bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hopping Electrical Conduction and Thermal Breakdown in Natural and Synthetic Mica
Authors: Davidson A. T. , Yoffe A. D. 
Published: July 2007

AbstractThe electrical properties of thin mica crystals have been measured between 4 and 520°K, and have been related to optical absorption measurements and to electron microscope observations. The dc conductivity and breakdown strength depends on the concentration of iron and titanium in the mica. It is suggested that impurities act as localized centres for electrical conduction in mica and that the Poole‐Frenkel model applies at high temperatures while electrons tunnel between the centres at low temperatures. The conductivity of mica depends on the frequency of the applied field. Two types of breakdown have been found. The results are interpreted as avalanche breakdown in synthetic micas and thermal breakdown in natural micas.
Experimental Evidence for Interband Mixing in Rare‐Earth Intermetallic Compounds
Authors: de Wijn H. W. , Buschow K. H. J. , van Diepen A. M. 
Published: July 2007

AbstractMeasurements of the Knight shifts and susceptibilities of rare‐earth intermetallic compounds have been extended to YCu, GdCu, TbCu, DyCu, HoCu, and ErCu. The phenomenological exchange constants 𝒥sf between 4f‐electron spins and conduction‐electron spins are derived to be −0.21 eV. Also the paramagnetic Curie temperatures of the compounds GdCu1−xGax have been measured. The Knight shifts and Curie temperatures are discussed in terms of the Ruderman‐Kittel‐Kasuya‐Yosida theory. For the various series of rare‐earth intermetallic compounds the s‐f exchange integral Γ = 2 J(0) and the Fermi wave vector kF have been determined. Γ is found to be a continuous function of kF, with a sign reversal at kF ≈ 1.4 Å−1. This observed behavior is consistent with the calculations of Watson, Koide, Peter, and Freeman on the effect of interband mixing on the exchange interactions.
Plasma Oscillations in Semiconductors with Non‐Standard Dispersion Law in the Presence of Electric and Magnetic Fields
Authors: Almasov L. A. , Dykman I. M. 
Published: July 2007

AbstractThe effect of the magnetic field H on the frequency of plasma oscillations in semiconductors with non‐standard energy band structure is investigated. In such semiconductors in the presence of a constant electric field F a specific bandstructural mechanism of amplification or attenuation of the oscillations arises. Assuming isotropic energy band structure of Kane type, this mechanism leads to attenuation. The magnetic field H ⟂ F decreases the attenuation, while the oscillations polarized in a certain way can even amplify it. Assuming a weakly anisotropic band structure, like that of the holes in Ge, the magnetic field affects the oscillations of light and heavy holes in different way. In this case also polarization directions are possible at which the bandstructural amplification of oscillation occurs in the magnetic field.
Green Function Theory of Transport Properties of Anharmonic Metals
Authors: Kishore R. 
Published: July 2007

AbstractGeneral expressions for the electron and phonon energy shift and widths are derived with the help of the double time temperature dependent Green's function by using a Hamiltonian which includes both anharmonicity and electron‐phonon interaction. The expression for the phonon width shows that Green's function technique provides an understanding of Matthiessen's rule. Well known temperature dependence of the electron and the phonon relaxation times is reproduced by a simple calculation of the electron and the phonon widths at low and high temperature limits. It is found that the effect of anharmonicity on the electronic transport properties of metals is negligible. Its effect on the lattice transport properties is predominant at high temperature and at low temperature the effect of electron‐phonon interaction is predominant.
Spin‐Wave Theory of the Anisotropic Ferromagnetic
Authors: Mitsek A. I. , Kolmakova N. P. , Skryabin Yu. N. 
Published: July 2007

AbstractUsing the method of successive approximations, the spin‐wave theory of the anisotropic ferromagnetic is constructed in the Heisenberg model. The influence of the magnetic anisotropy on the specific heat, the temperature dependence of the spontaneous magnetization and the paramagnetic susceptibility as well as the temperature dependence of the magnetic anisotropy constant K1 is calculated. The difference in the temperature dependences of the “single‐ion” anisotropy and “anisotropic exchange” is discussed. It is shown that when K1 is small enough, the frequency of the ferromagnetic resonance (FMR) depends on T in the same way, as in the thermodynamic theory of FMR. The line‐width of FMR ΔH is determined by 3‐magnon processes and depends weakly on temperature. The processes of the transformation of a quantum of uniform precession into two spin waves of different polarizations gives the main contribution to ΔH. The contribution of 2‐magnon processes of the scattering on the impurity atoms is calculated as well.
Atomistische Behandlung von Kinke und Sprung einer Stufenversetzung in NaCl. II. Der abrupte Sprung
Authors: Eisenblätter J. 
Published: July 2007

