using basis functions of the irreducible representations of the groups of wave vectors at the L and Γ points of the Brillouin zone. Possible directions of the crystallographic axes of the low‐temperature phase are determined in the framework of the approach proposed. The jump of entropy is calculated. The results obtained are in good agreement with experiment.
The Electronic Structure of the Alkaline‐Earth Oxides. I. The Differences between MgO and LiF, NaF Electronic Structures
Authors: Lobatch V. A. , Kulyabin B. E. , Zhukov V. P. , Medvedeva N. I. 
Published: July 2007

AbstractThe energy band structures of MgO, LiF, and NaF are calculated by the LMTO method with a set of different atomic spheres radii. It is shown that MgO is distinct from fluorides in that a pure ionic charge distribution is not achieved. Such a behaviour of the electron density is explained by the presence of a potential barier inside the oxygen atomic sphere near its boundary. As a consequence the charge configuration of MgO is suggested to be close to Mg2+O− plus one electron distributed in the interionic region.
Compton Profile Anisotropies of GaAs
Authors: Panda B. K. , Mahapatra D. P. , Padhi H. C. 
Published: July 2007

AbstractDirectional Compton profiles along the [100] and [111] directions of GaAs are measured using 59.54 keV γ‐rays from a 3 Ci241 Am annular source. A pseudo‐potential calculation is performed to calculate the Compton profile and autocorrelation anisotropies. Inclusion of a non‐local term in the pseudopotential appears to give better agreement with experimental result. The calculated period of the oscillatory anisotropy tends to be shorter than that experimentally observed. The experimental autocorrelation anisotropy has a small peak near the origin which is not accounted for by the theory.
Electronic Structure of F‐Centers in LiH by the SCF Xα Method
Authors: Takeuchi T. 
Published: July 2007

AbstractThe electronic structure of F‐centers in LiH is obtained by SCF Xα method. The F‐center transition energy is found to be 4.76 eV. Differences between the electronic structure of F‐centers in ionic oxides and that in LiH are discussed.
Optical Absorption near Excitonic Resonance of MOCVD‐Grown ZnSe Single Crystals
Authors: Gribkovskii V. P. , Zimin L. G. , Gaponenko S. V. , Malinovskii I. E. , Kuznetsov P. I. , Yakushcheva G. G. 
Published: July 2007

AbstractThe exciton and band‐to‐band absorption spectra of monocrystalline ZnSe films produced by MOCVD‐technique on GaAs substrates are studied in the temperature interval 80 to 300 K by laser spectroscopy technique. Violation of the Bouguer law and the temperature dependence of the integral absorption coefficient in the region of the excitonic band are revealed. The distinctive features of the transmission spectra near the excitonic resonance are interpreted in terms of the polaritonic approach to light propagation in crystals.
On the Possibility of Describing Lattice Properties of Iridium in Terms of Pseudopotential Theory
Authors: Greenberg B. A. , Katsnelson M. I. , Koreshkov V. G. , Osetskii Yu. N. , Peschanskikh G. V. , Trefilov A. V. , Shamanaev Yu. F. , Yakovenkova L. I. 
Published: July 2007

AbstractThe possibility is discussed of describing lattice properties of iridium in terms of pseudopotential perturbation theory with allowance for second and third order. Values of pseudopotential parameters are proposed which provide a good description of the lattice properties of iridium under zero pressure, the contributions of the three‐ion forces being small. The total energy, pressure, elastic moduli, Debye temperature, low‐temperature Grüneisen parameter, pairwise potentials, and also effective solid sphere packing parameters are calculated. In addition, by invoking molecular dynamic methods, the vacancy formation and migration energies and the stacking fault energies are computed. The electron energy spectrum and group velocity calculations suggest that the electron density of states curve of Ir exhibits no van Hove singularities near the Fermi level, a fact which apparently accounts for the successful description of lattice properties in terms of the pseudopotential perturbation theory.
Two‐Band Envelope Function Model for Graded Interfaces
Authors: Rodríguez‐Coppola H. , Martínez‐Cuellar J. L. , Pérez‐Álvarez R. 
Published: July 2007

AbstractAn analytical calculation is given of the energy minibands of a superlattice with graded interfaces and the sawtooth superlattice applying a simple two band model to describe electrons in coduction band and light holes, and a single band equation for heavey holes with good agreement with calculations reported before. The effective energy gap in the superlattice with graded layers as a function of the thickness of the graded interfaces shows a different behavior than reported before for small superlattice period. It is shown that with simple enough envelope function models such composite graded systems can be treated with good results.