bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Theory of Transport Phenomena in Low Mobility Crystals (I)
Authors: Klinger M. I.
Published: July 2007

Previous theory [9] is developed to give a simple and sufficient general method of calculating transport coefficients in low mobility solids. The current is considered to be carried either by small polarons or by such type carriers (in the condon type cases [4]). Formulae for the mobility tensor and thermoelectric coefficients are derived and discussed.
Photon‐Induced Reorientation of M‐Centers in Potassium Chloride
Authors: Turner T. J. , De Batist R. , Haven Y.
Published: July 2007

The reorientation of M‐centers in additively colored KCl crystals, due to the absorption of polarized F‐light is studied experimentally. The time dependence of the resulting dichroism can be described by either one, or two relaxation times, depending upon the geometry. This agrees with the theoretical predictions of a previous paper [21]. From the values of the relaxation times obtained at 200 °K, it is concluded that absorption of MF [001] photons induces a rotation of the M‐center with a quantum efficiency which is approximately three times as large as that associated with absorption of MF [011] photons. The temperature dependence of the quantum efficiency for the process can be described by an activation energy of a few hundredths of an eV.
Tracer Diffusion in β‐Titanium
Authors: Askill J. , Gibbs G. B.
Published: July 2007

Tracer diffusion measurements in β‐titanium are reviewed and new data presented for solutes Sc46, Sn113, and P32. All Arrhenius plots are curved and give unusually low activation energies and frequency factors. Various explanations are outlined and it is suggested that monovacancy diffusion dominates but that divacancy contributions may become appreciable near the melting point. Impurity activation energies and diffusion rates are closely related to atomic size and compressibility.
Volumenselbstdiffusion in polykristallinem Antimon
Authors: Hässner A. , Hässner R.
Published: July 2007

Die Volumenselbstdiffusion in polykristallinem Antimon wurde im Temperaturbereich 384 bis 583 °C mit der Restaktivitätsmethode untersucht. Zwischen 473 und 583 °C kann die Temperaturabhängigkeit des SDK durch folgende Parameter charakterisiert werden: D0 = 1,05 cm2/s, Q = (39,5 ± 1,4) kcal/mol. Die Werte stimmen im wesentlichen mit Angaben von Huntington und Mitarbeitern überein. In der Diskussion wird das anomale Selbstdiffusionsverhalten von Antimon sowie anderer Elemente der Klassen II und III behandelt.
Effects of Dilute Rare‐Earth Additions on the Electrical Conductivity of Cerium at Low Temperatures
Authors: Clinard F. W. , Elliott R. O. , Miner W. N.
Published: July 2007

Two atomic percent of the various trivalent rare earths were dissolved in cerium, and the electrical resistivities of these dilute binary alloys evaluated in the range 1.5 to 297 °K in order to determine whether the various solute magnetic properties might be reflected in resistivity measurements. The γ and β‐cerium phases at room temperature showed a roughly linear dependence of resistivity on atomic number of the rare‐earth solute, noted was a slight effect attributed to solvent‐solute atomic size mismatch. At 4 °K the resistivities of predominantly α phases were found to be influenced by small amounts of β, and predominantly β phases by small amounts of α. Spin‐disorder resistivities for the β phase of the various alloys did not reflect the influence of any solute magnetic parameters, but did decrease slightly in the direction of the heavier rare‐earth solutes.
Magnetic After‐Effects in Iron‐Rich Ferrites Containing Vacancies
Authors: Braginski A.
Published: July 2007

Three ionic‐migration magnetic after‐effects are considered on the basis of a Fe2+‐ion anisotropy model. These effects occur in magnetite, and in iron‐rich ferrites containing vacancies. A brief survey of experimental data is given. Results are quoted for temperature spectra of disaccommodation, domain‐wall stabilization in polycrystalline samples, and induced anisotropy relaxation in single crystals. All three effects can be ascribed, by using Slonczewski's theory, to the Fe2+ anisotropic interaction with the spontaneous magnetization in a spinel lattice. It is believed that this interaction causes migration of single Fe2+‐ions, and of Fe2+ — Fe2+ pairs, through intermediary single vacancies. Satisfactory qualitative agreement is found between the experimental results and the proposed model.
Electronic Attenuation of Longitudinal Soundwaves in Aluminium
Authors: Berre B. , Olsen T.
Published: July 2007

The frequency dependence of the difference between the attenuation of longitudinal soundwaves in a perpendicular magnetic field and in zero field is used in an experimental analysis of three parameters in the electron‐phonon interaction. The parameters are the electron mean free path and the magnitude of the interaction in zero and infinite field. The first parameter is compared with the mean free path deduced from electrical size effects. The interaction parameter in zero field is found to be in fair agreement with theoretical estimates. In high fields the interaction is not localized at the fermi surface, and it is found that symmetrically shaped orbits having an electron group velocity normal to the magnetic field, contribute most strongly to the attenuation.
The Determination of the Bond Energies in the Alloy System Au‐Cu
Authors: Zsoldos L.
Published: July 2007

The various bond energies are calculated from the heats of formation, using the basic assumption that the energies vary quadratically with small variations of the nearest‐neighbour distance. The ordering‐energies in AuCu3 and Au3Cu alloys are found to be 0.0486 and 0.0396 eV, respectively.
The Theoretical Elastic Constants and Specific Heats of Rutile
Authors: Pandey H. N.
Published: July 2007

The Raman and infrared spectra of rutile are analysed. The force constants are calculated using the Narayanan and Krishnamurti assignment of the Raman frequencies and one of the infrared frequencies. Elastic constants and specific heats are also calculated and agreement found with experimental results.
Energieänderung der Leitungselektronen durch Punktfehler in Metallen. I. Allgemeine Theorie
Authors: Mann E.
Published: July 2007

