bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermoelectric and Thermomagnetic Properties of n‐Ge in the Region of Phonon Drag Effects
Authors: Lutsyak V. S. , Nitsovich V. M. 
Published: July 2007

AbstractThe influence of phonon drag effects on thermoelectric and thermomagnetic properties of n‐Ge is investigated. The role of different scattering mechanisms is discussed. From a comparison of the experimental data [11, 13] with the theory follows that the theoretical values of the thermoelectric and thermomagnetic coefficients agree better with experimental ones assuming that the phonon relaxation times depend on the wave vector and temperature as it was predicted by Simons [2].
Anisotropy of Paramagnetic Spin‐Lattice Relaxation
Authors: Aminov L. K. , Klimachev A. F. 
Published: July 2007

AbstractSimple group‐theoretical arguments are used to derive the dependence of the relaxation transition probabilities with participation of an arbitrary number of phonons on the orientation of an external magnetic field relative to the crystal axes of the paramagnetic samples. The system of paramagnetic ions with arbitrary spin is investigated in the case of weak magnetic field, when the Zeeman splitting is much smaller than the crystal field splitting. However, the results may be directly transferred to the opposite case of |𝒳z|≫|𝒳cr|. An example of application of the results obtained is considered.
Correlation of Infra‐Red Spectra with Structural Distortions in the Spinel Series Mg(CrxAl2−x)O4
Authors: Grimes N. W. , Collett A. J. 
Published: July 2007

AbstractThe details of the infra‐red spectra over the range 200 to 1000 cm−1 are presented for eight members of the spinel series Mg(CrxAl2−x)O4 and correlated with the development of local distortions of C3v symmetry. It is shown that the frequency behaviour of two of the prominent absorption bands is described rather well by the equations given by Waldron for the modes labelled v1 and v3. Force constants k1 and k0, corresponding to unit displacements along the tetrahedral cation‐oxygen and octahedral cation‐oxygen bonds, respectively, are derived in a manner which allows for the presence of other interactions.
Computer Simulation of Electron Microscope Images
Authors: Maher D. M. , Perrin R. C. , Bullough R. 
Published: July 2007

AbstractA procedure has been developed which enables computer‐simulated electron micrographs of defects in crystalline foils to be constructed that are, photographically speaking, virtually indistinguishable from the corresponding experimental micrographs. The intensity variations in the image are simulated by constructing a suitable matrix of overprinted “dots” on the output of a Stromberg‐Carlson 4060 plotting device. These variations are quantitatively calibrated in the final micrograph against the corresponding optical densities. The number of grey levels generated by a given set of computer and photographic variables is sufficiently large to provide excellent tonal separation in the final simulated image and high resolution micrographs are readily achieved.
Dislocations in symmetric high angle [001] tilt boundaries in gold
Authors: Schober T. , Balluffi R. W. 
Published: July 2007

AbstractThe structure of high angle tilt boundaries possessing small tilt deviations (i.e., 1 to 2°) from various special high coincidence site density tilt misorientations was studied by transmission electron microscopy. The latter misorientations corresponded to rotations of θc = 22.6, 28.1, 36.9, 53.1, 61.9, 67.4, and 73.7° around [001]. The grain boundary planes were of the symmetric type, and the tilt deviations from the high coincidence site density misorientations were around various axes lying in the grain boundary planes. The boundaries were examined at normal incidence in bicrystals prepared by welding single crystal thin films together face‐to‐face at predetermined misorientations and also edge‐on in polycrystals obtained by the annealing of welded bicrystals initially containing only twist boundaries. Arrays of parallel dislocations were found in a number of boundaries which appeared to be in good agreement with the structures predicted by use of Bollmann's analysis of the geometry of dislocations in high angle grain boundaries. It is therefore concluded that the structure of such high angle boundaries consists of an array of evenly spaced edge dislocations (or possibly close pairs of dislocations in certain cases) running parallel to the tilt deviation axis embedded in the interface corresponding to the nearby high coincidence site density misorientation. It seems likely that such structures exist over wider ranges of misorientation than were investigated experimentally.
Temperature dependence of the EPR line width and a relaxation of Cr3+ ions in ZnWo4
Authors: Bugai A. A. , Glinchuk M. D. , Deigen M. F. , Maksimenko V. M. 
Published: July 2007

