bluuebunny/crossref_metadata_2025_split huggingface dataset:
Helical density waves and the oscillistor effect in the electron hole plasma of the n‐Type ge (theory)
Authors: Schulz M. 
Published: July 2007

AbstractThe behaviour of a surface density wave during amplification by parallel electric and magnetic fields in a homogeneous plasma of a cylindrical Ge crystal has previously been investigated by Hurwitz and Mcwhorter for the case of low surface recombination. This theory is extended here to the case of an inhomogeneous plasma and made applicable to the oscillistor effect, in which a helical density wave occurs spontaneously above certain threshold fields. It is assumed that the wave behaves locally as for a homogeneous plasma, but that the behaviour varies with plasma density. In the two extreme cases of strong and weak injection, with respect to thermal carrier concentration, explicit solutions of the basic equations are presented including finite surface recombination. The dynamic behaviour of the plasma is investigated by perturbation theory for the case of surface density waves. The results for the propagation and amplification of the wave as well as the results of the instability investigation are compared quantitatively with experiment. For high‐injected carrier concentrations the phase velocity is dependent on the magnetic field and is higher than the ambipolar drift velocity. The instability occurs in a region a small distance behind the p—n‐junction, while all other parts of the sample remain stable.
An experimental investigation of dislocation‐phonon scattering in some copper alloys
Authors: Charsley P. , Salter J. A. M. , Leaver A. D. W. 
Published: July 2007

AbstractThe thermal conductivities of polycrystalline copper alloys, containing 2.8, and 12 at% aluminium and 30 at% zinc, have been measured between 1.5 and 4.2 °K in the annealed state and after tensile deformations up to 12%. Measurements of the dislocation densities in the alloys were made by transmission electron microscopy. It has been found that the scattering power of phonons by unit dislocation density increases linearly with the atomic concentration of aluminium. It would appear that the effect of zinc additions is negligible and that changes in the arrangements of the dislocations does not affect the effective scattering power.
Electron microscopy of high‐temperature Nb2O5 and related phases
Authors: Allpress J. G. , Sanders J. V. , Wadsley A. D. 
Published: July 2007

AbstractCrystals of high‐temperature niobium pentoxide (HNb2O5) and some mixed niobium‐tungsten oxide phases were examined by transmission electron diffraction and microscopy. The diffraction patterns and images of lattice fringes are fully consistent with the previously reported structures determined by X‐rays from the same samples. Irregularities in the lattice fringes, caused by faulting, were very rare in HNb2O5, but common in the mixed oxide phases.
Ultrasonic attenuation of anisotropic superconductor in ql < 1 limit
Authors: Yeh R. H. T. 
Published: July 2007

AbstractThe ultrasonic attenuation coefficient αs, for an anisotropic superconductor in ql < 1 limit, is expressed in terms of power series expansion of the parameter of anisotropy, a. We showed that the αs anomaly as proposed by Kadanoff and Pippard cannot occur. This is because there exist geometrical factors in the expression ofαs, which are sufficient to compensate the divergence in the relaxation time.
Theoretische Untersuchung der Keimbildung in Ferromagnetika
Authors: Holz A. 
Published: July 2007

AbstractDie theoretischen und experimentellen Untersuchungen zur Keimbildung in Fe‐Whiskern werden kurz diskutiert. Es wird vorgeschlagen, die als Brownsches Paradoxon bekannte Diskrepanz zwischen Theorie und Experiment für Teilchenradien größer als 1000 Å auf den Einfluß des Streufelds an der Stirnfläche zurückzuführen. Gestützt wird diese Annahme durch ein einfaches Modell, auf Grund dessen sich der Auslenkungsprozeß der Magnetisierung aus der Vorzugsrichtung in Abhängigkeit des äußeren Magnetfelds beschreiben läßt. Für schwache äußere Magnetfelder ergibt sich, daß sich die Magnetisierung nahezu senkrecht zur Probenachse einstellt.
Photothermoelectric effects in CdS
Authors: Weichman F. L. , Lomnes R. K. , Zukotynski S. 
Published: July 2007

AbstractThe theory of the change of the thermoelectric power under strong illumination of a photoconductor is developed for a number of different cases, including excitation of one type of carrier only. Experiments on CdS crystals gave a temperature independent ordinary thermoelectric power _1.14mV/deg over the range from 40 to 110 °C. Whereas the theory predicts a decrease in the absolute value of the thermoelectric power proportional to ln [σ(light)/σ(dark)], the experiments show an increase in absolute value with the same dependence on the conductivities. A possible reason for the discrepancy is discussed.
Zyklotronresonanz im Tellur
Authors: Herrmann R. , Herrmann Karin 
Published: July 2007

