bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Copper Layers on the Coercive Force of Permalloy Films
Authors: Grishechkin M. I. , Telesnin R. V. , Durasova Yu. A. , Osukhovskii V. E. 
Published: July 2007

AbstractThree mechanism of the effect of a copper layer on the coercive force of films are studied in this work: variation in the “roughness” of the substrate; diffusion of the copper into the permalloy; variation in the energy of exchange interaction between permalloy films separated by a copper layer. It is found, that an increment of the coercive force (ΔHc) with time is directly proportional to the effective diffusion depth, Δd. The results of experimental investigations on the condensation of metallic film make it possible to single out the following stages of this process: the formation of stable nuclei, the coalescence of discrete nuclei to a continuous layer; the growth of crystallites with a further increase of the thickness of continuous films. Observation of structures of interlayers under an electron microscope indicates that in wide ranges of thickness and deposition temperatures the interlayer consists of individual stable nuclei. The presence of exchange interaction between separated magnetic layers due to their direct contact makes it possible to explain the experimental results.
The Overshoot Phenomena in Single Crystals of Cu‐15 at% Al Tested in Tension. II. Orientation and Temperature Dependence of the Overshoot
Authors: Tisone T. C. , Brittain J. O. , Meshii M. 
Published: July 2007

AbstractOvershooting in Cu‐15 at% Al single crystals was studied as a function of quenching temperature, testing temperature, and initial tensile axis orientation. Overshooting was found to be independent of orientation and test temperature but the degree of overshoot appeared to increase with increasing quench temperature. It was concluded that the overshoot was not a direct function of the stacking fault energy in the range of 5 to 10 erg/cm2 for a Cu‐15 at% Al alloy. A model for overshoot was developed based on the collapse of Lomer‐Cottrell dislocations under the line tension of bowed out conjugate dislocation segments.
Electrical Properties of Dislocations in Ge and Si
Authors: Schröter W. , Labusch R. 
Published: July 2007

AbstractThe occupation statistics of the energy levels which are introduced by dislocations in Ge and Si are carried out taking into account that charged dislocations are a strong perturbation for the energy levels of the valence and the conduction band. The result is a theoretical relation between the line charge of the dislocation and the apparent experimental Fermi energy which is obtained from the number of free carriers. Comparing this relation with Hall effect measurements the position of the neutral dislocation level in the energy gap and the dislocation length per unit volume that is electrically active can be determined. Possible mechanisms for the screening of charged dislocations are discussed. It turns out that former screening models are appropriate only at very low temperatures and that for a wide range of experimental conditions the screening is done by a rearrangement of free carriers.
Thermodynamic Calculations of the Debye‐Waller Frequency Integrals of Alkaline Earth Fluorides
Authors: Brade R. M. , Yates B. 
Published: July 2007

AbstractThe maximum frequencies of the Debye distributions having the same n‐th moments as the vibrational frequency spectra in CaF2, SrF2, and BaF2, calculated from specific heat, thermal expansion, and elastic constant data, have been applied in the quasi‐harmonic approximation to calculate the Debye‐Waller frequency integrals of these solids. High‐and low‐temperature series expansions and Padé approximants have been employed to calculate these parameters as functions of temperature between 0 and 300 °K. Good agreement is observed between the values calculated for CaF2 and BaF2 at room temperature and those based upon neutron diffraction studies.
A. Semi‐Empirical Model for the Valence Band Structure of Tellurium
Authors: Betbeder‐Matibet O. , Hulin M. 
Published: July 2007

AbstractA simple model for the valence band structure of tellurium, in the neighbourhood of its maximum, has been derived. It takes account of spin‐orbit coupling and depends upon a restricted set of parameters which can all be determined from experimental data. Most of the qualitative features of electronic properties (Shubnikov‐de Haas effect, cyclotron resonance, and optical absorption) can be explained by this model, and a quantitative agreement between theory and experiments can be obtained.
Dichroïsme linéaire sous contrainte des matrices cubiques dopées
Authors: Duran J. 
Published: July 2007

