bluuebunny/crossref_metadata_2025 huggingface dataset:
Untersuchungen der Bereichstruktur von Nickeleinkristallen III. Die Abschlußstruktur in zylindrischen Kristallen mit 〈110〉 als Achse
Authors: Spreen H.
Published: July 2007

Die Abschlußstruktur von zylindrischen Nickeleinkristallen mit 〈110〉 als Achse wird mit der Bitter‐Technik untersucht: Die senkrecht zur Stabachse gerichteten Magnetisierungskomponenten der Grundbereiche werden bei verschwindendem innerem Feld Hi von antiparallel zu den Grundbereichen magnetisierten Abschlußbereichen umgelenkt, deren Anordnung von der Oberflächenorientierung abhängt. Mit zunehmendem Feld Hi wird der Abschluß unabhängig von der Oberflächenorientierung mehr und mehr von magnetischen Streufeldern übernommen. Die Ladungen werden durch spezielle Oberflächenbereiche in das Kristallinnere verlagert.
Untersuchungen der Bereichstruktur von Nickeleinkristallen IV. Die Grundstruktur in zylindrischen Kristallen mit 〈100〉 als Achse
Authors: Spreen H.
Published: July 2007

Wir untersuchen an zylindrischen Nickeleinkristallen mit 〈100〉 als Achse die ferromagnetische Grundstruktur der Bereiche in niedrigen axialen magnetischen Feldern. Aus unseren Experimenten mit der Bitter‐Technik folgt zwangsläufig und widerspruchsfrei eine »zusammengesetzte Plattenstruktur«: Die Platten sind senkrecht zur Stabachse angeordnet: jede Platte umfaßt im wesentlichen vier Sektorbereiche. Die Sektorbereiche sind bei Hi = 0 Oe in einer leichten Richtung parallel zu der zugeordneten zweizähligen Oberfläche magnetisiert. Die zur Kristallachse senkrecht stehenden Magnetisierurgskomponenten haben innerhalb einer zusammengesetzten Platte einen Umlaufsinn, der von Platte zn Platte wechselt. Die vierzählige Symmetrie des 〈100〉‐Kristalls kommt somit in der magnetischen Bereichstruktur zum Ausdruck.
The Theoretical Strength of NaCl Crystals under Tension along its Body and Face Diagonals
Authors: Bartenev G. M. , Koryak‐Doronenko E. G.
Published: July 2007

Zwicky has proposed a method for calculating the theoretical strength of ionic crystals using Madelung's potentials for sign‐reverse rows. Using this method he has calculated the theoretical strength of NaCl crystals stretched along the edge of an elementary cube. This is a special case because the transverse compressive deformation along the y‐ and z‐axes is the same due tc the identical symmetry of the lattice in these directions. In the present paper Zwicky's method is generalized and extended to other directions of stretching in which contractions in mutually perpendicular directions are different. The theoretical strength and Young's moduli of NaCl crystals stretched along the body and face diagonals of an elementary cube are calculated.
EPR Study of Cu2+ Ion in Triglycine Fluoroberyllate
Authors: Stankowski J.
Published: July 2007

An investigation is made of the EPR spectrum of Cu2+ ions in ferroelectric triglycine fluoroberyllate. The values g∥ = 2.24 g∥ = 2.06, and A = 132 cm−1 are similar to those obtained for copper ions in triglycine sulphate and diglycine nitrate. The new lines are typical of S = 1 and the spectrum is found to have an anomaly at the Curie point. The D parameter of the spectrum is linearly dependent on the spontaneous polarization changes.
Inelastic Electron Scattering in Thin Films at Oblique Incidence
Authors: Geiger J.
Published: July 2007

Using the dielectric theory of inelastic scattering in thin films an equation is derived for the differential scattering probability for oblique incidence of the primary electrons. The dispersion relations for surface losses are discussed. The angular dependences of energy losses and energy gains are inverse.
Study of GaSb Valence Band by Magnetoresistance and Hall Effect Measurements at Low Temperature
Authors: Pistoulet B. , Robert J. L. , Marques M.
Published: July 2007

The presence of light and heavy holes in GaSb has been pointed out by Becker et al.[1] and values of their effective masses have been obtained by various authors [2,3,4]. A study is made here of the Hall effect, and the longitudinal and transversal magnetoresistance of p‐type GaSb crystals at 4.2 °K, from 0 to 33 kG. Assuming that depopulation of the light‐hole band by the field is mainly responsible for the variation of the Hall coefficient and considering isotropic bands tangential at k (000), the densities, mobilities, and effective masses of the two species of holes are deduced.
Mössbauer Effect in Ga2−xFexO3 and Related Compounds
Authors: Trooster J. M. , Dymanus A.
Published: July 2007