AbstractMit Zyklotronresonanzmessungen wurden zwei diamagnetische Resonanzen in der (1000)‐Ebene und eine diamagnetische Resonanz in der (0001)‐Ebene ermittelt. Die entsprechenden effektiven Massen werden berechnet und diskutiert. Neben den diamagnetischen Resonanzen treten noch zwei neue Resonanzerscheinungen auf.
Zur Fermifläche von Wolfram und Molybdän
Authors: Herrmann R. 
Published: July 2007

AbstractDie absoluten Werte der effektiven Massen von Wolfram und Molybdän werden verglichen. Für gleiche Bahnen auf der Fermifläche verhalten sich die entsprechenden effektiven Massen von Molybdän und Wolfram wie 1,3:1. Für beide Metalle ergeben sich unterschiedliche Abweichungen vom berechneten Modell der Fermifläche. So entspricht der Resonanz Pim Wolfram ein Oktaeder und im Molybdän eine Kugel.
X‐Ray interference fringes and domain arrangements in Fe + 3 wt% Si single crystals
Authors: Kuriyama M. , McManus G. M. 
Published: July 2007

AbstractExperimental observations on the anomalous transmission of X‐rays through a single crystal of Fe + 3 wt % Si having a regular domain arrangement are reviewed and discussed. The contrast lines present in these transmission photographs are interpreted as X‐ray interference fringes which are shown to run perpendicular to the domain boundaries seen on the crystal by the Bitter technique. From the presence of fringes in both the anomalously diffracted and transmitted beams it is inferred that the dynamical theory of X‐ray diffraction is necessary to explain this effect. The orientation of these fringes and their appearance and disappearance as a function of the diffracting plane are derived using the dynamical theory of diffraction in a medium containing magnetic domain boundaries in the path of the X‐ray beam. The observed dependence of fringe spacing on X‐ray wavelength is also quantitatively explained by this calculation.
Production d'ions et d'électrons par interaction avee la matière d'un faisceau de lumière cohérente
Authors: Gauthier R. , Bois D. , Pinard P. , Davoine F. 
Published: July 2007

AbstractL'interaction d'un faisceau de lumière cohérente avee diverses substances conductrices, semi‐conductrices et isolantes, donne naissance: à une émission électronique et ionique, en phase avec l'impulsion laser, qu'on peut attribuer à la présence de gaz adsorbé par la cible; à une émission d'ions et d'électrons, apparaissant avee uncertain retard et provenant vraisemblablement d'un effet thermique.
A remark on the derivation of the indirect interaction between nuclear or ionic spins
Authors: Vertogen G. , Caspers W. J. 
Published: July 2007

AbstractIn order to analyse the effect of many‐particle excitations on the indirect interaction between nuclear or ionic spins the fourth order contribution to the ground state energy is calculated. This contribution appears to be divergent. This is due to the fact that the contributions of the disconnected diagrams and the irregular part of the fourth order operator do not cancel each other, which is a consequence of the commutator properties of angular momentum operators. It is therefore concluded that the derivation of the R.K.K.Y. interaction on the basis of Rayleigh‐Schrödinger perturbation theory is of doubtful validity.
Ground state of a system with ferromagnetic s‐f interaction
Authors: Vertogen G. 
Published: July 2007

AbstractThe perturbation expansion is obtained for a free electron gas interacting with a nuclear or ionic spin system via a ferromagnetic s—f‐interaction. No divergent terms appear in the expansion if the unperturbed ground state of the system is assumed to consist of a polarized electron gas and a ferromagnetic spin system. This assumption is made plausible by considering the diagonal part of the perturbation and minimizing the resultant energy with respect to both the polarization of the electron and the structure of the spin system. In this way an energy up to second order in J is also obtained, and this is lower than the R.K.K.Y. result for a ferromagnetic spin system. No corrections to the magnetization of the spin system appear up to first order in J.
Quantum theory of thermogalvanomagnetic phenomena (TGMP) in conductors with equal concentration of electrons and holes
Authors: Guseva G. I. , Zyryanov P. S. 
Published: July 2007

AbstractFor the case of a magnetic quantization field a method is developed to calculate the conductivity current and heat flow up to terms of 1/(Ωτ) 2; Ω and τ being the cyclotron resonance frequency of the carriers and the relaxation time, respectively. The kinetical coefficients, determined by these currents, are necessary for the investigation of TGMP in conductors with equal concentrations of electrons and holes and also of the oscillations of the Hall constant in normal conductors. For the scattering on a short‐range potential the dependence of σ(2)xy on the magnetic field is analysed.
On the theory of weak ferromagnetics
Authors: Mitsek A. I. , Kolmakova N. P. 
Published: July 2007