AbstractOn envisage l'extension de l'étude des effets piézospectroscopiques aux raies d'absorption larges. On analyse les différents facteurs intervenant dans le dichroïsme linéaire sous contrainte des matrices cubiques contenant des centres possédant la dégénérescence d'orientation et (ou) électronique. On démontre et on vérifie expérimentalement des relations valables dans tous les types de centres entre les dichroïsmes mesurés pour différentes directions de pression et d'observation parallèles aux axes d'ordre 2, 3 et 4 du cube. On donne un tableau général des dichroïsmes linéaires calculés pour tous les types de centres anisotropes susceptibles d'exister dans les matrices cubiques. Enfin l'examen des effets de la température et des mélanges des fonctions d'onde par la pression permet de donner une formulation générale du dichroïsme linéaire sous contrainte analogue à celle du dichroïsme circulaire magnétique.
Mössbauer Effect for Fe57 in CoCl2 and CoF2
Authors: Cavanagh J. F. 
Published: July 2007

AbstractThe Mössbauer effect for Fe57 in CoCl2 and CoF2 has been measured by using them as sources in a resonant absorption experiment. While the CoCl2 spectra indicate only a 2+ charge state for the Fe57 ion, the CoF2 spectra indicate both a 3+ and a 2+ charge state. When a sample of CoF2 is used as an absorber doped with a small amount of iron enriched in Fe57, however, only 2+ charge state lines appear in the absorption spectra. This is interpreted as resulting from a local environment change associated with Auger aftereffects following K‐capture. The internal magnetic field has been estimated for each compound below its Néel temperature. Values of (49 ± 2) kOe for CoCl2 and (245 ± 2) kOe for CoF2 were found at 10 and 11 °K, respectively, for the field at an Fe2+ nucleus.
Temperature Distribution and Its Kinetics in a Semiconducting Sandwich
Authors: Böer K. W. , Döhler G. 
Published: July 2007

AbstractThe temperature distribution and its change in time is calculated for a semiconducting sandwich between two metal electrodes by solving the thermal balance equation including Joule's heating for one spatial coordinate and neglecting space‐charge effects. As boundary conditions, three cases are analysed: perfect cooling and Newton's cooling of the metal electrodes, however neglecting a temperature drop in the metal layers, or including a finite heat conductivity of the electrodes.
The Dependence of Cd Diffusion and Electrical Conductivity in CdS on Cd Partial Pressure and Temperature
Authors: Shaw D. , Whelan R. C. 
Published: July 2007

AbstractThe diffusion coefficient of Cd in undoped single crystal CdS has been measured at 850 °C as a function of Cd pressure, pCd, by a radiotracer method. The electrical conductivity of similar CdS samples has also been measured as a function of pCd in the temperature range 660 to 950 °C. It is concluded that the defects V″Cd and Cd are responsible for Cd diffusion at 850 °C and that a satisfactory account of the results can be given in terms of Cd interstitials and vacancies plus a residual shallow foreign donor. A model for the defect structure in CdS at 850 °C is presented in terms of Cd vacancies and interstitials.
Exciton Diffusion and Multimode Behaviour in Electron‐Beam‐Pumped CdS Lasers
Authors: Bille J. 
Published: July 2007

AbstractFrom CdS platelet crystals coherent radiation can be obtained resulting from the decay of free excitons to photons and longitudinal optical phonons (line ALO). In semiconductor lasers as CdS with a homogeneously broadened spontaneous emission line spatial inhomogeneity of the inverted population can lead to multimode oscillation. The number of axial modes oscillating simultaneously for a given excitation value above the threshold depends on the diffusion velocity of the inverted carriers, whereby the diffusion is smoothing out the spatial inhomogeneities. The fitting of the experimental data by the theory of Statz and Tang enables us to determine the exciton diffusion length at liquid‐air temperature; we find LDiff = 0.1 μm.
A Calculation of the Formation and Migration Entropies of Surface Defects in Copper
Authors: Wynblatt P. 
Published: July 2007

AbstractFormation entropies, frequency factors, and associated migration entropies have been calculated on copper surfaces of (100), (110), and (111) orientations for both terrace vacancies and adatoms, using a discrete vibrational approach. The vibrational spectra for the various defect configurations have been obtained using a quasi‐harmonic Einstein model in conjunction with a modified Morse function force law. ‐ The calculated quantities have been used to estimate Arrhenius D0's for intrinsic, single‐defect‐controlled diffusion. When these quantities are taken together with previously calculated activation energies for surface self‐diffusion, it is possible to obtain theoretical Arrhenius plots for each defect on a given surface orientation. The results are also helpful in the evaluation of earlier mechanistic interpretations of the observed curvature in the experimental Arrhenius plots.
The Infrared Absorption of the FCl− Heteronuclear Molecule Ion in KCl
Authors: Susman S. 
Published: July 2007