AbstractNach denselben Methoden wie in Teil I dieser Arbeit [1] werden Energien der zwei niedrigsten abrupten Sprünge und Energien der Dissoziation eines vollen in zwei Halbsprünge berechnet.
OH− Dissociation and U2 Decomposition in Hydroxide‐Doped KCl and KBr Crystals
Authors: Kurz G. 
Published: July 2007

AbstractWe report quantitative results concerning the dissociation of OH−, supporting the conception given first by Kerkhoff. U2 centres created by this reaction are thermally stable below about 100°K. It is shown that U2 centres can be destroyed by optical bleaching. At 4.5°K, U and H centres are created simultaneously; this is described as

We suggest for the underlying mechanism that the first process after U2 excitation is a noncubic relaxation of the lattice (static Jahn‐Teller effect) followed by a 〈110〉 replacement sequence as described by Williams to form a H‐centre–vacancy pair, the vacancy finally being occupied by the H− ion. – In KCl a reverse reaction can be induced either by thermal activation or by bleaching with H light. – Oscillator strengths of the U2, H, and OH− bands are calculated from the results using the Smakula equation.
De Haas ‐ Van Alphen and Shubnikov ‐ De Haas Effect in n‐HgSe in Strong Magnetic Fields
Authors: Bliek L. M. , Landwehr G. 
Published: July 2007

AbstractThe De Haas ‐ Van Alphen and the Shubnikov ‐ De Haas effect are measured on oriented samples of single‐crystalline HgSe with electron concentrations between 1.08 and 3.26 × 1018 cm−3 in pulsed magnetic fields up to 210 kOe. The results in strong fields show that the beating of the oscillations observed at smaller fields is due to inversion asymmetry splitting rather than to anisotropy of the Fermi surface. A pronounced spin splitting of about 1/4 of a period is observed, allowing the evaluation of the Landé factor of the conduction electrons.
Anisotropy of the Electric Conductivity of Tellurium Single Crystals
Authors: Rothkirch L. , Link R. , Sauer W. , Manglus F. 
Published: July 2007

AbstractThe quantity σ⟂/σ∥ of tellurium single crystals is measured in the temperature range 80 to 550°K. The results may be understood under following assumptions: The relaxation time for the scattering of holes by acoustic phonons is nearly isotropic; the relaxation time for the scattering of holes by dislocations is characterized by the relation 〈τp⟂〉 < 〈τp∥〉; the anisotropy of the effective hole mass mp∥/mp⟂ is markedly temperature‐dependent; the highest valence band edge and the lowest conduction band edge show approximately the same anisotropy between 200 and 550°K.
The Effect of the Local Mode Self‐Energy in the U‐Center Sidebands
Authors: Zeyher R. , Bilz H. 
Published: July 2007

AbstractThe theory of the sideband absorption of the U‐center is reformulated. The contribution of the anharmonic self‐energy of the local mode is taken into account in the resonance denominator and in the sideband absorption itself. The first modification explains some difficulties in describing peak positions and heights arising in the usual perturbation treatment. The second effect is a simple form of final state interaction which leads to an absorption in the gap region of the sideband. Numerical values of the effects are given.
A Study of the Effect of Deformation on the ESR, Luminescence, and Absorption of MgO Single Crystals
Authors: Sibley W. A. , Kolopus J. L. , Mallard W. C. 
Published: July 2007

AbstractThe effect of plastic deformation on the optical absorption, ESR, and thermoluminescent properties of MgO has been investigated. Plastic deformation produces an optical absorption band at about 217 nm whose intensity is proportional to the percent of deformation. No new ESR signals were detected in the deformed crystals. When deformed crystals are irradiated with 60CO γ‐rays, however, the ESR signal from the F‐center is observed and several new optical absorption bands also appear. Impurity ion ESR signals in γ‐irradiated samples have been compared with thermoluminescence spectra. The results indicate that the blue thermoluminescence at 3.3 eV and 85°C is due to Fe2+ converting to Fe3+ and the red thermoluminescence at 1.7 eV and 85°C is due to the formation of Cr3+.
Calculation of the Influence of Bound Divacancies on the Isotope Effect for Self‐Diffusion in F.C.C. Metals
Authors: Bakker H. 
Published: July 2007