In der Schrödingergleichung für einen durch atomare Gitterfehler gestörten Kristall wird in einer Einelektronennäherung die Wellenfunktion nach Wannier‐Funktionen entwickelt. Die Differenzengleichungen für die Entwicklungskoeffizienten enthalten das im Falle der Metalle lokalisierte Störpotential nur in Form weniger Matrixelemente. Sowohl die Elektronenstruktur des ungestörten Kristalls als auch die Struktur der Störung sind im Prinzip voll erfaßbar. Durch die Formulierung mittels Greenscher Funktionen ergibt sich ein Gleichungssystem, dessen Determinante effektiv nur von geringer Ordnung ist. Ausgehend von der Konzeption diskreter Eigenwerte wird gezeigt, wie hieraus die Energieänderung der Elektronen zu berechnen ist; dafür werden zwei Methoden angegeben. Mit einer der Methoden können auch die Eigenfunktionen zu geänderten Energieeigenwerten berechnet werden (als stehende Wellen). Durch Symmetriebetrachtungen ist es in der Regel möglich, das Gesamtproblem auf einfachere Probleme zurückzuführen.
Paramagnetische Resonanz des Mn++ in S‐ oder Se‐haltigen Silberhalogeniden
Authors: Hennig K.
Published: July 2007

Es werden bei 20, 90 und 300 °K gemessene Elektronenresonanzspektren des Mn++ in zusätzlich mit Chalkogenionen dotierten Silberhalogeniden diskutiert. Falls die Chalkogenionenkonzentration größer als die Mn‐Konzentration ist, treten zwei Spektren auf, die isoliertem Mn++ auf Silberionenplatz und dem Assoziat des Mn++ auf Silberionenplatz mit S−‐ auf dem unmittelbar benachbarten Bromionenplatz zugeordnet werden können. Dabei war das in nur mit Mn++ dotierten Silberhalogeniden bei 90 °K allein auftretende Assoziat zwischen Mn++ und der Silberionenlücke nicht nachweisbar.
Das Reflexionsvermögen von Germanium‐ und Silizium‐Einkristallen bei elastischer Deformation
Authors: Gerhardt U.
Published: July 2007

Das Reflexionsvermögen von uniaxial in [001]‐ und [111]‐Richtung verformtem Ge und Si (Verformung ≈ 0,4%) wird mit linear polarisiertem Licht gemessen. Untersucht werden die Reflexionsmaxima des Ge bei 2 und 4,5 eV und die des Si bei 3,4 und 4,5 eV. Die durch die Verformung hervorgerufenen Änderungen des Reflexionsvermögens (ΔR ≈ 1%) rühren überwiegend von Änderungen der Übergangsmatrixelemente her, die wegen der Symmetrieerniedrigung auftreten. Die beobachteten Energieverschiebungen der Maxima (ΔE ≈ ≈ 10 meV) kommen durch Verschiebungen der Energiebänder zustande. Aus diesen Energieverschiebungen werden einige Deformationspotentiale bestimmt.
Work Hardening and Thermally Activated Flow in Magnesium Single Crystals
Authors: Sharp J. V. , Christian J. W.
Published: July 2007

Shear stress vs. shear strain curves have been obtained from magnesium single crystals orientated for basal glide and tested in tension over the temperature range 77 to 413 °K. Incremental changes of strain rate and temperature were also made and the results used to deduce the usual parameters of thermally activated flow. A two‐stage hardening curve was found, the work‐hardening rate being 150 to 400 g/mm2 in stage I at room temperature, and 3 to 5 kg/mm2 in stage II. The Cottrell‐Stokes law was found to be obeyed for strain rate changes at low temperatures, but at higher temperatures the behaviour was more complex. The activation energy for stage I deformation increased to a roughly constant value of 0.3 to 0.4 eV at high temperatures.
Dislocation Structure in Deformed Single Crystals of Magnesium
Authors: Sharp J. V. , Makin M. J. , Christian J. W.
Published: July 2007

The dislocation structure produced by tensile deformation of magnesium single crystals at 77 K and at room temperature has been investigated by transmission electron microscopy techniques. Sections both parallel and perpendicular to the basal plane have been cut by spark machining from single crystals deformed into both stages of the hardening curve. In stage I, edge dipoles and braids consisting of edge dislocations and dipoles are the prominent features, and the low density of screw dislocations suggests that annihilation has occurred. Very few dislocations with non‐basal Burgers vectors have been observed and the density of forest dislocations is less than 107 cm−2 unless dislocations have been lost from the foils. There is no evidence for slip on non‐basal slip systems even at the highest deformation examined (0.8 shear). In the early stages of deformation large clear areas are seen between braids. As deformation proceeds the local spacing between braids decreases and in stage II the areas between braids become filled with dislocations. After deformation at 77 K the dislocation density is more uniform. Twinning was the only new feature found in crystals deformed into stage II. The formation of the braids and dipoles is discussed and strain hardening is considered in terms of the observed dislocation structure. The flow stress in stage I is believed to be determined by the number of excess dislocations of one sign present in the braids, and the stability of the braids is probably due to short edge dipoles which have been swept into them.
Untersuchung einiger thermischer Eigenschaften der Verbindungen HgSe, HgTe und ZnTe
Authors: Kelemen F. , Cruceanu E. , Niculescu D.
Published: July 2007

Es wurden die thermischen Eigenschaften (Temperaturleitzahl, spezifische Wärme und Wärmeleitung) des ZnTe, HgTe und HgSe, bei Temperaturen von 20 bis 540 °C für ZnTe und von 20 bis 240 °C für HgTe und HgSe untersucht. Die Messungen wurden an Einkristallen ausgeführt, die nach dem Bridgman‐Verfahren aus hochgereinigten Elementen hergestellt worden waren.