AbstractSingle crystals of KCl doped with KF and exposed to high dosages of Co60 γ‐radiation develop a simple doublet absorption on the high frequency edge of the KCl reststrahl. This 403.7—399.8 cm−1 doublet is assigned to the fundamental internal vibration of the FCl− heteronuclear molecule ion. The doublet separation, intensity ratio, thermal decay, optical bleaching and polarization properties support this assignment. The internal stretching frequency of FCl− in KCl is not markedly different than would be approximated from gas phase data for the neutral species.
Electron Metallography of a Non‐Classical Order—Disorder Transition
Authors: Swann P. R. , Duff W. R. , Fisher R. M. 
Published: July 2007

AbstractTransmission electron metallography has been used to resolve the microstructural changes which occur during the D03⇄L20 transition in an Fe26.5at%Al alloy. The micrographs show evidence for a) long‐range‐order fluctuations near the critical temperature, b) local lowering of a critical temperature in the neighborhood of domain boundaries, and c) absence of a stable two‐phase field separating the D03 and L20 phases. From these results it is concluded that the subject transition is not a classical (nucleation and growth) phase change.
Magnetic Anisotropy in F.C.C. Single Crystal Cobalt—Nickel Electrodeposited Films. I. Magnetocrystalline Anisotropy Constants from (110) and (001) Deposits
Authors: Lord D. G. , Goddard J. 
Published: July 2007

AbstractA study of the magnetocrystalline anisotropy of electrodeposited (001) and (110) single crystal f.c.c. Co—Ni films of thicknesses between 100 and 1000 Åhas been carried out, at 20 °C, by torque magnetometry. The composition dependence of K1 from the thicker films is found to agree with previous results from bulk alloys of the Ni‐rich compositions, but, apart from the work of Andrä and Spinarke (1969), differs from previous results from thinfilms. The constants K2 and K3 have been measured and have both been found to be negative over the whole composition range.
A Comparison of the Effects of Systematic Reflections on Extinction Contours in Bright‐ and Dark‐Field Images of Wedge Crystals
Authors: Sheinin S. S. 
Published: July 2007

AbstractThe dependence of the fringe spacing of extinction contours on crystal orientation has been studied in bright‐field images of wedge crystals of silicon. Crystal orientations were chosen so that either the (111) or (220) set of systematic reflections was excited. Comparison of the results obtained with extinction contours in (111) and (220) dark‐field images shows that when effects of systematic reflections are weak, as in the (220) case, there are no significant differences between bright‐and dark‐field contours. When effects of systematic reflections are strong however, as in the (111) case, bright‐ and dark‐field extinction contours are markedly different. Thus, for example, at certain crystal orientations the brightfield intensity profiles show the complex structure characteristic of the effects of multiple reflections whereas the dark‐field images, for the same diffracting conditions, are two‐beam in character.
Observation of X‐Ray Stacking Fault Fringes in the Plane Wave Case
Authors: Sauvage M. , Malgrange C. 
Published: July 2007

AbstractX‐ray stacking fault fringes in a silicon wafer are observed in the plane wave case by use of a double crystal spectrometer. Agreement with the theory is checked for two different radiations (AgKα and CuKα) and various values of the departure from Bragg angle. The nature of the fault, previously studied by X‐ray topography, is determined on the basis of the first extremum criterion in high absorption conditions. As expected, the results are closely related to those obtained in the electron case.
Lattice Vibrations of Cu2O at the Long Wave Limit
Authors: Carabatos C. 
Published: July 2007

AbstractA study of the lattice dynamics of cuprite at the centre of the Brillouin zone is made and the force constants and the effective charge deduced. The energies of the optically inactive phonons are calculated and their symmetry determined. The symmetry of the upper valence band of the crystal is identified.
Electron Microscopic Investigation of the Dislocation Structure in Molybdenum Single Crystals Deformed in Tension at 293 and 493 °K
Authors: Luft A. , Kaun L. 
Published: July 2007

