bluuebunny/crossref_metadata_2025_split huggingface dataset:
Volume Dependence of Dielectric Properties of Some Fluorite‐Structure Crystals
Authors: Dutt N. , Agrawal G. G. , Shanker J. 
Published: July 2007

AbstractThe experimental data on first and second order pressure derivatives of dielectric constants are used to make an analysis of the volume dependence of polarizabilities, effective charge parameter, and transverse‐optic‐mode frequencies in CaF2, SrF2, BaF2, PbF2, Sr(NO3)2, Ba(NO3)2, and Pb(NO3)2. The short range force constant responsible for the ion‐displacement polarizability is calculated with the help of Lundqvist's three‐body interaction model. Reasonable values for the volume derivatives of various dielectric parameters are obtained. Values of optic‐mode‐Grüneisen parameters and their volume derivatives are also calculated and compared with available experimental data.
The Random Field Ising Model in 2 + ϵ Dimensions Critical Behaviour from Interface Fluctuations
Authors: Nattermann Th. 
Published: July 2007

AbstractThe critical behaviour of the random field Ising model is calculated in d = 2 + ϵ dimensions, using previous findings on interface roughening of Grinstein and Ma. The critical exponents are expressed in terms of ϵ and the dimension β/v of the order parameter field. ϵ and β/v are assumed to be small. For nonvanishing random field strength HR the critical behaviour is governed by a zero temperature fixed point HRc ˜ (ϵ + 2β/v)3/4. In particular μ = 3/4 and v−1 = ⅔ (ϵ + 2β/v) are obtained for the interface tension and the correlation length exponent, respectively. The relation between interface and bulk correlation lengths in the various regions is discussed.
The Narrow Bands of Exciton Absorption in Polar Solids and Alloys
Authors: Kusmartsev F. V. 
Published: July 2007

AbstractAn analytical theory of the Urbach‐Martienssen tail for the Wannier‐Mott excitons in polar crystals and alloys is developed on the basis of the expansion of all quantities in the small parameter δ ≪ Ei(μ/M), where M and μ are the translation and the reduced masses of the exciton; Ei is the exciton Rydberg, and δ is the photon deficit. The exciton absorption coefficient and the length of the absorption tail are calculated. The latter characterizes the width of the exciton absorption band. The results obtained are compared with experiments on the exciton absorption in layered polar crystals.
Shake‐Effect in Radiative Auger Recombination of Carriers on Two‐Electron Impurity Centres in Semiconductors
Authors: Kovarskii V. A. , Chernysh L. V. , Sheinkman M. K. 
Published: July 2007

AbstractA calculation of the Auger‐capture cross‐section of a hole on two‐electron impurity centres is performed. For the first time in a semiconductor (and probably in solid state, in general) the “shake‐effect” accompanying this process is taken into account. Consideration of this effect gives the possibility of truthfull explanation of selection rules and magnitude of “two‐electron” luminescence in crystals.
Optical and Electrical Properties of Vanadium‐Doped GaAs
Authors: Ulrici W. , Friedland K. , Eaves L. , Halliday D. P. 
Published: July 2007

AbstractThe results of optical absorption, luminescence, and temperature‐dependent Hall‐effect measurements on GaAs: V, p‐type GaAs: V: Zn, and n‐type GaAs: V:Si grown by LEC‐technique are reported. It is found that the V ground state is located very close to or within the valence band and that the V acceptor level is at Ec − 0.14 eV. The near mid‐gap level in GaAs: V responsible for its semi‐insulating behaviour is proposed to be due to the complex (V‐ X), where the correlation between the photoionization absorption connected with this centre and the EL2 concentration suggests that X is an arsenic vacancy. From this level scheme conditions for growing GaAs: V which is semi‐insulating at room temperature are derived. The optical experiments on GaAs: V with different Fermi‐level positions confirm the assignment of the triple‐peaked absorption band at 1.1 eV to the 3A2 → 3T1(F) transition of V. The weak absorption due to the 3A2 → 3T2(F) transition is found at 0.79 eV. The analysis of the temperature dependence of the line shape of the → 3T1(F) absorption band as due to strong dynamical T ⊗ τ2 Jahn‐Teller effect provides the JT‐parameters EJT = 780 cm−1, hωτ = 75 cm−1, and c = 4.7 eV/nm. The temperature dependent asymmetry of the line shape is explained on the basis of earlier theoretical predictions of the simultaneous action of strong linear and quadratic JT‐coupling.
Transient Absorption of Xe and Kr Guest Atoms in Ar Crystals
Authors: Schröder T. , Dössel O. , Nahme H. , Schwentner N. 
Published: July 2007