Mössbauer investigations are reported for five different compositions of gallium iron oxide and for iron‐substitutedβ‐Ga2O3, and AlFeO3. The spectra confirm the ferrimagnetic spin‐arrangement of Ga2−xFexO3. Information is obtained on the cation distribution in iron‐substituted (β‐Ga2O3 and Ga2−xFexO3.
Hot Electron Polar Scattering in InSb
Authors: Hammar C. , Weissglas P.
Published: July 2007

The energy and momentum relaxation of conduction electrons by optical phonons in InSb are studied using the energy band structure calculated by Kane. For simplicity, the drifted Maxwellian approach is used and its form for an arbitrary band structure is presented. No intrinsic breakdown is obtained. On the contrary, the model gives a voltage‐controlled differential negative mobility for high fields.
Stationary State of a Semiconductor with Negative Bulk Differential Conductivity
Authors: Kagan M. S. , Kalashnikov S. G. , Zhdanova N. G.
Published: July 2007

The system of nonlinear equations describing the stationary state of a semiconductor with negative bulk differential conductivity is analysed in the “phase plane”. The negative differential conductivity is considered to arise from either the field dependence of the electron concentration (due to the recombination process) or the field dependence of the mobility. Possible spatial variations of the field along the sample have a step‐like form and correspond to two different values of the saturation current. The current‐voltage characteristics and the field distributions are studied experimentally in n‐type germanium samples containing partly compensated copper. It is found that the saturation current corresponds to the peak of the current‐field curve of a spatially homogeneous sample. The electric field in the low and high field regions, as well as the location of these regions in the sample, are found to be in satisfactory agreement with theory.
Umwandlung von OH‐Zentren in U‐Zentren bei KCl‐Kristallen durch elektrolytische Verfärbung
Authors: Fröhlich F. , Adametz O.
Published: July 2007

Mit hilfe von Absorptionsmessungen im UV und IR wird gezeigt, daß sich durch elektrolytische Verfärbung von KCl‐Kristallen OH‐Zentren in U‐Zentren umwandeln lassen, falls die OH‐Ionen an Ca‐Ionen gebunden im Kristall vorliegen. Die Zahl der gebildeten U‐Zentren ist der Ausgangskonzentration der OH‐Ionen im Kristall proportional und nimmt mit der durch die Farbzentren übertragenen Ladungsmenge und mit steigender Temperatur zu. Gleichzeitig mit den U‐Zentren entstehen Absorptionsbanden im UV, die dem Sauerstoff zugeordnet werden können.
Jahn‐Teller‐Effekt an Übergangsmetallionen in Silberhalogeniden. I. Ti3+(3d1) und Fe2+ (3d6)
Authors: Koswig H. D. , Retter U. , Ulrici W.
Published: July 2007

Es werden die optischen Absorptionsspektren für den T2g → Eg‐übergang des Ti3+ und Fe2+ im AgCl und AgBr in Abhängigkeit von der Temperatur zwischen 20 und 400 °K untersucht. Die Aufspaltung dieses übergangs wird durch einen dynamischen Jahn‐Teller‐Effekt verursacht. Es wird die Temperaturabhängigkeit der Aufspaltung. der Lage der Maxima und der Flächen (Oszillatorenstärken) der Teilbanden bestimmt.
Orientation Superstructures and their Effects in Spinel Ferrites
Authors: Marais A. , Merceron T.
Published: July 2007

Orientation superstructures are examined using the magnetic diffusion after‐effect, the squareness ratio R, and the induced anisotropy Ku, in the ferrites: Mn0.2Fe2.8O4.014, CuxMg1−xFe2O4 (0.09 ≦ x ≦ 0.69), Mn1+xO4 (0.1 ≦ x ≦ 0.8) and Fe1.95Ni0.95Cox× × Zn0.1−xO4 (0.02 ≦ x ≦ 0.1). In the temperature zones where disaccommodation occurs (due to the ionic or electronic diffusion), a uniaxial anisotropy can be formed with a corresponding increase of R. It is shown that a new type of electron transfer: Cu+ ↔ Cu2+ is responsible for the magnetic after‐effect in Mg‐Cu ferrites.
The Symmetrized Combinations of Plane Waves for Wurtzite
Authors: Hejda B.
Published: July 2007