AbstractThe dislocation structure of high purity molybdenum single crystals after weak tensile deformation at 293 and 493 °K is studied by transmission electron microscopy. The transition from parabolic stress—strain behaviour to three‐stage hardening which occurs between the considered temperatures is associated with a basic change in the deformation substructure. Crystals deformed at 293 °K contain a uniform distribution of long primary and secondary screw dislocations. On the contrary, the dislocation structure in stage I at 493 °K consists mainly of isolated clusters of primary edge dipoles. It is concluded that the effect of temperature on the mobility of screw dislocations is responsible for the change observed both in work‐hardening characteristics and related dislocation structures.
Temperature Dependence of the Davydov Splitting in Anthracene
Authors: Kurik M. V. , Piryatinskii Yu. P. , Popel O. M. , Frolova E. K. 
Published: July 2007

AbstractThe Davydov splitting for photoconductivity and absorption in anthracene has been measured in a wide temperature range. A phenomenological theory is developed which explains qualitatively the observed regularities.
DC Ionic Conductivity of Potassium Azide
Authors: Maycock J. N. , Verneker V. R. Pai , Gorzynski C. S. 
Published: July 2007

AbstractThe electrical conductance of both single crystal and pressed pellets of potassium azide has been measured. The ionic conductance parameters of KN3 were calculated from samples containing known amounts of Ba2+ ion impurity. The conventional theory of association was found to be adequate to describe association between Ba2+ and cation vacancies. A value of 0.2 eV was determined for — ζ, where ζ is the free energy of association of complexes. The following point defect parameters were determined: h, the enthalpy change for the formation of a defect pair = 1.25 eV, Δh, the enthalpy for migration of a cation vacancy = 0.76 eV, s, the entropy change on the formation of a defect pair = 0.119 × 10−3 eV deg−1. Equations describing X0, the number of thermally produced defects in a pure crystal, and μ, the mobility of the cation vacancy, both as a function of temperature have been derived.
Domain Structure of Uniaxial Antiferromagnets. The Problem of Nucleation
Authors: Mitsek A. I. , Gaidanskii P. F. , Pushkar V. N. 
Published: July 2007

AbstractThe dependence of the energy γ180 and the halfwidth δ180 of 180° L‐domain walls in antiferromagnets on the magnetic field H is calculated for low fields. At H → H0 (H0 is the critical field of the spin‐flop transition) the walls expand and their energy γ180 decreases. In the spin‐flop region 90° domain structure appears. γ90 and δ90 are determined by the value of fourth‐order anisotropy constant K2. The calculation of the metastable state (K2 <0) region shows that its boundaries may be approximated by the astroid at |K2| ≪ K1 only. The wall displacement in the spin‐flop region (K2 ≪ 0) and the domain structure at K2 > 0 are discussed. The problem of the new magnetic phase nucleation is considered.
Excitonic Electroreflectance of CuCl
Authors: Mohler E. 
Published: July 2007

AbstractTransverse electroreflectance measurements have been performed on CuCl single crystals in the region of the exciton bands. The observed changes of reflectivity can be separated into two components corresponding to a linear and a quadratic Stark effect of the excitons. The linear Stark effect is due to a splitting of the valence bands of CuCl, whereas in the case of the quadratic Stark effect the relative motion of the electron–hole pair is influenced by the electric field.
Anisotropy Investigations by Electrical Potential Measurements on Surfaces of P‐ and As‐TCNQ Single Crystals
Authors: Zosel D. , Ritschel H. , Hänsel H. 
Published: July 2007

AbstractA one‐probe measuring method has been used for electrical potential measurements on different planes of naturally grown single crystals of triphenylmethylphosphonium 7, 7, 8, 8‐tetracyanoquinodimethane (P‐TCNQ) and triphenylmethylarsonium 7, 7, 8, 8‐tetracyanoquinodimethane (As‐TCNQ). Potential distributions which result from using pairs of circular and straight plate electrodes in different arrangements on the crystal planes have been investigated. The explanation and description of the measured plots of the equipotential lines with a model is possible in a simple way for the (100) plane by using an anisotropic resistance net because in this case it is possible to reduce the three‐dimensional potential problem to a plane one. The electrical potential measurements give another contribution to the explanation of the interrelations between the crystal structure and anisotropic electrical properties of P‐ and As‐TCNQ.
Hole Effective Masses in Highly Doped CdSb Determined from Infrared‐Plasma‐Reflectivity Measurements
Authors: Rheinländer B. 
Published: July 2007