AbstractThe change of the EPR line width, shape, and angular dependence of the halfwidth of Cr3+ ions in ZnWO4 is investigated in the temperature range from 4.2 to 1200 °K. It is shown that the EPR line broadening at high temperatures is due to the spin‐phonon interaction. Two‐ and four‐phonon processes of Raman‐type play the main part in relaxation. Experimental data on high‐temperature line broadening are used to evaluate the spinlattice relaxation time at liquid helium temperature.
Elektronen‐störpotential inhomogen verzerrter kristallgitter
Authors: Teichler H. 
Published: July 2007

AbstractMit Hilfe der Wannier‐Formulierung wird ein effektives Störpotential aufgestellt, das den Einfluß endlicher, inhomogener Gitterverzerrungen auf die elektronischen Eigenschaften der Metalle beschreibt. Linearisierung in den Verschiebungsdifferenzen führt auf ein Störpotential, das vollständig durch Matrixelemente zwischen den Wannierfunktionen des ungestörten Kristalles und den Verschiebungen definiert ist.
Plural and multiple scattering of low‐energy heavy particles in solids
Authors: Meyer L. 
Published: July 2007

AbstractSmall‐angle multiple scattering of low‐energy heavy particles (Born parameter α > 1) in solid layers is calculated, using a scattering cross section derived from classical mechanics. The angular distribution of the scattered particles is given as a sum of two functions, which are tabulated. The calculated distributions coincide with those of the well‐known theory of Molière for large thicknesses of material. For small thicknesses there are profound deviations.
On the effect of exchange interaction on the impurity ion optical spectrum
Authors: Nikiforov A. E. , Cherepanov V. I. 
Published: July 2007

AbstractThe method of effective Hamiltonian (EFH) is applied to the excited state (2E4A2) fine structure of Cr3+–Cr3+ fourth order pairs in ruby. Comparison with experimental data illustrates the importance of both the anisotropic and antisymmetric exchange interactions, and that part of isotropic exchange interaction, which is nondiagonal in the orbital variables. Various microscopical mechanisms responsible for terms in the effective Hamiltonian are discussed.
Calculation of the induced magnetic anisotropy energy by means of Boltzmann statistics
Authors: Steinert J. 
Published: July 2007

AbstractInduced magnetic anisotropies are caused by changes of orientation or concentration of crystal defects. All possible sites of a defect will be got in a given crystal by application of elements of the point group which corresponds to the crystal class. In cubic crystals possible changes of the concentration of the defects due to the direction of magnetization does not influence neither the induced unidirectional nor the induced uniaxial anisotropy, but influence the induced biaxial anisotropy.
Le champ moléculaire du nickel
Authors: Munschy G. 
Published: July 2007

AbstractEn tenant compte des fluctuations de l'ordre magnétique dans la théorie de l'électron collectif de Stoner, on montre que le champ moléculaire hm(M) n'est pas proportionnel à l'aimantation M du métal ferromagnétique, mais qu'il comporte des termes correctifs en M3, M5, … Dans le cas du nickel, le champ obtenu est en assez bon accord avec les prévisions semi‐empiriques de Shimizu.
Some consequences of surface and size effects in plastically deformed copper single crystals
Authors: Mughrabi H. 
Published: July 2007

AbstractThe dislocation behaviour in deformed copper single crystals was previously shown to correspond to a lower local flow stress in the surface region than in the interior and the primary glide plane was found to undergo a characteristic bending in the surface region, reflecting a local excess density of unpaired edge dislocations. The detailed features of this “profile” are explained by a dislocation model which takes into account both surface and inner dislocation sources. It is shown that, as a result of the surface effects, dislocation glide paths in stage II as determined from slip lines are about 2.5 times larger than those in the interior. The rate of work‐hardening in stage II above a certain stress level, however, is found to be fairly constant over the cross‐section inspite of surface effects. It is concluded from Seeger's stage II work‐hardening theory that the number of dislocations per group should therefore decrease in the same way as the glide paths from the surface towards the interior. This prediction is in line with available experimental data. The shape of the macroscopic stress‐strain curve is explained by the local microscopic behaviour. Our results are consistent with Fourie's concept of preferential core‐hardening. The possibility of preferential near‐surface‐hardening is indicated.
The fine structure of beams in electron diffraction emerging from wedge‐shaped crystals. Multiple beam case
Authors: Serneels R. , De Ridder B. , Gevers R. , Amelinckx S. 
Published: July 2007