AbstractThe magnetic properties of orthorhombic weak ferromagnetics are investigated by the double‐time Green function method in the Heisenberg model. To solve this problem the method of successive approximations suggested in [1] is used. The magnetization curves of the single domain orthorhombic weak ferromagnetics for non‐zero temperature and the frequencies of antiferromagnetic resonance (AFMR) in two sublattice models at 0 °K are calculated. The way of the calculation of the temperature dependence of thermodynamic parameters and AFMR frequencies is outlined.
Electrical Resistivity Studies of Iron–Nitrogen Solid Solutions
Authors: Wagenblast H. , Arajs S. 
Published: July 2007

AbstractThe electrical resistivity of iron–nitrogen solid solutions prepared from high purity iron has been studied as a function of applied longitudinal magnetic fields up to 60 kOe at 4.2°K. It is demonstrated that the presence of interstitial nitrogen increases the resistivity of iron and alters the shape of resistivity vs. magnetic field curves, particularly at low fields. By extrapolating the data to B = 0, where B is the internal magnetic induction, it has been possible to determine that the residual resistivity contribution per 1 at% nitrogen in solid solution in iron is about 0.1 μΩcm. At 78°K the value is approximately 7.0 μΩcm. Such a large positive deviation from the Matthiessen rule is characteristic for iron alloys with another transition metal as a solute. Magnetoresistivity data of iron‐nitrogen solid solutions (but not pure iron) very approximately obey the Kohler rule.
Statistics of Inter‐Impurity Recombination of Electrons and Holes in Semiconductors
Authors: Karageorgy‐Alkalaev P. M. , Leiderman A. Yu. 
Published: July 2007

AbstractRecombination statistics for semiconductors are derived taking into account transitions between impurities forming spatially localized recombination pairs. Expressions for the recombination rate and lifetime are given. The cases of weak and strong deviations from the thermodynamic equilibrium are studied.
Critical Exponents in the Dynamics of an Isotropic Magnetic System near its Transition Temperature
Authors: Villain J. 
Published: July 2007

AbstractOur model for critical magnetic relaxation [1, 7] is extended to the case when the static critical exponent η is not zero. It is applied to the derivation of dynamical scaling laws from weak assumptions. The dynamical critical exponent is found to depend on η in ferromagnets, but not in antiferromagnets.
Die Elektrolumineszenzeigenschaften von ZnSCu in Abhängigkeit von der Art des Koaktivators
Authors: Kawski A. , Horodecki A. J. 
Published: July 2007

AbstractEs wurde der Einfluß verschiedener Koaktivatoren, wie Chlor, Brom und Jod, auf die Ausbildung grüner bzw. blauer Lumineszenzzentren in ZnSCu‐Luminophoren untersucht. Die Präparation der Leuchtpulver erfolgte nach zwei verschiedenen Methoden. Es wurde festgestellt, daß man bei großen Eingangskoaktivatorkonzentrationen im Falle von Cl und Br das grüne, dagegen im Falle von J das blaue Elektrolumineszenzspektrum erhält. Auf Grund der Versuchsergebnisse kann die grüne Emission Schwefelatomen auf Zwischengitterplätzen, die blaue Zinkleerstellen zugeschrieben werden.
Direct Observations of Ferroelectric Domains in Lithium Niobate
Authors: Wicks B. J. , Lewis M. H. 
Published: July 2007

AbstractFerroelectric domain walls have been observed in LiNbO3 by transmission electron microscopy. The antiparallel nature of the polar transition has been confirmed by contrast analysis. The pinning of domain walls by lattice dislocations is attributed to an interaction with the hydrostatic stress field of an edge dislocation. It is suggested that this interaction may impede the formation of single‐domain crystals using applied electric fields near the Curie temperature.
Resistance Anomaly in Palladium–Silver Alloys Containing Rare Earth Impurities
Authors: Chen C. W. , Edwards L. R. , Legvold S. 
Published: July 2007

AbstractElectrical resistivities of Pd and three Pd–Ag alloys containing small amounts of Gd and Nd are shown to display varying anomalies at low temperatures. With decreasing temperature, the resistivity‐temperature curves show (i) an accelerated decrease of resistivity at temperatures below some characteristic temperature. Td, in the binary Pd alloys, (ii) a minimum in the tertiary Pd0.5Ag0.5 alloys, and (iii) a minimum and a sharp maximum in the tertiary Pd0.35Ag0.65 and Pd0.25Ag0.75 alloys. The present alloys, which constitute a continuous series of solid solutions having a common magnetic impurity, have thus exhibited a gradual shift from one to another of the three possible types of resistance anomalies predicted for dilute magnetic alloys by Kondo and other workers. The shift implies that a dominant role is played by the host lattice in the mechanism leading to a resistance anomaly.
Radiation Hardening of Neutron‐Irradiated Copper Single Crystals. I. Experimental Results
Authors: Rühle M. 
Published: July 2007