AbstractWith the aid of Howard's theory for computing the correlation factor for self‐diffusion by divacancies, the influence of divacancies on the isotope effect for self‐diffusion in f.c.c. metals is calculated. It turns out that a divacancy contribution lowers the isotope effect. This result is compared with experimental values for palladium and silver, and with the usual interpretation of small isotope effects following Vineyard's theory.
Density Matrix Method in the Theory of Optical Spectra of Impurities in Solids
Authors: Peuker K. 
Published: July 2007

AbstractThe results of a previous paper describing the vibrational structure in the secondary radiation spectrum of impurities in solids are extended to the general case of finite temperature. The impurity centres are treated as two‐level electronic systems interacting with a localized mode of vibration. The anharmonic interaction of the localized mode with the crystal modes is taken into account. Expressions are derived describing the Raman‐type and luminescence parts of the spectrum. The relation between the integral intensities of these spectral components are examined as a function of the frequency of the incident light.
Electron Drift Mobility in KCl
Authors: Hirth H. , Tödheide‐Haupt U. 
Published: July 2007

AbstractFrom electron transit time measurements the electron drift mobility in KCl has been deduced for the temperature range 200 to 500 °K. By comparison with low temperature Hall mobility data it is concluded that above 300 °K the measured values coincide with the microscopic mobility μ of conduction band electrons which may be described by μ = μ0[exp (θ/T) − 1]. Below 300 °K the measured drift mobility is controlled by the interaction of the conduction band electrons with shallow traps. These traps also influence the electron lifetime. Since the electron mobilities in AgCl and TlCl deduced from the literature may also be represented by the expression given above that this expression is generally valid for ionic crystals with intermediate electron‐phonon coupling.
Thermal Conductivity of GeS and GeSe
Authors: Okhotin A. S. , Krestovnikov A. N. , Aivazov A. A. , Pushkarskii A. S. 
Published: July 2007

AbstractThe thermal conductivity of the semiconductor compounds GeS and GeSe has been measured in an argon atmosphere in the range from room temperature to 500 °C. The analysis of the data obtained indicates that the heat transfer in these compounds is governed by phonons. The applicability of Keyes' formula to the description of the high‐temperature thermal conductivity of germanium chalcogenides is demonstrated.
The Electronic Polarizabilities of Ions in Alkali Halide Crystals
Authors: Ledovskaya E. M. 
Published: July 2007

AbstractAn expression for the electronic polarizability of ions in ideal alkali halides is obtained. For this purpose a second order correction of the perturbation theory to the energy of the crystal, placed in an external electric field, is used. As a perturbation the interaction of ions in the crystal and the interaction of the crystal with the external macroscopic electric field are taken simultaneously. The additivity rule for the electronic polarizability of the ideal crystal and for the polarization energy of the non‐ideal crystal is confirmed. The difference between the value of the electronic polarizability of the ion in a crystal and that of the free ion is qualitatively correct.
On the Long Period Photoconductivity of Cu2O
Authors: Surnev L. 
Published: July 2007

AbstractThe slow photoconductivity of Cu2O has been studied. The results obtained can be explained by assuming the existence of three types of traps. The first type contains the highest levels in the forbidden gap. They create the fast component (τ ≈ 10−4 s) of the photoconductivity at room temperature. Levels lying 0.7 eV below the bottom of the conduction band correspond to the second type of traps. They cause a reversible slow component at temperatures below 130 °C. The traps associated with the deepest levels (1.35 eV) produce an irreversible slow component of the photoconductivity at temperatures below 120 °C. The close correlation between the photoconductivity components leads to the assumption that all three types of traps are concentrated on definite sites of the sample. For that reason, with the filling up of traps, barriers are formed in the vicinity of these sites. These barriers determine the kinetics and extent of filling of the traps.
On the Angular Variation and Texture Dependence of Young's Modulus in Cold‐Rolled Copper Sheet
Authors: Bunge H. J. , Ebert R. , Günther F. 
Published: July 2007

AbstractThe Young's modulus was measured in different directions in the rolling plane of coldrolled copper sheets with different textures, and also calculated in the Hill approximation from X‐ray data. The agreement was fairly good. A deviation of about 7% with twofold symmetry with respect to the normal direction is possibly due to the form of the grains or the orientation correlation.
Investigation of the Energy Band Structure of GaSb by a Semi‐Empirical Kohn‐Rostoker Method
Authors: Bordure G. 
Published: July 2007