Tables of the coefficients of the symmetrized combinations of plane waves for wurtzite structure are constructed.
Zur Theorie der zweiphasigen Domänenstrukturen in Supraleitern und Ferromagneten
Authors: Hubert A.
Published: July 2007

Die Bereichsstrukturen in supraleitenden sowie einachsigen ferromagnetischen Platten unendlicher Ausdehnung werden theoretisch untersucht. Charakteristisch für diese Domänenstrukturen ist, daß die Bereiche im allgemeinen von der Plattenmitte zur Oberfläche hin in einer komplizierten Weise aufgespalten, derart. daß — besonders bei dicken Kristallen — die Bereichsweite an der Oberfläche viel kleiner als diejenige im Innern ist. Dieses Ver‐halten wird mit hilfe eines neuartigen Energieansatzes abgeleitet, in den wesentlich eine mittlere. stetig veränderliche Bereichsweite eingeht. Entscheidend sind drei für das jeweilige Material zu bestimmende Energieparameter, nämlich eine Wandenergie, eine Oberflächenabschlußenergie und eine Feldenergie im Inneren der Probe. Diese Parameter wer‐den sowohl für ferromagnetische als auch für supraleitende Proben angegeben. Mit ihrer Kenntnis ist es dann auf Grund der Rechnung möglich, die Bereichsweite in ihrem Verlauf von der Probenmitte zur Oberfläche als Funktion der Dicke der Probe, der Temperatur oder der Größe eines äußeren Feldes vorherzusagen.
Magnetic Dilution of Bare‐Earth Aluminum Cubic Laves Phases RAL2
Authors: Buschow K. H. J. , Fast J. F. , van Diepen A. M. , De Wijn H. W.
Published: July 2007

Curie temperatures and magnetizations are measured in the cubic Laves phases RxM1−xAl2 (R = Gd, Tb, Er and M = Y, La, Th). Upon dilution with Y or La a linear decrease of the Curie temperature, passing through zero for x = 0, is found. Dilution with Th results in an additional decrease of the Curie temperature. This effect is attributed to small changes of the Fermi wave‐vector. The results, as compared with Knight shifts, are discussed in terms of the Ruderman‐Kittel‐Kasuya‐Yosida theory. The exchange integral Γ is found to be of the order of −0.9 eV, and definitely negative.
Point Defects in Ferromagnets
Authors: van de Braak H. P. , Caspeks W. J.
Published: July 2007

A calculation is made of the local magnetization of the nearest neighbours of non‐magnetic impurities in a Heisenberg ferromagnet with spin quantum number equal to 1/2. For the higher temperatures below the Curie point a molecular‐field model is used. The results for the low‐temperature region, derived by method of the double‐time temperature‐dependent Green function, show that assumptions made in a previous study are valid.
On the Nature of Oscillations in Impurity Photoconductivity Spectra of Ge
Authors: Besfamilnaya V. A. , Elesin V. F. , Kueova I. A. , Ormont N. N. , Ostboborodova V. V.
Published: July 2007

A theoretical analysis is given which considers the strong dependence of lifetime on the carrier energy, the impurity scattering, and the very short relaxation time τop of the “hot” photocarriers due to optical phonons. The carrier energy is always smaller than the optical phonon energy and jumps from this value to nearly zero if the photon energy minus carrier ionizationsenergy is increased from just below to just above a multiple of the optical phonon energy. The main assumption made is that the lifetime of the carriers in this energy interval is solely determined by the relaxation time τac due to the acoustic phonons; the relaxation time with the equilibrium carriers τre and the lifetime rr of “cold” carriers being much greater. The relative depth η of the oscillations is calculated and is in good agreement with experiments on Ga‐doped p‐type germanium at 7 °K.
The temperature dependence of the borrmann effect in copper
Authors: Baldwin T. O.
Published: July 2007

The temperature dependence of the anomalous transmission of X‐rays (Borrmann effect) in copper has been measured in the temperature range 77 to 377 °K. From the slopes of the curves obtained, the apparent Debye temperature θ has been determined to be (306 ± 4) °K. This value is 3 to 4% less than that previously reported from the temperature dependence of X‐ray diffraction from powders and single crystals. Using this value of θ in the calculations of absolute Borrmann intensities, however, good agreement is obtained between calculated and experimental values. It is suggested that the difference in the θ‐values may arise from thermal diffuse scattering and/or anharmonic contributions to the temperature dependence of the Borrmann intensities.
Higher order elastic constants in H.C.P. crystals
Authors: Rose M. F. , Ramsey R. T.
Published: July 2007