AbstractThe temperature and strain rate dependence of the critical shear stress (CSS) of neutron‐irradiated copper before and after annealing were measured between 4 and 500 °K. Measurements of the CSS of neutron‐irradiated gold are also reported. By means of electron microscopy the density and size distribution of observable defects in identically irradiated copper foils were counted. Since a fairly wide size distribution was found, the interpretation of the CSS‐measurements is not simple. The quantitative interpretation of the experimental results will be given in part II [2] on the basis of Frank's “spectrum theory” [1].
Radiation Hardening of Neutron‐Irradiated Copper Single Crystals. II. Interpretation
Authors: Frank W. , Rühle M. , Saxlová M. 
Published: July 2007

AbstractIt is shown that the vacancy‐type Frank dislocation loops on {111} planes observed in neutron‐irradiated copper by means of electron microscopy lead to a decrease in the mobility of glide dislocations during plastic deformation which accounts quantitatively for the enhancement of the critical shear stress of copper single crystals caused by neutron irradiation. This follows from the analysis of measurements of the critical shear stress and of electron‐microscopical determinations of the loop density in terms of a statistical theory of thermally activated dislocation motion over barriers of different heights. No adjustable parameters enter this analysis.
Jahn‐Teller‐Aufspaltung einer ESR‐Linie
Authors: Böttger H. 
Published: July 2007

AbstractDie Linienform der ESR‐Absorption von Ionen mit S = 1 auf kubischem Gitterplatz wird bei Berücksichtigung der Spin‐Phonon‐Wechselwirkung mit einer Diagrammtechnik berechnet. Es wird gezeigt, daß bei einer in den Phononen linearen Spin‐Phonon‐Wechselwirkung die Diagramme 4. Ordnung Terme liefern, die zu einer Linienaufspaltung führen können. Eine quantitative Abschätzung der Linienaufspaltung wird für Ni++ in MgO durchgeführt.
Influence of Impurities on Dislocation Velocities Controlled by Jog‐Dragging
Authors: Messerschmidt U. 
Published: July 2007

AbstractThe dislocation velocities in ionic crystals can be interpreted by the jog‐dragging mechanism in the low velocity range. At the initial slip stage part of the thermal jogs is transferred into a nonconservative moving configuration. This process is affected by impurity‐pinning points. Thus, the mean distance l between nonconservative jogs is defined by the impurity concentration cp as l = const b c. The dependence of the dislocation velocity of ionic crystals on stress, temperature, and impurity content can be explained by this concept and agrees well with experimental data published in the literature.
Deutung der Anisotropie der galvanomagnetischen Effekte im Tellur durch anisotrope Streuung
Authors: Rothkirch L. 
Published: July 2007

AbstractIm Rahmen eines Einellipsoidmodells für die E(k)‐Flächen werden die Koeffizienten der Leitfähigkeit, des Halleffekts und der magnetischen Widerstandsänderung für eine anisotrope Relaxationszeit berechnet, die invariant gegen die Symmetrieoperationen der Punktgruppe D3 ist. Damit ist eine Deutung der Anisotropie der galvanomagnetischen Effekte im Tellur möglich.
Sound Wave Velocity Change due to the Magnon‐Phonon Interaction
Authors: Lord A. E. 
Published: July 2007

AbstractA calculation is given of the sound wave velocity change, in a ferromagnetic dielectric, due to the magnon‐phonon interaction. Results are given for a low temperature region. For a normal magnetoelastic ferromagnet, like YIG, the changes turn out to be too small to measure, and the changes are just measureable in highly magnetostrictive materials (like the rare earth iron garnets). The temperature dependence of the low temperature results, taken together with earlier, more general, work in regard to the sound wave attenuation due to the magnon‐phonon attenuation, lead one to believe that a significant velocity change (Δv/v ≈ 10−2 %) should be seen in highly magnetostrictive materials at the higher temperatures, and a measureable change in YIG in the range 25 to 50 °K. The change should be separable from other changes, via its dependence on applied magnetic field.
Elektronenmikroskopie eingefrorener Versetzungen. I. Grundsätzliches zur Methode und Ergebnisse am Verformungsbeginn von Germaniumkristallen
Authors: Alexander H. 
Published: July 2007