AbstractThe fine structure of electron diffraction beams emerging from a wedge‐shaped crystal is analysed on the basis of the dynamical multiple beam theory. First the basic principle of the Fourier‐transforms method and the method of the scattering matrix is summarized. The theory is applied to a wedge as well in a particular as in a general orientation. Assuming n strongly diffracted beams it is found that the transmitted and each strongly diffracted beam is composed of n + 1 sub‐beams with slightly different orientations. The geometry of the fine structure configuration is discussed and the influence of absorption effects on the intensity of the beams is examined. It is emphasized that the intensity of the different sub‐beams is directly related to the strength of excitation of the different Bloch wave fields in the crystal. The method is discussed explicitly for a particular multiple beam situation in MgO where the 400 reciprocal lattice vector is in the exact Bragg orientation and where only systematic reflections are supposed to be active. Taking account of absorption effects the situation is discussed within the three beam dynamical theory (000, 200, 400). Afterwards the influence of the systematic interactions (600, 500) is investigated. Three‐ and five‐beam calculations are compared with experiments. It is found that the observed fine structures (of the different beams) can be explained adequately by three‐beam theory.
Superconductivity in simple metals
Authors: Rajput J. S. 
Published: July 2007

AbstractThe superconducting state parameters for both nonsuperconductors and simple‐metal (nontransition‐metal) superconductors are evaluated using the exact OPW (orthogonalized‐plane‐wave) form‐factors based on the model pseudopotential of Heine and Abarenkov. An attempt is made to establish a criterion for the occurrence of superconductivity in non‐transition metals using the pseudopotential approach and it is inferred that more reliable values of the superconducting state parameters can be obtained using a correct pseudo‐potential and the phonon spectrum.
Dependence of magnetically induced anisotropy in a ferromagnetic single crystal on its block structure
Authors: Lesnik A. G. 
Published: July 2007

AbstractA general expression for the energy of induced anisotropy in ferromagnetic single crystals, obtained in a previous paper [1] is analyzed in detail. It is shown that the induced anisotropy constant Ku depends on the single crystal block structure and the direction of magnetic field during annealing.
Determination of structure factors of X‐rays using half‐widths of the Bragg diffraction curves from perfect single crystals
Authors: Kikuta S. 
Published: July 2007

AbstractFor determining precisely the absolute values of X‐ray atomic scattering factors (f‐values) the half‐widths of the Bragg diffraction curves of perfect single crystals are utilized. The principle of the method and the experimental procedure are described. Using a double‐crystal diffractometer of parallel setting with CuKα1 radiation, the f‐value for the 422 reflection of silicon was determined with an accuracy better than 0.3% in a favourable case, which is in good agreement with the theoretical one. Even strongly absorbing crystals can be used as specimens, a size of the perfect region of about 0.5 mm will be sufficient for the measurements. The present method seems to be promising.
Ferromagnetic resonance in single crystal nickel disks: Angular dependence of linewidth
Authors: Anderson J. R. , Bhagat S. M. , Cheng F. L. 
Published: July 2007

AbstractThe angular variation of the FMR linewidth in single crystal disks of nickel has been studied for both the in‐plane (H) ∥ sample surface) and out‐of‐plane (H ⊥ sample surface) geometries. For the in‐plane case the linewidth is essentially isotropic. For the out‐of‐plane geometry the effective linewidths exhibit a shallow minimum for M about 55° from the sample plane. For both geometries these results are consistent with a Gilbert type equation (including exchange conductivity effects) with an angle independent damping parameter.
Elastic Electron Scattering in InSb‐Type Semiconductors
Authors: Zawadzki W. , Szymańska W. 
Published: July 2007

AbstractRelaxation times for elastic electron scattering in III–V compounds of InSb type are calculated taking into account consistently the nonparabolic structure of the conduction band, both in the density of states and electron wave functions. The calculations are based on the Kane model of band structure, including explicitly mixing of p‐like components into the total wave function of the conduction band. Electron scattering by charged impurities and heavy holes, optical phonons (polar interaction), acoustic phonons, and piezo‐acoustic modes are considered. Screening by free electrons is included in the long‐range interactions and shown to play an important role at higher electron concentrations. Both spin‐conserving and spin‐flip transitions are considered for all modes. It is demonstrated that transverse branches participate appreciably in acoustic scattering at high electron energies. In all cases, the presented calculations give much higher values of the theoretical mobilities for heavily doped samples than those obtained up to now taking into account only the proper density of states.
Magnetic Pinch in n‐InSb
Authors: Holter Ø. 
Published: July 2007