AbstractThe energy band structure of GaSb is investigated by the Kohn‐Rostoker (KR) method. A “muffin‐tin” potential is described and two parameters are introduced for fitting some splittings at points of symmetry of the Brillouin zone with experimental data. Other characteristic splittings are compared with experimental results. The results are also compared with those obtained by other methods.
ENDOR Measurements of Interstitial Hydrogen Atoms in RbCl (U2 Centres)
Authors: Lehnert G. , Spaeth J. M. 
Published: July 2007

AbstractAn ENDOR investigation of U2 centres in RbCl is reported. The superhyperfine and quadrupole constants of two Rb shells and one Cl shell in the surrounding lattice are determined. The experimental results are compared with those obtained in other alkali halides. The measurements are interpreted in terms of a simple U2 centre wave function.
Über die Energie‐ und die Energie‐Winkel‐Verteilung der Anregung von Rumpfelektronen durch Stoß mit schnellen Primärelektronen bei Natrium
Authors: Arendt P. 
Published: July 2007

AbstractDie in [2] angegebene Anregungsfunktion aus Rumpfbändern beim Stoß mit schnellen Primärelektronen wird am Beispiel des Natriums berechnet. Es ergibt sich, daß die Anregung aus den Rumpfbändern bedeutend weniger anisotrop erfolgt als die Anregung aus dem Leitungsband. Die anhand der berechneten Verteilung mit Hilfe einer Transporttheorie berechnete Sekundärausbeute stimmt im Rahmen der zu erwartenden Genauigkeit mit der experimentellen Ausbeute überein.
Diffraction Contrast from Dauphiné Twin Boundaries in Quartz
Authors: McLaren A. C. , Phakey P. P. 
Published: July 2007

AbstractElectron diffraction contrast evidence is obtained for the presence of Dauphiné twins in amethyst quartz. A model for the Dauphiné twin boundary which does not involve broken SiO bonds is proposed and shown to be consistent with the contrast features observed with different operating reflection. X‐ray diffraction topography of macroscopic Dauphiné twin boundaries in natural quartz show identical contrast effects and support the electron microscope observations. – It is shown that a different type of fringe pattern, not previously described, can arise at boundaries if the extinction distances in the two parts of the twin differ significantly. Diffraction contrast from such fringe patterns is described and explained using Gevers‐Amelinckx intensity relations.
Electron Microscopic Contrast Effects at the Interface between Two Different Polytypes. II. Interface 2H–4H
Authors: d'Aragona F. Secco , Delavignette P. , Gevers R. , Amelinckx S. 
Published: July 2007

AbstractThe contrast effects associated with the interface between two different polytypes of zinc sulfide, 2H and 4H are discussed. A special type of fringes characterized by a different spacing at the top and bottom end is associated with such interfaces. The fringe patterns associated with overlapping interfaces are discussed as well. The transformation 2H–4H is found to be a shear transformation. The prismatic stacking faults in wurtzite are found to be growth faults; they are eliminated by the passage of transformation partials on the basal plane.
The Nucleation of Stripe Domains in Thin Ferromagnetic Films
Authors: Holz A. , Kronmüller H. 
Published: July 2007

AbstractA micromagnetic calculation is given of the critical thickness of the nucleation of stripe domains in thin ferromagnetic films with so‐called perpendicular anisotropy. The micromagnetic equations were solved in linear approximation by means of a complete system of functions. The paper presents the critical thickness Dcr and the corresponding wavelength λcr as a function of the ferromagnetic constants. The agreement between our calculations and the measurements of Saito et al. on permalloy is good. For Fe‐films good agreement with the measurements of Bourret and Dautreppe is obtained only for Dcr but not for λcr. The calculated value for λcr is about a factor 1.5 greater than the experimental value.
Recombination Radiation Spectra in ZnSiP2 Crystals
Authors: Alekperova E. E. , Valov Yu. A. , Goryunova N. A. , Ryvkin S. M. , Shpenkov G. P. 
Published: July 2007

AbstractThe recombination radiation spectra of ZnSiP2 single crystals produced by different methods and doped with different impurities have been measured. The recombination radiation was excited by a high‐energy electron beam. The recombination radiation spectra of ZnSiP2 appeared to be similar to that of the wide forbidden band A3B5 phosphides. The recombination takes place at levels located in the forbidden band of this semiconductor. The investigation of the recombination radiation spectra permits us to judge of luminescent properties of ZnSiP2 crystals produced by different techniques and of their energetic spectrum. In some cases it gives a possibility to some extent to characterize the peculiarities of methods of production of this substance.
Spectral Characteristics of the Injection Quantum‐Amplifier
Authors: Oraevskii I. N. , Popov Yu. M. , Strakhovskii G. M. 
Published: July 2007