AbstractBei 520 °C dynamisch verformte, unter Last abgekühlte Germaniumkristalle wurden mit Hilfe der Transmissions‐Elektronenmikroskopie untersucht. Es wird gezeigt, daß die Versetzungsanordnung sich weder beim Dünnen noch im Mikroskop geändert hat. Die Entwicklung der Versetzungsstruktur bis zur unteren Streckgrenze wird besprochen.
A Study of Curie Temperatures and the Effect of Carbon in Face‐Centered Cubic Iron–Nickel Alloys
Authors: Bolling G. F. , Arrott A. , Richman R. H. 
Published: July 2007

AbstractThe direct determination of Curie temperatures (θc) in metastable f.c.c. iron‐nickel solid solutions can be thwarted by a martensitic transformation. However, at the lower nickel contents, interstitially dissolved carbon which inhibits this phase transformation, fortuitously increases the propensity for ferromagnetism. An experimental scheme has been constructed for the determination of virtual Curie temperatures (θNi) down to 0 °K in these alloys. θc was determined (using a simple torque magnetometer) at various dissolved carbon levels for a given substitutional percent nickel; linear extrapolation to zero carbon was possible in each case. Derived results include: a linear variation, θ vs. nickel content, intercepting for 0 °K at ≈ 25 at% Ni; an approximately constant local effect of dissolved carbon, calculated for constant volume, from the observed dθc/dC, and known variations in these Invar‐type alloys; and the construct of ferromagnetic f.c.c. alloys at nickel contents as low as 22.6%.
Negative Magnetoresistance in p‐CdSb
Authors: Andronik I. K. , Arushanov E. K. , Emelyanenko O. V. , Nasledov D. N. 
Published: July 2007

AbstractNegative magnetoresistance is observed at low temperatures in cadmium antimonide crystals with hole concentration ≦ 5 × 1016 cm−3. The results of the investigation of the field, angular and temperature dependences in the temperature range 2.2 to 77°K of the magneto‐resistance of copper, silver, germanium, and tin doped samples with carrier concentrations ranging from 1016 to 1018 cm−3 are described. It is shown that the negative magnetoresistance is related probably to impurity band conduction. It is noted that the regularities observed, namely the quadratic dependence of the negative magnetoresistance on magnetic field strenght at weak fields and saturation at strong fields, the linear change of the negative magnetoresistance with temperature and the isotropy of the effect have the same character as in AIV and AIIIBV crystals and conform qualitatively Toyozawa's theory.
Optical Properties of GeSi Alloys in the Energy Region from 1 to 13 eV
Authors: Schmidt E. 
Published: July 2007

AbstractThe reflection spectra of GeSi alloys are measured in the photon energy range 1 to 13 eV at room temperature and in the photon energy range 1 to 6 eV at liquid nitrogen temperature. For these energy ranges also the dielectric constant ϵ1 + iϵ2 is calculated. The curves giving the dependence of the ϵ2‐spectra on the composition of the alloy show changes in the energy band structure in some critical points.
Anisotropy of Electroconductivity in CdSb
Authors: Anatychuk L. I. , Iskra V. D. , Luste O. J. , Rarenko I. M. , Zarubin L. I. 
Published: July 2007

AbstractThe anisotropy of the electroconductivity of p‐ and n‐type CdSb single crystals is investigated by a modified four‐probe method in the temperature range 5 to 500°K. In the interpretation of the experimental data obtained the energetic model proposed by Tovstyuk with three nonequivalent valence band maxima in the Γ point of the Brillouin zone and nonequivalent minima of the conduction band on the axes Σ, Δ, and Λ is used.
Polarized Luminescence of X‐Irradiated CaF2:Y and SrF2:Y Crystals and the Structure their Luminescence Centres
Authors: Görlich P. , Karras H. , Kötitz G. , Rauch R. 
Published: July 2007

AbstractY‐doped CaF2 and SrF2 crystals coloured subtractively by X‐rays at room temperature exhibit a broad luminescence band at 86°K in the near infrared if they are irradiated with light of the three long‐wavelength bands of the four‐band absorption spectrum. The peak of luminescence lies at 1.32 μm for CaF2: Y and 1.46 μm for SrF2:Y. The luminescence is partially polarized, the luminescence centres are oriented along the threefold axes ([111]‐directions). The results are shown to be in contradiction to earlier conceptions of the origin of the atomic centres in Y‐doped alkaline earth fluoride crystals. They are however compatible with a new model consisting of an electron trapped in a fluorine vacancy which is disturbed by a nearest neighbour Y3+‐ion.