Expressions for the elastic constants for hexagonal close‐packed lattices are derived through third order, assuming, the atoms interact through a central potential function These expressions are then evaluated, using the Morse and Rydberg potential functions, for Be, Mg, Zn, Cd, and Tl. Comparisons are made between theory and experiment wherever possible. The effect of the axial ratio of the h.c.p. lattice on the eleastic constants is discussed and it is shown that both potential functions lead to lattice instabilities for Zn and Cd.
Field electron microscope study of niobium surfaces
Authors: Savage William R.
Published: July 2007

An account is presented of field emission experiments on contaminated and clean niobium surfaces. It is concluded that the equilibrium thermal end‐forms of niobium single crystal emitters consist of small flat regions of low index crystallographic directions smoothly joined by transition planes to give a shape close to spheroidal. Fowler‐Nordheim graphs of the voltage‐current characteristics of the thermally cleaned cathodes gave a work function of (4.1 ± 0.1) eV which agrees with the results of other measurements.
Temperature dependence of the band structure
Authors: Sak J.
Published: July 2007

The temperature dependent part of the self‐energy of an electron interacting with acoustic phonons is computed. At low temperatures the shifts of critical points are quadratic in temperature. Points of the type M0 and M1 shift to lower energies whereas the points M2 and M3 shift to higher energies. For levels at general points there exists a region where the shift is proportional to T4. At high temperatures the direction of shift is determined by the energy of the level. Levels lying below a certain energy shift downwards, those lying above this energy shift upwards. The shift is then linear in temperature.
Surface self‐diffusion measurements on copper
Authors: Bonzel H. P. , Gjostein N. A.
Published: July 2007

The decay kinetics of sinusoidal surface profiles on copper annealed in a hydrogen atmosphere were investigated in the temperature range 600 to 1030 °C in order to determine the temperature dependence of the surface self‐diffusion coefficient, Ds. Below 910 °C the surface profiles were found to be faceted resulting in an apparent discontinuity in Ds which can be understood in terms of the γ‐plot of copper. The discontinuity in the diffusion data can be expressed by the following equations: magnified image
At temperatures below 800 °C is dependent on the annealing time, and inthe vicinity of 600 °C, Ds drops drastically below the minimumvalue that can be measured. This behavior can be explained in terms of the rate theory for a bimolecular surface reation between impurities and diffusing defects. From the predicted time dependence of Ds, it is possible to estimate Ds at t=0. These Ds−values are greater than the extrapolated high temperature data, thus indicating thepossibility of a lower activation energy for surface self‐diffusion at low temperatures.
The structure of amorphous silicon nitride films
Authors: Coleman M. V. , Thomas D. J. D.
Published: July 2007

In an amorphous material the scattered intensity of electron waves depends, in part, on its structure. The variation of the scattered intensity with angle may be mathematically transformed to give a radial distribution function (RDF) which describes both the position, number and type of atoms around an origin atom. The methods used to obtain the RDF from the structurally dependent intensity and the elimination of errors are described. To determine the scattered intensity experimentally, the electron diffraction pattern is scanned across a small aperture and the open circuit voltage developed in a silicon solar cell is measured. These methods have been used to determine the structure of amorphous silicon nitride films prepared by the glow discharge technique. By changing the ratio of ammonia to silane gases, the average composition of the deposit may be varied from silicon to silicon nitride. The effect of these and other deposition parameters on the structure of the films is described. The structure of these films is shown to consist of a mixture of silicon and silicon nitride. The effect of inelastic scattering on the RDF is discussed and the validity of the results confirmed.
Über verbotene Reflexe bei Elektronenbeugung an vakuumaufgedampften Tellurschichten
Authors: Schüz W.
Published: July 2007