Die Analyse der Temperaturänderung der Gitterwärmeleitfähigkeit zeigte, daß sie im Falle des ZnTe durch Umklapp‐Prozesse zu erklären sind dagegen muß bei HgTe und HgSe auch die Streuung der akustischen Phononen an den optischen Phononen und den Stromträgern in Betracht gezogen werden.
Temperature Dependence of the Spectrum of the Photoluminescence in CdSe Crystals
Authors: Wojtowicz‐Natanson B. , Zakrzewski T.
Published: July 2007

An investigation is made of the temperature dependence of the intensity and spectral distribution of the luminescence due to the recombination of excitons in CdSe crystals. The measurements are made at temperatures between 300 and 4.2 °K. It is suggested that complexes, formed from excitons bound to ionized acceptors, play an essential part in emission.
Structure of Exciton Bands in Crystalline Anthracene
Authors: Davydov A. S. , Sheka E. F.
Published: July 2007

An investigation is made of the dependence of the exciton energy, in an anthracene crystal, on the magnitude and direction of the quasi‐momentum in the two energy bands which correspond to the first electron excitation of the molecule. It is shown that the exciton band width, the exciton effective mass, and the magnitude of the “resonance splitting”, depend only on the direction of the quasi‐momentum but also on the dimension of the region where the interaction between the molecules occurs. The theory predicts a polarization of the exciton doublets and gives their position for the various directions of the exciton wave‐vector. From a comparison of theoretical and experimental values for the resonance splitting the radius of the effective molecular resonance interaction in the anthracene crystal is established to be of the order of 0.05 μm.
Effect of Oxygen on Some Electrical Properties of Selenium
Authors: Abdullaev G. B. , Mekhtieva S. I. , Sh. Abdinov D. , Aliev G. M.
Published: July 2007

It is established several, previously obscure, properties of selenium are due to the presence of oxygen and to oxygen complex formation. The properties include the appearance of an extremum in the curves of the concentration dependence of electroconductivity (σ), thermoelectromotive force (θ), thermal conductivity (λ), density (Q), mechanical strength, activation energy during self diffusion (λE), and microhardness (H). Other properties are the shift of the second maximum in the photoconductivity curve during the introduction of different admixtures, the decrease of σ and θ during melting, and the instability of the parameters of selenium instruments.
Incorporation of Cd‐Interstitial Double Donors into CdS Single Crystals
Authors: Boyn R. , Goede O. , Kuschnerus S.
Published: July 2007

The incorporation of excess Cd into CdS crystals in a Cd atmosphere is studied experimentally. During the heat treatment in Cd vapour the conductivity (ν) of the crystals is measured as a function of Cd pressure (pCd) and temperature, between 400 and 730 °C. The relaxation of σ after a step‐like increase in pCd is also investigated. It is shown that excess Cd is incorporated in the form of doubly ionised Cd interstitials (Cd○2+), and this leads to a transition from “pure” Frenkel disorder to interstitial disorder. The energy required for the incorporation of a neutral Cd atom on an interstitial site (Cdgas → Cd), the migration energy of Cd, and the first ionisation energy of Cd○ are found to be 1.0 eV, 0.62 eV, and 0.05 eV, respectively. The formation energy of a Frenkel defect (Cd + Cd) is estimated to be about 2.5 eV. The temperature dependence of the conductivity of crystals quenched after heat treatment in Cd vapour is also measured and is found to be determined by the first ionisation of Cd○ at low temperatures. It is shown that large concentrations of Cd interstitials and Cd vacancies can be frozen in by quenching.
Zum Problem der Lebensdauermessung mit der Doppelimpulsmethode bei Silizium‐Einkristallen
Authors: Lemke H.
Published: July 2007

Für Lebensdauermessungen an reinen Silizium‐Einkristallen wird ein Impulsverfahren unter Verwendung injizierender Metall‐Halbleiterkontakte beschrieben. Mit der Methode können insbesondere bei p‐Silizium Lebensdauerwerte im Bereich von 10−6 bis 10−3 s bei spezifischen Widerständen ≳ 1 Ωcm gemessen werden. Der Abklingverlauf der injizierten Minoritätsträgerkonzentration kann durch Modulation der Impulsverzögerung oszillographisch geschrieben werden. Die aus den Abklingfunktionen ermittelten Lebensdauern stimmen innerhalb von 20% mit den aus Messungen der nichtstationären Photoleitung bestimmten Werten überein. Die Orts‐ und Zeitabhängigkeit der Minoritätsträgerkonzentration wird für schwache Injektion berechnet.
Spiralversetzungen in dampfphasengezüchteten CdS‐Kristallen
Authors: Möhling W. , Peibst H.
Published: July 2007

Es werden Überlegungen über den Entstehungsmechanismus von Spiralversetzungen in reinen, nach Frerichs gezüchteten CdS‐Kristallen angestellt.
PME‐Messungen zur Untersuchung der Rekombinationseigenschaften von InSb
Authors: Richter G.
Published: July 2007

Die Rekombination von Nichtgleichgewichtsladungsträgern in p‐Typ‐Indiumantimonid wird mit dem stationären photomagnetoelektrischen Effekt untersucht. Zur Beschreibung der Experimente bewährt sich im untersuchten Temperaturintervall das Modell von Shockley und Read mit einem einfachen Rekombinationszentrum.
Kinetics of the Monopolar Conductivity in the Space Charge Region, in a Non‐Equilibrium State of the Semiconductor Volume
Authors: Litovchenko V. G. , Gorban A. P. , Kovbasyuk V. P.
Published: July 2007

Investigations of kinetic space charge monopolar photoconductivity during illumination are performed as for n‐ and p‐type silicon. In particular, some complex cases are studied (existence of photocarrier surface traps, diffusion redistribution of photocarriers etc.) The experimental data are in a good agreement with theoretical relation obtained with some simplifying assumptions. A series of nomograms are presented which are convenient for determining both the initial bending of the bands and the trap energies.
The Phonon Drag in Ionic Semiconductors
Authors: Plâviţu C. N.
Published: July 2007

The acoustic and optical phonon drag is considered for the case of a pure ionic n‐type semiconductor. The evaluation of some kinetic coefficients shows that the contribution of the optical phonon drag may be significant both at high and at low temperatures.
The Precipitation Behaviour of Copper in Silicon Single Crystals
Authors: Fiermans L. , Vennik J.
Published: July 2007