AbstractExperimental investigations and a theoretical analysis were made of the spectral characteristics of an injection quantum‐amplifier based on GaAs diodes. The feedback in a Fabry‐Perot cavity was attenuated by using an antireflective coating. For a sample whose characteristics were investigated in detail the threshold current after the coating was 7.8 times higher. That permitted to amplify a signal by a factor 103 without noticeable regeneration. For sufficiently small input signals the gain dependences on frequency and pumping current were measured when the amplifier operated in a linear regime. The results are discussed in terms of energy states (“tails”) formed near the conduction band by the impurities. Possible reasons of the discrepancy between the theoretical and experimental results at high frequencies and high currents are discussed.
Generation of the Exciton‐Impurity Complex by Fast Electrons
Authors: Glauberman A. E. , Pundik A. V. , Kozitskii S. V. , Ruvinskii M. A. 
Published: July 2007

AbstractThe problem of excitation of the exciton‐impurity complex (EIC) by fast electrons in a non‐metallic crystal is considered using a many‐electron approach. The operators which describe singlet and triplet state of EIC are introduced. The expressions for the probability of creation of the EIC are obtained and possible selection rules for corresponding transitions are analysed. A comparison is made with case of generation of free Wannier‐Mott exciton.
Anregungsspektren stationärer Photoströme in Anthrazen‐Kristallen im Bereich der Singulett‐Absorption
Authors: Bauser H. , Ruf H. H. 
Published: July 2007

AbstractIm Bereich der Singulett‐Absorption verläuft das Photostromspektrum nicht immer im gleichen Sinn wie das Absorptionsspektrum, sondern oft im Gegensinn; ferner tritt ein vorgelagertes Maximum bei 415 bis 430 nm auf. Der Typus des Photostromspektrums wird bestimmt durch die Reinheit der Kristalle, die Injektionsfähigkeit der Anode, die angelegte Spannung und die Bestrahlungsstärke. Der qualitativen Deutung der Meßergebnisse werden Trägererzeugung an der Oberfläche durch Singulettexzitonen und Trägerbefreiung im Inneren durch Triplettexzitonen als konkurrierende Prozesse zugrunde gelegt. — Die Lage des vorgelagerten Maximums läßt sich unter Berücksichtigung der inhomogenen Lichtverteilung im Kristall berechnen. Im Gebiet starker Absorption überwiegt die Trägerbefreiung durch Triplettexzitonen, die durch reabsorbiertes Fluoreszenzlicht erzeugt werden.
Mössbauer Investigation of Ferroelectric Boracites
Authors: Trooster J. M. 
Published: July 2007

AbstractThe Mössbauer spectra of 57Fe in the iron‐boracites Fe3B7O13X with X = Cl, Br, or I, and of 57Fe as an impurity in Ni3B7O13X have been measured at temperatures between 80 and 1100 °K. The results give qualitative information on the vibration amplitude in the different phases, on the crystal field splitting of the Fe2+ ion in the cubic phase, and on the character of the binding of the Fe2+ ion, and have led to the discovery of a trigonal phase in the Fe boracites.
Electrical Resistivity of Noble Metals by Krebs's Method
Authors: Singh A. K. , Sharma P. K. 
Published: July 2007

AbstractThe electrical resistivity of the noble metals copper, silver, and gold as a function of temperature is calculated in the free‐electron approximation using Krebs's model for the lattice dynamics of metals. Bailyn's averaging procedure is used to simplify formidable integrals over the Fermi surface. The calculated values of the resistivity are compared with available experimental data. The general shape of the theoretical and experimental resistivity curve is found to be similar, but the experimental values exceed the theoretical ones.
Cyclotron Masses and Orbital Diameters in Ag Determined by Cyclotron Resonance in a Thin Slab
Authors: Henningsen J. O. 
Published: July 2007

AbstractThe cyclotron mass of neck orbits in Ag has been determined by performing the experiments on a thin slab. This geometry allows one to eliminate the belly orbits. The result mc/m0 = 0.37 ± 0.01 differs from previous cyclotron resonance measurements, but is in agreement with the theory and de Haas‐van Alphen experiments. In addition approximate k‐space diameters have been determined for the central and non‐central [111] belly orbits. In both cases the agreement with theory is good.