AbstractTime resolved absorption spectra for transitions starting from the lowest excited electronic states of Kr(5s,3P2) and Xe(6s,3P2) guest atoms in Ar crystals show broad bands at 1.81 and 1.72 eV, respectively. The bands are assigned to ns → np multiplets of the guest atoms. The blue shift of 0.3 eV with respect to the gas phase and the large band width indicate a strong coupling of the transitions to the matrix. Transitions to higher states are not observed. The initial electronic states are metastable with lifetimes of 10−5s (Kr) and 3 × 10−6s (Xe).
The Spontaneous Resistivity Anisotropy of Iron‐Based Alloys
Authors: Muth P. , Christoph V. 
Published: July 2007

AbstractThe spontaneous resistivity anisotropy of Fe‐based alloys measured at low temperatures and the quotient of the residual sub‐band resistivities of the majority and minority spin‐band electrons are obviously strongly related. It can be shown that a theoretical expression derived for the spontaneous resistivity anisotropy of Ni‐based alloys represents the data of Fe‐based alloys, too. Other existing theoretical relations for the spontaneous resistivity anisotropy are analysed.
Acoustic Phenomena in Tunnel Junctions
Authors: Urushadze G. 
Published: July 2007

AbstractA change of the electron energy in a deformed crystal is described through strain potential tensor λik(p), its magnitude in real crystals still remaining obscure; no detailed calculations or systematic measurements in different metals have so far been attempted. Tunnel current (tc) response to an external sound field propagating parallel to the junction plane of a tunnel diode in the normal state is determined. Amplitudes of a sound‐induced high‐frequency t c with a nonzero potential difference at the junction are established, and the possibility of measuring metal strain potential in an electron tunelling experiment is discussed.
Solution of the Spin‐Hamiltonian with Orthorhombic HF and g‐Tensors (S = 1/2). I. Theory
Authors: Seth V. P. , Yadav A. , Bansal R. S. 
Published: July 2007

AbstractUsing perturbation methods a theory is developed to analyse the ESR spectra characterized by ℋ︁ = βH · g·S + S·A·I for S = 1/2. It is found that the perturbation is zero for isotropic g and A. For axially symmetric g and A, the perturbation term is zero when H is along z axis and for H along any other direction perturbation terms should be added which may be very small. For the general orientation of H an expression for the line position of the allowed transition is given.
Effect of Plastic Deformation upon Optical Absorption of KCl:Eu2+ Crystals
Authors: Czapelski M. , Suszyńska M. 
Published: July 2007

AbstractThe effect is studied of plastic deformation (by uniaxial compression) on the optical absorption spectrum of europium doped KCl crystals. The main effect of the stress applied is to decrease the value of the absorption coefficient characteristic of the high energy absorption band. The stress induced effect is quantitatively explained on the basis of elastic interactions between impurity–vacancy dipoles and edge dislocations moving in one pair of orthogonal slip planes.
Dynamic Conductivity Singularities of a Many‐Valley Semiconductor in a Quantizing Magnetic Field
Authors: Magarill L. I. , Savvinykh S. K. 
Published: July 2007

AbstractThe absorption of linear‐polarized electromagnetic waves in many‐valley n‐Ge type semiconductors in a quantizing magnetic field is considered. A low‐temperature region where the main scattering mechanism is the elastic collision of electrons on point defects is studied. Short‐range impurity centres (“isoelectronic ecntres”) are considered within a zero‐range potential model. The theory is developed for the case of low impurity concentration, and the absorption is expressed in terms of an one‐centre scattering operator. The parameters of the problem are intervalley and intravalley scattering lengths. Main attention is paid to the study of the frequency dependence of the absorption coefficient near resonance peaks due to transitions between Landau levels of different valleys and also due to those from localized impurity states to continuous spectrum. Formulae are derived to describe the shape of resonance peaks and their field and orientation dependences.
GMR Effect on Conversion Electron Polarization
Authors: Mitin A. V. , Popov E. A. 
Published: July 2007