Tellur wurde polykristallin im Hochvakuum aufgedampft und mit der “Sandwich‐Methode” zu dünnen Einkristallfolien im Elektronenstrahl umkristallisiert. Im Beugungsbild zeigten 3 Hauptorientierungen mit horizontaler c‐Achse neben den erlaubten Basis reflexen 00l = 3 n (n ganzzahlig) auch die verbotenen Reflexe 00l für l ≠ 3 n. Dies läßt sich meist als Umweganregung deuten, weil die Intensität der verbotenen Reflexe in einer Vielzahl von Beispielen von der der Nachbarreflexreihen 10l, 11l und 21l übertroffen wird. Andererseits sind gelegentlich verbotene Reflexe bei besonders starker Anregung eines unmittelbar benachbarten 003‐Reflexes zu beobachten, die die oben genannten Nachbarreflexreihen an Intensität weit übertreffen. Dies kann auf einen hierbei überwiegenden Einfluß von systematischer Wechselwirkung zurückgeführt werden.
Structure and dynamics of perovskite‐type crystals
Authors: Cochran W. , Zia A.
Published: July 2007

The connection between Landau's theory of phase transitions and the lattice‐dynamical theory of a displacive transition in a crystal is discussed. At a second‐order displacive transition the frequency of one normal mode becomes zero. By investigating the displacements of the atoms from special positions of the lattice for a number of crystals having the distorted perovskite structure, we have shown that several modes are involved in the various transitions, except in the case of LaAlO3, where the transition is probably second‐order or nearly so, and is associated with a mode of low frequency. The wave vector of this mode is at the point (1/2 1/2 1/2) of the Brillouin zone, and its irreducible representation is Γ25.
Potential differences in NaCl crystals due to plastic deformation by indentation experiments between RT and 20 °K
Authors: Fröhlich F. , Seifert P.
Published: July 2007

Electric potential differences due to plastic deformation by indentation are studied in pure and doped NaCl crystals as a function of temperature between room temperature and 20 °K. For CaCl2−doped crystals the potential difference over the whole temperature range can be explained by negatively charged dislocations, and for Na2O2−doped crystals by positively charged dislocations. In nominally pure crystals the potential differences change sign as the temperature is decreased. An interpretation of these results is suggested on the assumption of different temperature dependencies for trapping anion and cation vacancies in the dislocation core.
Energies of Formation of Metal Vacancies in II‐VI Semiconducting Tellurides (HgTe, CdTe, ZnTe)
Authors: Bailly F.
Published: July 2007

The energy of formation of metal vacancies in tellurides is calculated on the assumption that covalent bonding occurs between the Te neighbours. The model uses Morse functions to describe the bond strength between nearest neighbours and the approximation of Suchet's crystallochemical mode. The mean displacement of the atoms around the vacancy is calculated by minimizing the sum of the energy terms associated with the various interactions and is shown to be important. It is shown that, in the particular case of HgTe, this type of vacancy has a negative energy of formation (neglecting the interactions between vacancies). These defects are thus expected to occur naturally with a high concentration, and they are expected to behave as neutral defects. Previous experimental observations of “complex vacancies” support this conclusion. The bonds between Te neighbours may be broken at high temperatures, which transforms the complex vacancies into normal ones: the calculated energy of transformation is in fair agreement with experiment. In the cases of CdTe and ZnTe, the covalent bonding between Te neighbours has only a small effect on the energy of formation of a vacancy.The same kind of calculation, applied to the group IV elements, leads to an energy of formation of vacancies which is in good aggreement with other theoretical calculations and experimental determinations, and this supports the validity of the model.
Computer simulation of the plastic deformation in face‐centred cubic polycrystals and the rolling texture derived
Authors: Leffers T.
Published: July 2007

Using computer simulation of plastic deformation it is shown that both types of rolling texture found experimentally in f.c.c. metals and alloys may be developed by {111} <110> slip. A texture of the copper‐type is developed if the individual crystals are forced to follow the macroscopic deformation in accordance with Taylor's theory. If the grains are supposed to deform like isolated single crystals a brass‐type texture is developed.
Fehler im Flußliniengitter von Supraleitern zweiter Art
Authors: Träuble H. , Essmann U.
Published: July 2007

Das Flußliniengitter von Supraleitern zweiter Art enthält Gitterfehler, wie sie aus der Kristallphysik bekannt sind, nämlich Versetzungen, Stapelfehler, “Punkt” fehler usw. Außerdem treten starke elastische Verzerrungen und Gitterkrümmungen auf. Die verschiedenen Gitterfehler werden an Hand von Beispielen, die durch direkte Beobachtung gewonnen wurden, beschrieben und klassifiziert.
Noncentral force model for hexagonal close‐packed crystal lattices (ii)
Authors: Metzbower E. A.
Published: July 2007