The precipitation behaviour of copper in silicon is examined from a macroscopic point of view by means of I.R. microscopy, X‐ray micrography, and etching. It is shown that the arms of the starts and the “needles” commonly observed in silicon which is heavily decorated with copper, have the form of “swords” parallel to the (111) and pointing in the 〈110〉 directions. These sword‐like regions are built up of a large number of small copper containing specks and dislocations. A mechanism is proposed which explains the nucleation and growth of the decoration‐patterns. This is based on indentation by oxygen containing precipitates and climb of the resulting fresh dislocation. The X‐ray experiments show that, although decorated dislocations produce a broadened image and complete extinction cannot be obtained, the determination of the Burgers vector is still possible.
Etude radiocristallographique des fautes d'empilement dans les alliages cubiques à faces centrées du nickel
Authors: Clement A. , Coulomb P.
Published: July 2007

Nous avons étudié par la méthode de Paterson la probabilité de faute d'empilement dans une série d'alliages de nickel limés dans l'azote liquide et maintenus à −150 °C pendant la diffraction des rayons X. Le titane, le silicium et le molybdène élèvent considérablement la probabilité de faute, même lorsque leur teneur est faible; l'effet du chrome n'est considérable que grâce à son importante solubilité dans le nickel. Ces résultats corroborent les textures de laminage trouvées dans la bibliographie.
Optical Modulation of Current in GeSi n—n Heterojunctions
Authors: Yawata S. , Anderson R. L.
Published: July 2007

The I–V, characteristics, the C—V characteristics and the photocurrent spectra of GeSi n—n heterojunctions are consistent with a model in which a depletion region exists in each material. The depleted electrons reside in interface states which result from the mis‐match in lattice constants of the two materials. In this model, a notch exists in the valence band edge profile. Optically generated holes are trapped in the notch and the trapped holes modulate the device. The quantum efficiency of such a device compares favorably with that of a Si p—n homojunction.
Phonon Dispersion in α‐Iron
Authors: Gupta R. P. , Sharma P. K.
Published: July 2007

The phonon dispersion curves are calculated for lattice waves along the three symmetry directions [100], [110], and [111] in α‐iron. The calculation use the three‐force‐constant model for cubic metals propounded by Sharma. The calculated dispersion curves are compared with the experimental curves of Low obtained by neutron spectrometry and reasonably good agreement found.
Phonon Drag Effect in p‐Type InSb
Authors: Byszewski P. , Gronkowska M. , Kołodziejczak J.
Published: July 2007

The thermoelectric power is measured as a function of temperature for three samples of p‐type InSb. At low temperatures the phonon drag effect is observed. The phonon drag contribution to the thermoelectric power is found be proportional to T−2.9.
Stress Dichroism and Paraelasticity of OH‐Molecules in KCl
Authors: Härtel H. , Lüty F.
Published: July 2007

Paraelastic alignment following a Curie law is observed for OH− molecules in KCl and measured quantitatively by stress‐induced dichroism. The dependence on stress direction confirms a model of [100] oriented dipoles. Using results from lattice parameter measurements the components of the tetragonal elastic dipole can be evaluated.
Über den Einfluß der Bestrahlung mit geringen Röntgendosen auf die Verfärbbarkeit von CKl‐Kristallen durch F‐Zentren
Authors: Fröhlich F. , Grau P.
Published: July 2007

Durch wiederholte kurzzeitige Röntgenbestrahlung geringer Intensität und Bleichung mit weißem Licht läßt sich in KCl‐Kristallen eine beträchtliche Erhöhung der Verfärbbarkeit durch F‐Zentren im Anfangsverlauf der Bildungskurve erreichen. Die dafür verantwortlichen Defekte können thermisch über zwei Stufen mit Aktivierungsenergien von 0,68 eV bzw. 0,9 eV bis 1,0 eV ausgeheilt werden. Der Anteil der beiden Stufen hängt von der Vorgeschichte der Proben ab. Die wirksamen Defekte sind mit OH‐Ionenverunreinigungen verbunden, die wahrscheinlich über U‐Zentren zu einer Vergrößerung der Bildungsgeschwindigkeit von F‐Zentren und über die von ihnen verstärkte Kolloidbildung zu einer Erhöhung der nachweisbaren Anionenleerstellenkonzentration führen.
Die spezifische Wärme von Eisen, Kobalt und Nickel im Bereich hoher Temperaturen
Authors: Braun M. , Kohlhaas R.
Published: July 2007

Die spezifische Wärme von Eisen, Kobalt und Nickel wurde mit einem neuen, unter Schutzgas betriebenen, quasiadiabatisch arbeitenden Kalorimeter im Bereich von Raumtemperatur bis jeweils dicht unterhalb des Schmelzpunktes gemessen. Mit den Meßergebnissen für Eisen werden zunächst die thermodynamischen Funktionen der beiden Eisenmodifikationen im Bereich der γ‐Phase neu bestimmt. Dann wird der Gesamtbetrag der spezifischen Wärme der drei Metalle näherungsweise in seine Anteile zerlegt. Es gelingt, den magnetischen Anteil zur spezifischen Wärme infolge der starken Anomalie am Curiepunkt quantitativ vom gemessenen Temperaturverlauf abzuspalten, so daß ein Vergleich mit dem theoretisch erwarteten Verlauf möglich ist.
Optische Untersuchungen zur Wasserdampfsorption in Aufdampfschichten (insbesondere in MgF2‐Schichten)
Authors: Koch H.
Published: July 2007