Abstract(γ;e) conversion scattering under the GMR conditions is considered. To solve this problem the density matrix method is used. It is shown that the process is accompanied by the time oscillations of conversion electron (CE) flux. The oscillation frequencies are multiple to the frequency of rf magnetic field. CE polarization is analysed on the example 57Fe nuclei in iron. The possibility of application of these results for spin polarization study of the inner atomic shells is shown.
Displacement of the Fermi Level Due to Impurities in a Random Distribution
Authors: Yoshida K. 
Published: July 2007

AbstractThe displacement of the Fermi level, ΔEF, on alloying, when impurity atoms are in a random distribution, is investigated in terms of a cellular structure where spherical cells, each containing an impurity atom at its center, have various sizes. This model is a simple extension of Friedel's model in which all the cells have an equal size. An appropriate distribution function of cell sizes is estimated by the aid of a computer simulation. For a random distribution of impurity atoms, ΔEFp is found to depend more linearly on the impurity concentration than expected from Friedel's model. A comparison is made with experimental data reported in literature for copper alloys.
Electron Spin Resonance Study of Ni2+ Centers in AgCl(Cu, Ni)
Authors: van Robbroeck L. , Bouwen A. , Schoemaker D. 
Published: July 2007

AbstractSingle AgCl crystals doped with Cu2+ and Ni2+ were studied by means of electron spin resonance. As grown crystals contain three different Ni2+ centers which reduce to Ni+ defects under illumination at 50 K with blue light. Six Ni+ defects were found with tetragonal, orthorhombic, and cubic symmetry. At 101 K the orthorhombic centers transform to the tetragonal defects. The latter become thermally unstable at 135 K and induce the decay of the Cu2+ centers.
A Fast Computational Method to Obtain Spin‐Hamiltonian Parameters of S and I = 5/2 Ions
Authors: Korkmaz M. , Aktas B. 
Published: July 2007

AbstractWhen the crystal field term is not weak enough, the perturbation method is not convenient to obtain the ESR spin‐Hamiltonian parameters for ions with S > l/2. To overcome this difficulty the matrix diagonalization technique which is a rather lengthy and time consuming process, is generally used in the literature. A fast computational method is proposed based partly on diagonalization and partly on perturbation techniques to calculate these parameters quickly and accurately.
On the Theory of Scattering by Short‐Range Pointials
Authors: Iskra V. D. 
Published: July 2007

AbstractA convenient technique of handling δ‐like potentials is developed using a factorization device. Results are applied to study the temperature dependence of the mobility limited by scattering of the charge carriers by a set of randomly spaced centers with short‐range potentials. Born's approximation is avoided and resonance scattering is shown to be of some importance in a certain temperature range.
Photoconductivity of Corundum Irradiated with High Energy Electrons at Excitation of F and F+ Centres
Authors: Atabekyan R. R. , Vinetskii V. L. , Gevorkyan V. A. , Godenko L. P. , Ezoyan R. K. 
Published: July 2007

AbstractThe photoconductivity excited in the region of absorption of colour centres in irradiated corundum by high energy electrons is investigated. A theory of photoconductivity is constructed determined by electron jumps between spatially separated F+ centres. With reasonable values of parameters one may achieve a satisfactory quantitative agreement of theoretical and experimental values of the photocurrent.
Mössbauer radiation dynamical diffraction in crystals being subjected to the action of external variable fields
Authors: Baryshevskii V. G. , Skadorov V. V. 
Published: July 2007

AbstractA dynamical theory is developed of the Mossbauer radiation diffraction by crystals being subjected to an variable external field action. Equations describing the dynamical diffraction by nonstationary crystals are obtained. It is shown that the resonant interaction between Mössbauer radiation and shift field induced in the crystal by a variable external field giving rise to an effective conversion of the incident wave into a wave with changed frequency.
Band structure of TIGaSe2 ternary layered crystals
Authors: Abdullaeva S. G. , Mamedov N. T. 
Published: July 2007

AbstractThe band structure in the high‐symmetry points of the TIGaSe2, Brillouin zone is calculated by the pseudopotential method. The top of the valence band is found to be located at the Γ point. The bottom of the conduction band is located at the line Γ–Y and the additional extremum of this band – at the point Γ of the Brillouin zone of TlGaSe2. The data obtained are compared with the results of previous band calculations and optical absorption data of TlGaSe2.
Solution of the spin‐hamiltonian with orthorhombic HF and g‐tensors (S = 1/2). II. Application to VO2+ centres in oxide glasses
Authors: Seth V. P. , Yadav A. , Bansal R. S. 
Published: July 2007