A Born‐von Karman model of the hexagonal close‐packed crystal lattice was considered using a combination of central and angular forces between various sets of neighbors. The interactions between nearest neighbors in the plane were considered to be central forces while the interaction between both nearest and next‐nearest neighbors out of the plane were considered to be noncentral forces, i.e. the interactions involved both central and angular forces. The equations of motion were evolved and the atomic force constants were evaluated by three different methods. The atomic force constants were evaluated 1. from the elastic constants by the method of long waves, 2. from a least squares analysis of the eigenvalues of the secular equation for elastic waves propagating in certain symmetric crystallographic directions at critical points in the Brillouin zone, i.e. from a least squares analysis of the dispersion relations, and 3. from a least squares analysis of the elastic constants and the dispersion relations. The eigenvalues of the secular equation were calculated for a mesh of seven hundred thirty‐five (735) points in that portion (one twenty‐fourth) of the Brillouin zone irreducible under symmetry operations. The frequency spectrum was obtained from these eigenvalues. The lattice specific heats as a function of temperature were calculated using the appropriate frequency distribution function. The Debye and Einstein characteristic temperatures were also calculated as a function of temperature and compared to experimental values. The insensitivity of the calculated thermodynamic properties of the hexagonal close‐packed crystal lattice on the frequency spectrum is demonstrated for zinc by calculating three different frequency spectra, one for each method of evaluating the atomic force constants, and from these spectra computing the lattice specific heats as a function of temperature. The Debye characteristic temperatures do not change significantly although the details of the frequency spectra differ appreciably. The conclusion has been drawn that better agreement between theory and experiment is reached if angular forces are included in a model of the hexagonal close‐packed crystal lattice rather than simply extending the sphere of interaction to more and more neighboring atoms.
Delocalized excitons in thin anisotropic crystals
Authors: Evans B. L. , Young P. A.
Published: July 2007

The ordinary absorption spectrum of MoS2 contains two series of exciton absorption bands associated with direct optical transitions from a split valence band. In thick crystals the first five members of each exciton series have been detected; these exciton bands move to higher energies and show a diminishing diamagnetic shift with decreasing crystal thickness. The exciton series limit in thin crystals is determined from the oscillatory magneto absorption which occurs to the high energy side of the short wavelength series.
The effects of oxygen adsorption and low energy ion bombardment on the electrical properties of cadmium sulphide thin films
Authors: Hughes D. M. , Carter G.
Published: July 2007

The changes produced in the electrical properties of cadmium sulphide thin films following oxygen adsorption and low energy ion bombardment are reported. High purity cadmium sulphide thin films were prepared in an ultra high vacuum evaporating chamber and conductivity tests and adsorption and bombardment investigations were carried out without exposing the samples to atmospheric contamination. Changes in the electrical properties of the thin film samples which can be directly attributed to either oxygen contamination or radiation damage at the surface, were observed.
A model for tunneling through a Non‐Crystalline thin dielectric film
Authors: Schnupp P.
Published: July 2007

Continuing along the lines of an earlier paper [4] on the tunneling of electrons through a thin dielectric film using a one‐dimensional δ‐well model, the tunneling through a disturbed crystalline or amorphous dielectric is considered introducing an uneven spacing of the δ‐wells. As to be expected form the work of De Dycker and Phariseau on the band structure of unlimited amorphous materials [5] the complex band structure in the forbidden band is not qualitatively changed introducing a randomness in the location of the δ‐wells. Quantitatively one observes a decrease in damping x with increasing deviation from the ordered crystal.
Helical density waves and the oscillistor effect in the electron hole plasma of the n‐Type ge (theory)
Authors: Schulz M.
Published: July 2007

The 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

The 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

Crystals 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

The 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

Die 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

The 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

Mit 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

Die 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

Experimental 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

L'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

In 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

The 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

For 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

The 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

The 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

Recombination 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.
Magnetic Space Groups and their Irreducible Representations
Authors: Overhof H. , Rössler U.
Published: July 2007

In this paper magnetic space groups are defined. Their irreducible representations are given in terms of the irreducible representations of the group of the k‐vector. The irreducible representations of the double groups and time inversion symmetry are discussed.
Critical Exponents in the Dynamics of an Isotropic Magnetic System near its Transition Temperature
Authors: Villain J.
Published: July 2007

Our 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

Es 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

Ferroelectric 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

Electrical 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

The 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

It 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

Die 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

The 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

Im 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

A 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

Bei 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

The 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%.