AbstractEquations governing the magnetic pinch in semiconductors are derived taking into account the exclusion principle for high plasma densities. The equations represent two non‐linear coupled integral equations, which have to be solved numerically. The plasma distribution, the density on the axis, the self‐magnetic field, and the current‐voltage characteristic are calculated for a specified n‐InSb sample. The axial plasma density is shown to be larger than the thermal density of the crystal at the melting temperature, suggesting a minor role for thermal carrier generation in a fully pinched semiconductor plasma.
Anisotropie in kubischen Supraleitern
Authors: Obst B. 
Published: July 2007

AbstractMit der von Träuble und Essmann entwickelten Dekorationstechnik wurden magnetische Strukturen in kubischen Supraleitern untersucht. Im Zwischenzustand zeigt Blei bevorzugte Orientierungen der Phasengrenzen in bestimmten Richtungen. Die Anisotropieerscheinungen werden in Blei‐Thallium‐Legierungen als Funktion des Ginzburg‐Landau‐Parameters x verfolgt. Die beobachtete Anisotropie der spezifischen Grenzflächenenergie σNM läßt sich im Rahmen der phänomenologischen Theorie von Ginzburg und Landau nicht verstehen. Versuchsweise werden in das σNM‐Funktional für den isotropen Fall die mikroskopischen Größen eingesetzt und die Anisotropie allein durch den Parameter der Energielücke Δ beschrieben. Die sich so ergebende Orientierungsabhängigkeit von Δ wird mit theoretischen Vorhersagen verglichen.
Absorption and Fluorescence Spectra of Tm3+ in YVO4 and YPO4
Authors: Knoll K. D. 
Published: July 2007

AbstractThe optical absorption spectra of trivalent thulium in single crystals of YVO4 and YPO4 were measured in the range from 5000 to 29000 cm−1 including the Zeeman effect at 85, 4.2, and 2K. Furthermore the fluorescence spectrum in YVO4 between 19000 and 25000 cm−1 was investigated. Some special features of the spectra can be explained by the assumption that in several cases the crystal field eigenfunctions consist essentially of one free ion Ψγ J M. From the splitting of Tm3+ in YVO4 values for the crystal field parameters were determined.
Channel Conductivity of Cleaved and Annealed Germanium Surfaces
Authors: Wienskowski J. V. , Mönch W. 
Published: July 2007

AbstractThe channel conductivity of clean germanium surfaces cleaved in ultrahigh vacuum has been measured for 10 Ωcm n‐type bulk resistivity. Immediately after cleavage the surface conductivity is found to be 2.8 × 10−4 Ω−1 ± 50%. The corresponding surface potential is evaluated to (EF − Ei)s = −(0.387 ± 0.04) eV, i.e. the valence band edge coincides with the Fermi level at the surface. A lower limit of the surface state density is estimated to 1 × 1013 cm−2. Upon annealing the cleaved surface at 420°K the surface conductivity decreases by about 70%. The surface potential is thus lowered to (EF − Ei)s = −(0.292 ± 0.05) eV. The surface state density then amounts at least to 2 × 1012 cm−2.
Galvanomagnetic Coefficients for p‐Type Lead Telluride
Authors: Gupta S. C. , Sreedhar A. K. 
Published: July 2007

AbstractThe longitudinal and transverse components of the magnetoconductivity tensor have been calculated for degenerate p‐type lead telluride for the parabolic and non‐parabolic, non‐ellipsoidal band models. The results obtained on the basis of these two models are compared for acoustic, optical, and impurity scattering mechanisms assuming a scalar isotropic relaxation time. It is shown that the importance of acoustic scattering increases relative to optical scattering when the bands become non‐parabolic and energy surfaces non‐ellipsoidal.
Spin Fluctuations in Co0.5Zn0.5Fe2O4 Using the Mössbauer Effect
Authors: Iyengar P. K. , Bhargava S. C. 
Published: July 2007

AbstractMössbauer measurements in Co0.5Zn0.5Fe2O4 with 14.4 keV γ‐rays from Fe57 are reported. The spectra, in the temperature range from 90 to 455 °K, show features characteristic of relaxation effects. The shape of the spectra is related to the dynamical properties of the spins using a stochastic model for spin fluctuations. The overall agreement of the experimental data with computed shapes is satisfactory. There is no significant change in the value of relaxation time in the temperature range between 90 and 387 °K, and the change in the shape of the spectrum is mainly due to an increase in the value of s (the spin population parameter), and a decrease in the value of δ. A significant difference in the transition temperatures, as determined by neutron diffraction and the Mössbauer effect, can be explained to be due to the effect of relaxation on the shape of the Mössbauer spectrum. The presence of the relaxation effect is attributed to the influence of Zn2+ ions.
Lifetimes of Parity Forbidden Transitions of the Cu+ Center in the Alkali Iodides
Authors: Mack S. A. , van Sciver W. J. 
Published: July 2007