AbstractA theory developed previously is used in the analysis of ESR spectra of VO2+ in ternary borate glasses. The theoretical optical basicity of these glasses is calculated. It is found that |P| and |A′‖| are larger and K is smaller in those glasses for which the optical basicity is large.
Photocarrier kinetics in IrBr‐doped AgBr
Authors: Spoonhower J. P. , Deri R. J. 
Published: July 2007

AbstractThe kinetics of photogenerated carriers in AgBr crystals doped with trivalent iridium are investigated by photoconductivity measurements. The temperature dependence of the photoelectron lifetime is highly dependent on the level of iridium doping. Experiments show that photoelectron‐iridium reaction cross‐sections have a weak dependence on the number of vacancies bound to the iridium site. Estimates of the cross sections for electron capture a t IrBr centers with one and two associated vacancies are deduced.
Low‐symmetry doped Cu(II) complexes in (gly)2CaCl2 · 4 H2O single crystal: EPR studies
Authors: Hoffmann S. K. , Goslar J. , Szczepaniak L. S. 
Published: July 2007

AbstractEPR results for copper(II) ions doped in (gly)2CaCl2 · 4H2O single crystals are reported. The copper(II) complex formed in the chromophore CuN2Cl4 displays rhombic crystal field symmetry with an unusual spin‐Hamiltonian parameter sequence: gx = 2.115, gy = 2.034, gz = 2.308, and Ax = 40.1, Ay = 113.4, Az = −73.0 × 10−4 cm−1. The g‐factors are related to the ground state wave function α |ad−bd〉 with α2 = 0.86, a = 0.9835, and b = 0.181, and the untypical hyperfine splitting parameters result from the very low value of the Fermi contact parameter of χ = 0.087.
Resonant excitation of helicon waves by two microwave beams in a solid state plasma
Authors: Maheshwari K. P. , Tarey G. 
Published: July 2007

AbstractAn investigation is made of resonant excitation of helicon waves at the difference frequency of two microwave beams propagating in a magneto‐active solid state plasma viz. n‐InSb. The two beams propagating obliquely with the magnetostatic field interact in the semiconductor to give rise to a nonlinear ponderomotive force at the difference frequency which resonantly excites helicon waves if the dispersion relation corresponding to helicon waves is satisfied. The results show that microwave beams of power densities 1 MW cm−2 can excite helicon waves of power density 0.98 kW cm−2 when ωc/ω = 25. The power carried by helicon waves depends on the direction of propagation of the pumps relative to magnetostatic field. For the parameters under consideration the power gets optimised at an angle θ = 63.4°. Helicon waves are not excited if the pumps propagate parallel or perpendicular to the magnetic field. The increase in magnetic field increases the power density of the excited helicon wave.
Nature of the centres of positron annihilation in intensively irradiated alkali halides
Authors: Annenkov Yu. M. , Nurmagambetov S. B. , Chormonov A. B. 
Published: July 2007

AbstractThe positron capture centres are identified in high irradiated (in the temperature range of 300 to 520 K) KBr. The dependences of the intensity of the annihilated 2γ radiation on the temperature of proton irradiation and that of a following pulse heating of crystals are studied. The spectra of optical absorption of the crystals are measured under identical conditions. The volume rates of a positron capture into the basic radiative defects are calculated. The divacancies are shown to be the basic centres of positron captnre in the investigated temperature range in the high irradiated alkali halides.
Magnetostatic interactions of moving vertical bloch lines in a domain wall
Authors: Kosiński R. A. , Strzeszewski J. 
Published: July 2007

AbstractThe propagation of a pair of vertical Bloch lines in a moving domain wall, used in a Bloch line memory, is simulated numerically using a full implicit method and taking into account non‐local magnetostatic interactions. Results concerning the influence of the magnetostatic interactions on the motion of vertical Bloch lines along the domain wall, in particular the process of their collision, are discussed.
Nature of deep luminescence centres in CdSe and CdSexTe1–x
Authors: Ermolovich I. B. , Milenin V. V. 
Published: July 2007