An MgF2‐, Kryolith‐, SiO‐ und ZnS‐Schichten der optischen Dicke ns ds ≈ 500 nm, die als Abstandsschichten eines Fabry‐Perot‐Interferenzfiltersystems zwischen Silberschichten eingebettet waren, wurde die Sorption von Wasserdampf mit der Methode der „fringes of equal chromatic order”︁ näher untersucht. In besonders starkem Maße wird Wasserdampf durch MgF2‐Schichten sorbiert. Die Wasserdampfsorption durch MgF2‐Schichten ist nur zum Teil reversibel. Ein Teil des Wasserdampfes wird durch Chemisorption irreversible gebunden. Für die besonders eingehend untersuchten MgF2‐Schichten wird ein einfaches Modell für die Schichtstruktur benutzt, um die experimentellen Ergebnisse zu deuten. Mit Hilfe dieser Modellvorstellung (in der angenommen wird, daß die MgF2‐Schichten aus kugelförmigen Aggregaten in dichter Packung aufgebaut sind) ist es möglich, über den irreversibel chemisorbierten Wasserdampfanteil Kristallitgrößen von ca. 100 bis 200 Å Durchmesser abzuschätzen. Die im Vergleich zu den anderen untersuchten Substanzen besonders ausgeprägte Fähigkeit der MgF2‐Schichten, Wasserdampf sorbieren zu können, ist vermutlich auf die hohe Polarität der MgF2‐Valenzbindungen und nicht auf eine wesentlich stärkere Lockerstruktur der MgF2‐Schichten zurückzuführen.
Untersuchung der chlorinduzierten optischen Absorption des Silberchlorids
Authors: Ulrici W. , Koswig H. D. , Stasiw O.
Published: July 2007

Es wurde die durch eine äußere Chloratmosphäre in AgCl‐Kristallen bei einer Temperatur oberhalb 200 °C auftretende optische Absorption untersucht und als Absorption freier Defektelektronen gedeutet. Aus dem zeitlichen Verhalten beim Auf‐ und Abbau dieser Absorption können scheinbare Defektelektronenbeweglichkeiten ermittelt werden.
Die Diffusion und der Isotopeneffekt von Na22 und Na24 in Silberchlorid
Authors: Süptitz P.
Published: July 2007

Der Wanderungsmechanismus von Na+‐Ionen im AgCl wird durch Messung des Diffusionskoeffizienten in Abhängigkeit von der Temperatur (180 bis 450 °C) und der Dotierung (Na, Cd) sowie durch Messung des Isotopeneffektes (Na22 und Na24) aufgeklärt. Für die Temperaturabhängigkeit wurde gefunden

wobei oberhalb 300 °C D stärker anwächst. Durch Na+‐Dotierung wird D kaum beeinflußt, durch Cd++‐Dotierung dagegen stark. Dies ist nur mit der Annahme eines Lückenmechanismus erklärbar. Die Größe der Na‐Diffusion wird als Maß für die Konzentration der Kationenlücken verwendet. Bei den Cd‐dotierten Kristallen wird die Assoziation der Lücken mit den Cd++‐Ionen berechnet, bei den undotierten Kristallen wird das starke Anwachsen von D bei hohen Temperaturen auf ein anomal starkes Wachsen der Frenkelfehlordnung zurückgeführt. — Die Isotopeneffekt‐Methode erweist sich zur Aufklärung des Wanderungsmechanismus in diesem Fall weniger aussagekräftig, da der ermittelte Wert für

nicht allein im Fall des Lückenmechanismus erwartet wird.
Photoimpedanzmessungen und Raumladungsprozesse in Photoleitern vom CdS‐Typ
Authors: Krispin P. , Ludwig W.
Published: July 2007

Kapazität und dielektrischer Verlustfaktor von Einkristallen vom CdS‐Typ, die entweder mit Polystyrolfolien bedeckt oder mit SiO‐Schichten im Vakuum bedampft wurden, werden in Abhängigkeit von der Frequenz des angelegten Wechselfeldes und der Anregungsintensität gemessen. Die Frequenzabhängigkeit der Meßgrößen kann formal mit den Debye‐Gleichungen beschrieben werden. Das Impedanzverhalten obiger Anordnung wird befriedigend mit der Vorstellung einer Raumladungsschicht an den blockierenden Elektroden erklärt. Zur Berechnung der komplexen Kapazität wird ein reaktionskinetisches Modell nach Böer und Voigt und die lineare Theorie der Raumladungspolarisation von Macdonald benutzt. Allgemein treten zwei Dispersionsgebiete auf, die von der endlichen Beweglichkeit und Lebensdauer der Ladungsträger im Leitungsband herrühren.
Magnetic and Electrical Properties of NdNbO4 and GdNbO4
Authors: Wang F. F. Y. , Gravel R. L.
Published: July 2007

Polycrystalline NdNbO4 and GdNbO4, isostructural with the monoclinic form of YTaO4 (Fergusonite), were prepared by the usual ceramic method. GdNbO4 is paramagnetic with an asymptotic Curie point extrapolated to be 0 °K. NdNbO4 becomes antiferromagetic at 25 °K. Their room temperature electrical resistivities are very high, in the neighborhood of 1011 to 1012 Ωcm. The activation energy for the conduction process is 0.92 eV and 1.08 eV with respect to NdNbO4 and GdNbO4, respectively. The electrical conduction is n‐type in both cases. Both compounds show a dielectric constant maximum, measured at 1 kHz. The transition temperature is 1080 °K and 1030 °K for NdNbO4 and GdNbO4, respectively.
Correlation Corrections for Nuclear Magnetic Resonance Studies of Diffusion
Authors: Stoebe T. G. , Ogurtani T. O. , Huggins R. A.
Published: July 2007

Correlation corrections for diffusion coefficients which are measured using the technique of motional narrowing of nuclear magnetic resonance lines are considered. The results are applied to vacancy diffusion in alkali halide crystals, and previous work is clarified and extended to the consideration of associated vacancies. Relative values of diffusivity and activation energy are determined in the associated vacancy extrinsic region for NMR, radioactive tracer, and ionic conductivity methods of determination, and the relevant correlation corrections are derived.
Spin‐Magnetophonon Resonance in Semiconductors
Authors: Tsidilkovskii I. M. , Akselrod M. M. , Uritsky S. I.
Published: July 2007