AbstractThe ultraviolet photoluminescence spectra and excited state lifetime measurements of the Cu+ center in the alkali iodides are reported from 5 to 300 °K. The long lifetimes (greater than 10 μs for all temperatures) obtained indicate that a forbidden transition is involved. The strong temperature dependence of the emission lifetime for LiI:Cu and NaI:Cu is explained on the basis of a linear electron–phonon interaction coupling even and odd parity states, whereas the weak temperature dependence and shorter lifetimes observed for KI:Cu and RbI:Cu are explained on the basis of an off‐center position for the Cu+ excited ion. The oscillator strength determination for the Cu+ absorption in RbI:Cu and the temperature dependence of the absorption for LiI:Cu are reported. These measurements and similar measurements by other authors on NaI:Cu and KI:Cu are compared with the lifetime data. The absence of a correlation between lifetime and absorption measurements indicates that the levels involved in the emission process are different from those of the absorption process.
Parelektrische Resonanz von Li+ in KCl Messungen im E‐Band und Unter Einachsigem Druck
Authors: Blumenstock D. , Osswald R. , Wolf H. C. 
Published: July 2007

AbstractParelektrische Resonanz (PER) an Li+ in KCl wurde bei verschiedenen Frequenzen zwischen 60 und 75 GHz, sowie unter einachsigem Druck bei 35 GHz beobachtet. Die Messungen wurden für drei Orientierungen des statischen elektrischen Feldes Eo und des Drucks P bezüglich der Kristallachsen durchgeführt. Sie stützen das kürzlich [1] vorgeschlagene Modell und können mit folgenden Parametern erklärt werden: Das elektrische Dipolmoment |P| = (6,0 ± 0,3) Debye zeigt in eine [111]‐Richtung. Eine Tunnelbewegung des Li+ ist längs der [100] und der [110]‐Achsen möglich.Die zugehörigen Matrixelemente sind: |K| = (11,6 ± 0,2) GHz und |F| = (3,2 ± 0,2) GHz. Für die Differenz der Hauptwerte des elastischen Dipoltensors ergibt sich: λ1 – λ2 = (6 ± 2) × 10−3.
Quantum Statistics of Ionization and Shielding Effects in Non‐Degenerate Moderately Doped Semiconductors
Authors: Ebeling W. 
Published: July 2007

AbstractIn the framework of the hydrogen plasma model the semiconductor is considered as a system of donors and electrons in a uniform medium. A recently developed quantum‐statistical theory of hydrogen plasmas in thermal equilibrium is applied to this simple model; the lowering of the activation energy is calculated exactly up to the order O(n) where n is the electron density. Especially the influence of shielding effects on the activation energy is studied. A method for the treatment of partly compensated semiconductors is proposed. Explicit results are given for the degree of ionization in n‐type Ge as a function of the donor concentration and the temperatures. The limits of the stability region with respect to ambipolar diffusion are diseussed.
Phonon Structure in the Luminescence of Sm++ Doped KClxBr1–x and KxRb1–x alloys
Authors: Baldini G. , Guzzi M. 
Published: July 2007

AbstractSm++ ions diluted in alkali halide alloys are employed in order to determine the crystal phonon density of states at low temperature and to probe the degree of configurational disorder in the matrices.
New Type of Ferroelectric Soft Mode in Gadolinium Molybdate
Authors: Petzelt J. , Dvořák V. 
Published: July 2007

AbstractA group analysis is made of external lattice vibrations in Gd2(MoO4)3 for k = (1, 1, 0) in the high‐symmetry D phase and for the Γ‐point in the low‐symmetry C phase. It is shown that the phase transition is induced by an instability of one double degenerate T1‐phonon at the M‐point of the Brillouin zone which changes into two A1‐phonons, infrared and Raman active below the phase transition. The far‐infrared reflectivity and transmission measurements show that these critical modes are extremely weak and lie at 45 and 56 cm−1 at −150 °C. When rising the temperature they become indistinct and probably disappear above the phase transition. This behaviour together with known dielectric and Raman scattering experiments is discussed in terms of the recent theory of the soft‐mode behaviour in improper ferroelectrics.