AbstractBoth, the dependences of the luminescence intensities of the bands with λm = 920 and 1160nm at 77 K in CdSe and the corresponding bands in CdSexTe1–x (x = 0 to 1) on temperature and the dependences of band intensities on excitation level measured at low temperatures and at the temperatures from the ranges of band quenching are investigated. Obtained data enable conclusion to be made about both band quenching mechanisms: the “external” mechanism is valid for the 920 nm bands and the “internal” one is valid for the 1160nm bands. The parameters of electron‐phonon interactions at radiative carrier capture on investigated centres are obtained and the configuration coordinate models for both types of centres are constructed. Different mechanisms are shown to be caused by the differences of chemical nature and geometrical configuration of the 920 and 1160 nm centres. It is shown also that the process of the nearest anion altering of the emission centre causes the change of its interaction with lattice.
Twofold coordinated Si and Ge atoms and “hydrogen” paramagnetic centers in amorphous SiO2 and GeO2
Authors: Radtsig V. A. , Bobyshev A. A. 
Published: July 2007

AbstractA new type of intrinsic structure defects in amorphous SiO, and GeO, – twofold coordinated silicon magnified image and germanium magnified image – is identified. In the reaction with H(D)atoms they convert to paramagnetic centers magnified image. The electron structure, geometry, and chemical properties of these centers are analyzed.
The origin of the minority impurity states in heavily doped semiconductors
Authors: Domanevskii D. S. , Krasovskii V. V. , Prokopenya M. V. , Vilkotskii V. A. , Zhokhovets S. V. 
Published: July 2007

AbstractThe influence is examined of growth conditions of heavily doped n‐type semiconductors on the width and energy position of Gaussian‐shape impurity band where non‐equilibrium holes are localized. The energy levels of the impurity band are shown to be caused by associations of oppositely charged crystal imperfections (so‐called associates) including several shallow donor impurity atoms and a deep structural defect. The reason of Gaussian broadening of these states is a random spatial arrangement of associated imperfections about each other within a given associate.
Lattice dynamics and ionic conductivity of PbF2:6%LiF superionic crystals
Authors: Kosacki I. , Hibner K. , Litvinchuk A. P. , Valakh M. Ya. 
Published: July 2007

AbstractTemperature studies of lattice dynamics and ionic conductivity, within the temperature range of 100 to 700 K, are performed for PbF2 and PbF2:6% LiF superionic crystals. The doped crystals exhibit a decreased activation energy of the conductivity. A decrease, by about 70 degrees, in the temperature at which the ionic conductivity changes and Raman spectra anomalies occur is observed. It is found that at temperatures significantly lower than that of the superionic state transition, the Raman line form is determined by processes of phonon scattering at thermally excited defects.
The effects of electron excitation energy transfer to the impurity centre in LiH crystals
Authors: Cholakh S. O. , Pustovarov V. A. , Shulgin B. V. 
Published: July 2007

AbstractPossible mechanisms of electron excitation energy transfer to the impurity centres in LiH crystals are considered in the case of LiH :Mg and LiH :Na crystals. Along with the electron‐hole mechanism, the exciton mechanism of energy transfer is of considerable efficiency. The main role in this process belongs to unrelaxed excitons. The free path value of excitons in LiH is estimated to be about 3 × 103 nm at 4.2 K. Optical manifestation of energy transfer is observed both, in the impurity centre luminescence and in the formation of Frenkel radiation defects as a result of nonradiative decay of near‐impurity excitons.
The lorenz number of some AgCr alloys
Authors: Ducastel R. , Pitsi G. 
Published: July 2007

AbstractThe temperature dependence of the Lorenz number L of five coldworked AgCr Kondo alloys is measured between 1.5 and 14 K by combining the results of thermal and electrical conductivity measurements. The results are compared with data obtained on other Kondo systems. Inelastic electron‐dislocation scattering is proposed for explaining the value of L (T → 0) lower than the classical Sommerfeld value L0.
Non‐linear conduction in networks of random potential barriers
Authors: Fishchuk I. I. 
Published: July 2007

AbstractThe dc conductivity in high electrical fields for the cubic network of the random macroscopic barriers with non‐linear I–U characteristics is calculated. For not a very large spread of the heights of the potential barriers the differential conductivity decreases with increasing electrical field just after Ohmic region. This result is obtained using both, the effective medium and the cumulant approximations. In the ohmic region the cumulant approximation result for the dependence of the conductivity on the degree of barriers height spreading is in better agreement with computer results than the effective medium approximation result.