A theory is presented for spin‐magnetophonon resonance. The spin interaction of electrons with optical phonons is described by the introduction of vector and scalar potentials of the optical vibrational field. It is shown that the spin‐magnetophonon resonance should cause a minimum in the longitudinal magnetoresistance. The experimental data for n‐InSb and n‐InAs are discussed on the basis of this theory. Certain new magnetoresistance measurements are presented for the case of n‐InSb: 1) A maximum of the transverse magnetoresistance is observed at 82 kG corresponding to the spin‐magnetophonon resonance. The g‐factor for the conduction electrons, calculated from this maximum, is in good agreement with the theoretical value. 2) A minimum in the longitudinal magnetoresistance is observed at 24 kG, dur to the combined magnetophonon and spin‐magnetophonon resonance scattering.
Der Wärmewiderstand von Kristallen infolge kombinierter Streuung von Phononen and Phononen und an Fehlstellen
Authors: Gruner P.
Published: July 2007

Mit Hilfe der nichtlinearen Elastizitätstheorie wird der thermische Widerstand bei tiefen Temperaturen infolge der Streuung der Phononen an Phononen und an Gitterfehlern untersucht. Es wird gezeigt, daß die bei der Streuung von langwelligen Gitterschwingungen an Punktfehlern auftretenden Divergenzen in der Wärmeleitfähigkeit χ durch Hinzunahme der Dreiphononenwechselwirkung vermieden. χ verhält sich in diesem Fall bei Temperaturen in der Gegend des flüssigen Heliums wie T−1 und fällt nach hohen Temperaturen hin wie T−α ab (1 < α < 2). Durch zusätzliche Streuung der Gitterwellen an Versetzungen wird diese Temperaturabhängigkeit der Wärmeleitfähigkeit völlig verändert. Bei tiefen Temperaturen ist χ proportional zu T2, durchläuft mit zunehmender Temperatur ein Maximum, um dann nach hohen Temperaturen hin wieder wie T−α abzufallen.
The Effect of s‐p Hybridization on the Band Structure of a Perturbed Linear Chain
Authors: Mourad P.
Published: July 2007

The LCAO approximation is used to study the effects of s‐p hybridization on the band structure of a linear chain in the presence of a localized perturbation. Bound states normally appear at the centre and at the edge of the Brillouin zone; but sometimes hybridization will introduce an intermediary minimum in the band structure and a perturbation will make a bound state leave the band at the minimum. The symmetries of the bound states are examined. The hybrid character of the self‐trapped hole in the VK centre is analysed in this way.
Dislocation Damping of Zone Refined Aluminium Doped with Cu
Authors: Gelli D.
Published: July 2007

Internal friction measurements are made at frequencies of a few kHz on well annealed aluminium containing a few p.p.m. of Cu. The results agree with the dislocation damping model [20] which is based on specific assumptions regarding the impurity atmosphere around dislocations. A linearly increasing component is found at the lowest amplitudes which is additional to the parabolic and Granato‐Lücke components previously found. The method of analysing the results, and calculating the parameters, which control the amplitude dependence of the i.f., are defined in detail. A new hypothesis is discussed regarding the shape of the potential valley connected with the dislocation—atmosphere elastic interaction.
Useful Properties of Dark‐Field Electron Images
Authors: Bell W. L. , Thomas G.
Published: July 2007

Tilting experiments in dark‐field under s ≠ 0 conditions have shown that the image contrast is greatest at the top and bottom surfaces of a foil for s < 0 and s > 0, respectively. This effect has been shown for images of stacking faults or slip traces, inclined dislocations, prismatic loops, precipitates, and small defects observable by strain contrast. This asymmetry is observed only where anomalous absorption is an important factor in controlling the image intensity. The effect can be utilized for obtaining the unique foil orientation without using complicated procedures, such as wedge tilting or X‐ray analysis of the foil in the specimen holder. Once the unique orientation is found, a complete analysis of lattice defects can be carried out with a maximum of two dark‐field photographs. The approximate position of a defect within the foil can also be determined.
The Effect of Solute Concentration on the Formation of Loops in Aluminium‐Magnesium Alloys during Fission Fragment Irradiation
Authors: Vigeholm B. , Makin M. J.
Published: July 2007

A study has been made of the effect of magnesium concentration (up to 0.5 at%) on the formation of dislocation loops in aluminium during fission fragment bombardment at 60 °C. Increasing magnesium content reduces the initial rate of increase of the total loop area with dose, but the loop area saturates at a higher level in more concentrated alloys. A concentration as low as 0.02% reduces the initial rate of loop growth by a factor of 4 to 5. Considerable attention has been given to the problems of obtaining accurate measurements of the loop area per unit volume in foils irradiated in the pre‐thinned state, and a number of corrections have been applied. An unusual surface denudation effect is observed. The results are explained in terms of the effect of trapping on the mobility of both the interstitial atoms and the vacancies.
Spin‐forbidden Transitions of Co++ Complexes
Authors: Truţlia AtH.
Published: July 2007

A similarity is shown between the spectra of the tetrahedral and octahedral symmetry bivalent cobalt complexes in the 17000 to 20200 cm−1 region. Various interpretations of this similarity are discussed, special mention being made of the positions of the peaks in the corresponding absorption spectra.
Ferromagnetic Resonance and the Ionic Composition of Cobalt Substituted Nickel Ferrite
Authors: Pointon A. J. , Robertson J. M.
Published: July 2007

A number of ferrites have been prepared with the nominal composition NiCoxFe2−xO4 with x in the range 0 to 0.03. The ferromagnetic resonance linewidths of these ferrites have been investigated as a function of the conditions of preparation and of the cobalt content. An explanation of the variation of the linewidth, as corrected for the porosity broadening, is discussed in terms of the ionic composition of the ferrite. It is found that in order to obtain a complete explanation it appears necessary to postulate a cation disorder process which gives a positive contribution to the magnetic anisotropy constant K1.
Dynamical Theory of the Images of Microtwins as Observed in the Electron Microscope
Authors: Remaut G. , Gevers R. , Lagasse A. , Amelinckx S.
Published: July 2007