AbstractThe infrared plasma reflectivity is measured on heavily Ag‐doped CdSb with hole concentrations of p = (0.7 to 3.0) × 1019 cm−3 in the spectral region λ = 3 to 30 μm at T = 85 and 300 °K. Conductivity effective masses and relaxation times of holes are determined from the plasma frequencies obtained by fitting experimental and theoretical reflectivity spectra. The masses are strongly anisotropic and weakly temperature dependent. The relaxation times for optical frequencies are slightly greater than those according to Hall mobilities. Scattering of holes on ionized impurities is concluded to be predominate in the relaxation mechanism.
Charge Carrier Injection by Excitons at a Tetracene (Anthracene) – Electrolyte Interface
Authors: Vaubel G. 
Published: July 2007

AbstractThe influence of oxygen in electrolytic contacts on extrinsic photocurrents in tetracene and anthracene crystals is investigated. By adding Na2SO3 to the electrolytic electrode it is possible to vary the O2 partial pressure by orders of magnitude. It is found that triplet induced hole currents are controlled by a reaction of triplet excitons with oxygen, while singlet exciton induced hole currents must be produced by a specific exciton‐water reaction. On the other hand it is found that Na2SO3 stimulates an electron injection i.e. sulfit ions can act as electron donor upon interaction with triplet excitons. A kinetic analysis of the results is presented.
Dislocation Invisibility in Dark‐Field Electron Microscopy
Authors: Dingley D. J. 
Published: July 2007

AbstractA study has been made of conditions governing dislocation invisibility in dark‐field electron microscopy when the usual invisibility criterion g · b = 0 is not satisfied. Experiments were conducted on f.c.c., b.c.c., and h.c. p. metals. Anomalous invisibilities of dislocations were observed in each case and also when using high order or low order reflection s. Computer produced dislocation profiles indicated that the occurrence of anomalous invisibility is strongly dependent on the foil thickness to extinction distance ratio. The effects of this on the validity of past measurements of Burgers vectors using electron microscopy techniques are discussed. It is concluded that although errors must have been incurred in the past, they would only constitute a minor fraction of the data obtained.
Crystal Field Parameters of Ho3+ in YPO4
Authors: Becker P.‐J. 
Published: July 2007

AbstractSets of crystal field parameters are derived to describe the splittings of the 5F', the 3K'8, the 5G'6, and the 5G'4,5 levels of Ho3+ in YPO4 separately. The differences of the A〈r2〉 parameter for different levels by a factor of about 20 are explained qualitatively by different shielding factors for electrons in different LS‐states.
Double‐Plasmon Excitation in a Free‐Electron Gas
Authors: Ashley J. C. , Ritchie R. H. 
Published: July 2007

AbstractThe interaction of a fast charged particle moving in a free‐electron gas is described in the random phase approximation (RPA). The mean free path for the second order process of double‐plasmon excitation in the free‐electron gas is calculated. We find that the inverse mean free path for the double‐plasmon excitation process is related to the inverse mean free path for single plasmon excitation by λ = 0.0103 rλ−1p. Thus, for electron densities corresponding to those in a real metal (1 < rs < 6) double‐plasmon excitation may be important in the interpretation of certain experimental results as, for example, characteristic energy loss measurements.
The Effective Mass Tensor in Uniaxially Stressed n‐Type InSb
Authors: Zukotński S. , Saleh N. 
Published: July 2007

AbstractIn a previous paper [1] the plasma minimum in anisotropic semiconductors was theoretically analysed. In the present paper, degenerate n‐type InSb is considered and the anisotropy is induced by applying uniaxial stress. Using the theory developed by Bir and Pikus [2] the effective mass tensor is derived for stress applied in the [110], [100], and [111] directions. Measurements of the plasma minimum for samples stressed along the [100], [110], and [111] directions are presented and the effective masses are calculated. The results are used to obtain the value of the deformation potential (−40.8 eV) and of the band parameters a, b, and d (−88, −0.17, and −4.6 eV).
Magnetic Domain Wall Motion and Increase of Coercive Field
Authors: Bostanjoglo O. 
Published: July 2007

AbstractThe magnetic reversal in inhomogeneous iron and coarse grained cobalt films was investigated at 300 and 4 °K by Lorentz microscopy. The strong increase of the wall coercive field with decreasing temperature results in nucleation of numerous reversed domains at low temperature thus considerably changing the wall motion.