In part II the dynamic two‐beam theory of the images of two superposed parallel coherent walls is presented. This situation occurs at overlapping ferroelectric and antiferromagnetic domain walls, enclosing microtwins characterized by very small twin vectors. In this paper the results deduced from the analytical theory developed in part II are compared with computed fringe profiles which are computed exactly. Very good agreement is found, in particular concerning the nature of the extreme fringes, the spacing and the contrast of the fringes, the mean intensities in the overlap and non‐overlap regions and the geometry of the image of a microtwin with increasing thickness. The results of the theory are illustrated by observations of plate‐ and wedge‐shaped microtwins in barium titanate and cobalteous oxide. It is found that the theoretical predictions about the features and general aspect of the images are supported by these observations.
Piezoresistance of Cadmium Antimonide
Authors: Tovstyuk K. D. , Bercha D. M. , Pankevich Z. V. , Rarenko I. M.
Published: July 2007

A theoretical and experimental study is made of the piezoresistance of p‐ and n‐type CdSb. The stress applied along the three crystal axes produces a change in the resistivity of opposite sign. The proposed theory of nonequivalent valley Δ, Λ, and Σ, which follows from the low symmetry of the crystal, explains the observed effects in n‐type CdSb, while a theory involving three nonequivalent shifted valence‐maxima in Γ is in good agreement with the experimental results for p‐type CdSb.
Electron Effective Masses in Heavily Doped n‐Type CdxHg1−x Te
Authors: Mali M.
Published: July 2007

Electron effective masses (m*) for n‐type CdxHg1−x Te with x < 0.2 and a free electron concentration N in the range 1.25 to 1.4 × 1018 cm−3 are obtained from measurements of thermoelectric power as a function of magnetic field. The values of m* can be explained on the basis of the energy band model of Groves and Paul with parameters P = 8 × 10−8 eV cm and |E0| ≤ 0.19 eV.
Effect of Excitons on the Scattering of Neutrons by Crystals
Authors: Glauberman A. E. , Ruvinskii M. A.
Published: July 2007

An investigation is made of the magnetic scattering of slow neutrons by non‐localized Mott excitons, and nuclear scattering by polarizing excitons of the Dykman‐Pekar type. It is shown that the effective cross‐sections for magnetic scattering by one exciton are equal, to within at least an order of magnitude, to the corresponding quantities for magnetic scattering by free electrons. The cross‐sections are also comparable with the cross‐sections for scattering by the electrons of impurity centers. The cross‐section for nuclear scattering by a polarizing exciton is of the same order as in the case of a polaron.
Fuchs's Relations in Alkali Halides and Their Application to the Lattice Dynamics of Lithium Fluoride
Authors: Verma M. P. , Dayal B.
Published: July 2007

A discussion is given of the work of Lowdin and Lundqvist in which the failure of Cauchy relations in ionic crystals is attributed to the existence of a many‐body potential arising from the overlap of atomic wave functions. It is shown that this many‐body interaction may be represented by a volume force which satisfies Fuchs's relations. A simple model is developed incorporating volume forces phenomenologically. In addition to this, the three‐body interaction introduces an effective charge in to the Coulomb term of the point‐ion model. The model is applied to lithium fluoride and good agreement is obtained between the theoretical and observed values of cv.
Observations des défauts primaires dans les cristaux de fluorure de lithium irradiés par les neutrons thermiques à 77 °K
Authors: Comes R. , Lambert M. , Perret R. , Guinier A.
Published: July 2007

On met en évidence la formation directe, dans des cristaux de fluorure de lithium ayant reçu 1.7 × 1018 neutrons thermiques par cm2, de zones de défauts ponctuels associées aux fissions. Ces zones occupent au moins la moitié du volume du cristal; elles ne sont plus visibles au‐dessus de 110 °K.
Some Transport Properties of Semiconductors under Uniaxial Stress
Authors: Grynberg M.
Published: July 2007

The calculations presented in this paper are valid for the III‐V and II‐VI semiconducting compounds with zinc‐blende structure. Under uniaxial stress the spherical energy surfaces become ellipsoidal. The galvanomagnetic coefficients for n‐type material are calculated following the method described by Żukotyński and Kołodziejczak, and assuming a dispersion law E = E (k,\documentclass{article}\pagestyle{empty}\begin{document}$ \hat \varepsilon $\end{document}) for these bands of the type obtained by Pikus. With the assumption of an isotropic relaxation time, formulae are obtained for the transverse magnetoresistance, thermoelectric power in a magnetic field, and Nernst‐Ettingshausen coefficient. By solving Maxwell's equations with a high‐frequency conductivity tensor, expressions are obtained for the Faraday effect, stimulated birefringence due to free carriers, and plasma frequency under uniaxial stress.
The Curie Temperature of LiNbO3
Authors: Smolenskii G. A. , Krainik N. N. , Khuchua N. P. , Zhdanova V. V. , Mylnikova I. E.
Published: July 2007

Single crystals of LiNbO3 are grown by the flux method. Measurements are made in the temperature range 20 to 1170 °C of the dielectric constant ϵ, dielectric loss and relative thermal expansion ΔLl/l along the polar axis (the three‐fold axis x3) and perpendicular to the glide plane (x1). A sharp maximum in ϵ corresponding to a decrease in volume is observed in the x3 direction at 1140 °C. This temperature is assumed to be the Curie temperature of LiNbO3 which corresponds to the transition from an electrically ordered state (ferro or ferrielectric, rather than antiferroelectric) into a paraelectrical state. The temperature dependences of ϵ and Δl/l below the Curie temperature show several similar anomalies. Some of these anomalies may be due to phase transitions.
Etude et essai d'interprétation du stade III de recuit dans le nickel
Authors: Peretto P. , Dautreppe D. , Moser P.
Published: July 2007

Une étude par traînage magnétique du Nickel pur ou dopé irradié aux neutrons et aux électrons à très basse température permet un essai d'interprétation du stade III. Ce stade serait dû à la destruction d'agglomérats d'interstitiels, dont la structure évoluerait au cours du stade II.
Transmission Electron Microscope Study of Natural Radiation Damage in Zircon (ZrSiO4)
Authors: Bursill L. A. , McLaren A. C.
Published: July 2007

Zircons from different localities show considerable variation in physical properties, and it is generally accepted that these variations are the result of α‐radiation damage due to the presence of radioactive impurities, in particular, uranium and thorium. Transmission electron microscopy has been used to study the radiation damage as a function of α‐dose (D) in a number of zircons. No damage was observed in crystals for which D < 1014 α/mg. However, black spot contrast was observed in crystals for which D = 1015 α/mg. Annealing experiments and electron spin resonance studies suggest that the black spots are due to clusters of oxygen interstitials. Crystals for which D > 1016 α/mg were, on X‐ray evidence, glassy (metamict). However, the electron diffraction patterns and micrographs showed that these crystals were composed of slightly misoriented zircon crystallites about 100 Å in size. After annealing, these metamict crystals showed dislocation loops and networks and the single crystal character was restored. The dislocation loops appear to lie on {101} planes and have Burgers vectors parallel to 〈101〉. Inspection of the crystal structure of zircon suggests that this is a likely slip system for zircon. Both interstitial and vacancy dislocation loops were observed. These results suggest a mechanism for the transformation from normal to metamict zircon and this is discussed.
Specific Electrical Conductivities of Tantalum‐Molybdenum Alloy Single Crystals
Authors: van Torne L. I.
Published: July 2007

The specific electrical conductivities of electron beam zone refined tantalum‐molybdenum alloy single crystals were measured at 273, 77, and 4.2°K. It was assumed that the Fermi surface of the alloys is an order of magnitude less than that corresponding to a Fermi sphere and the total scattering cross section behaves like 2π (√2 ΛF)2, where ΛF is the wavelength of electrons at the Fermi surface. Under these assumptions, the calculated electrical conductivities showed good agreement with the observed conductivities at 4.2°K for tantalum rich alloys. The divergence between calculated and observed conductivities in molybdenum rich alloys is attributed to the contribution of holes to the conductivity.
Propriétés diélectriques du sulfate de glycocolle
Authors: Telle F. , Lauginie P.
Published: July 2007

Il est possible d'établir entre le champ électrique E et la polarisation P parallèle à l'axe binaire une relation du type E = a P + b P3 + c P5 + d P7 qui rend compte à la fois des valeurs de la constante diélectrique et de la polarisation spontanée. Les coefficients a, b, c, d varient généralement en fonction de la température et a n'est pas une fonction linéaire de la température au‐dessous du point de transition.
Superconductivity in the Close‐packed Intermediate Phases of the VIr, NbIr, NbRh, TaRh, NbPt, TaPt, and Other Related Systems
Authors: Sadagopan V. , Gatos H. C.
Published: July 2007

The superconducting behavior of various close‐packed low symmetry intermediate phases in the VIr, NbIr, NbRh, TaRh, NbPt, TaPt, HfRh, and HfIr systems was investigated. By considering the σ‐phase as a close‐packed phase, a smooth relationship was found between its superconducting transition temperature (Tc) and those of the other close‐packed phases (of a given system) on the one hand and their composition on the other. In each system the σ‐phase exhibited the highest Tc. The normal behavior of the close‐packed phases of the pseudobinary systems “NbRu3”NbPt3. NbIr3NbPt3, “NbOs3”NbPt3, and ZrPt3NbPt3 down to 1.6°K is considered consistent with the model of Gusman and Brout [1].
Isomerieverschiebung der 23,8 keV‐γ‐Linie von 119Sn in verschiedenen Legierungsphasen
Authors: Pobell F.
Published: July 2007

Es wird über Messungen der Isomerieverschiebung der 23,8 keV‐γ‐Linie von 119Sn in Legierungen von Zinn mit sechs seiner Nachbarn im Periodensystem der Elemente berichtet. Die Messungen wurden über den gesamten Konzentrationsbereich der Legierungen durchgeführt. Innerhalb einer einzelnen Phase ist die Isomerieverschiebung konstant. Der Übergang zu einer neuen Phase ergibt eine starke Änderung der s‐Elektronendichte im 119Sn‐Kern. Die Ergebnisse werden diskutiert und mit Messungen der Knight‐Verschiebung verglichen.
Modifizierte Bloch‐Wellen und ihre Anwendung auf den elektronenmikroskopischen Beugungskontrast von Gitterfehlern
Authors: Wilkens M.
Published: July 2007

Die von Penning und Polder [6] und von Kato [8] eingeführten modifizierten Bloch‐Wellen werden auf die Darstellung des elektronenmikroskopischen Beugungskontrastes angewandt. Man erhält Differentialgleichungen, die die von den Gitterstörungen induzierte Streuung zwischen den modifizierten Bloch‐Wellen beschreiben. Die Störparameter der Gleichungen sind proportional zu den zweiten Ableitungen der Verschiebungskomponenten, d. h. proportional zu den Gitterkrümmungen und umgekehrt proportional zu der dem Beugungsvektor zugeordneten Fourier‐Komponenten des Potentials. Die Gleichungen ergeben eine klare Trennung zwischen Phasenkontrast und Streukontrast, die beide auf physikalisch wesentlich verschiedenen Ursachen beruhen und beide zum elektronenmikroskopischen Beugungskontrast von Gitterfehlern beitragen.
Observation des domaines en rubans dans les lames minces de fer pur par microscopie électronique
Authors: Bourret A. , Dautreppe D.
Published: July 2007

Des observations de domaines magnétiques dans le fer pur aminci sont faites par microscopie électronique (méthode de Lorentz). Les lames ont une orientation préférentielle (111). A l'intérieur des domaines on observe une structure en rubans (stripe domain) pour des épaisseurs supérieures à 1300 Å. Ces rubans sont parallèles à l'aimantation moyenne de chaque domaine. Un modèle simple d'oscillation de l'aimantation est proposé et analysé.
Note on Critical Points and Betti Numbers
Authors: Nusimovici M.
Published: July 2007

The number of van Hove critical points in the Brillouin zone of a crystal is at least equal to one of the Betti numbers defined in topology [1]. In this paper these numbers are shown to be equal to the binomial coefficients.