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1.
T. Grenet J. Delahaye M. Sabra F. Gay 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):183-197
We present a study of non-equilibrium phenomena observed
in the electrical conductance of insulating granular aluminium thin films.
An anomalous field effect and its slow relaxation are studied in some
detail. The phenomenology is very similar to the one already observed in
indium oxide. The origin of the phenomena is discussed. In granular systems,
the present experiments can naturally be interpreted along two different
lines. One relies on a slow polarisation in the dielectric surrounding the
metallic islands. The other one relies on a purely electronic mechanism: the
formation of an electron Coulomb glass in the granular metal. More selective
experiments and/or quantitative predictions about the Coulomb glass
properties are still needed to definitely distinguish between the two
scenarios. 相似文献
2.
The formalism developed in the first two papers of this series is applied to the investigation of a new weak-field model. This crystal-field model lies on the use of a symmetry-adapted weak-field basis and an effective Hamiltonian involving in a symmetrical way both spin- and orbit-dependent contributions. Some general properties of this Hamiltonian are studied and complete calculation of its matrix elements is conducted in a symmetry-adapted weak-field basis in the case of an arbitrary configuration nlN in any symmetry. The case of a configuration ndN in octahedral symmetry is fully explored. In this case, the proposed weak-field model is restricted to a 12-parameter model which accounts for isotropic and anisotropic Coulomb interactions, isotropic and anisotropic spin-orbit interactions, and crystal-field interactions. A comparison between this 12-parameter weak-field model and the 14-parameter strong-field model is established. Equivalence between the latter two models requires two constraint relations to be satisfied for some strong-field parameters. These two relations are examined with various viewpoints. 相似文献
3.
4.
From measurements performed on different polymeric glass-forming liquids using differential scanning calorimetry (DSC), we determined the values of the fragility index m according to the concept proposed by Angell. We calculated the average size of a cooperative rearranging region (CRR) at the glass transition i.e. z(Tg), according to the definition proposed by Solunov. This quantity is linked to the Kauzmann temperature which was determined from dielectric spectroscopy or viscosimetry measurements performed on different samples including three-dimensional polymeric networks and linear polymer families with variable lateral chain lengths. By using our experimental data and others collected in the literature in order to scan a large domain of fragility values, we show that the fragility index m, characterising the glass-forming liquid, can be correlated to z(Tg) which characterises the glass formed. 相似文献
5.
J. Grenet J. M. Saiter C. Vautier J. Bayard 《Journal of Thermal Analysis and Calorimetry》1992,38(4):557-565
The effect of ageing temperature (belowT
g) on physical ageing of glassy PET has been investigated by differential scanning calorimetry. The position of the glass transition endotherm was found to be strongly dependent on the annealing conditions (time, annealing temperature). A single relaxation time model is proposed for the analysis of physical ageing.The variations of the equilibrium relaxation time iso with annealing temperature allow the determination of the parameters of the model. Finally, using these constants, one can determine the thermal past and foresee the thermal future of unknown samples which are of prime importance in processes using temperatures around the glass transition temperature.
Zusammenfassung Mittels DSC wurde der Einfluß der Alterungstemperatur (unterhalbT g) auf das physikalische Altern von glasartigen PET untersucht. Die Lage der Glasumwandlungsendothermen hängt stark von den Temperungsbedingungen (Dauer, Temperungstemperatur) ab. Es wird ein Relaxationszeitmodell für die Analyse physikalischen Alterns vorgeschlagen.Die Parameter dieses Modelles knnen aus der Änderung der Gleichgewichtsrelaxationszeit iso mit der Temperungstemperatur ermittelt werden. Unter Benutzung dieser Konstanten kann die thermische Vergangenheit unbekannter Proben bestimmt und die thermische Zukunft derselben vorhergesagt werden, was für Vorgänge bei Temperaturen um den Glasumwandlungspunkt von primärer Wichtigkeit ist.相似文献
6.
The compounds crystallize in cubic perovskite-type system. The space group is Fm3m and the cell is entirely ordered. 4a positions (Wyckoff's notation) contain iron and uranium, 4b positions, barium and iron, 8c positions, barium and any holmium, which therefore fills coordinance-12 crystallographic sites. For iron-rich compounds (0 < x ? 0.8), interactions between Fe3+ ions from two magnetic sublattices 4a and 4b are antiferromagnetic. The interactions between the third magnetic sublattice, which corresponds to Ho3+ ions filling 8c positions, and the resultant of the first two, are slightly ferromagnetic. Such data have been obtained with all the other compounds for which the formula is Ba3Fe2?xLnxUO9, where Ln is Yb, Tm, Er, Dy, Tb, and Gd. 相似文献
7.
8.
We show experimentally that the in-plane scattering of surface plasmon polaritons (SPP) is influenced by a perpendicular magnetic field. The average SPP flux is deflected into the direction perpendicular to both its initial propagation direction and the magnetic field direction. From a phenomenological point of view, this is an analogy to the Hall effect for electrons and a 2D equivalent of the photonic Hall effect. 相似文献
9.
The symmetry-adapted formalism and the weak-field model described in the first three papers of this series are applied to the case of a configuration nfN in octahedral symmetry. In this case, the latter weakfield model is restricted to a 30-parameter model which accounts for isotropic and anisotropic Coulomb (repulsion) interactions, isotropic and anisotropic spin-orbit interactions, and crystal-field interactions. A comparison between this 30-parameter weak-field model and a 33-parameter strong-field model is established. Equivalence between these two models requires three constraint relations to be satisfied for some strong-field parameters. The three relations are examined on various viewpoints. 相似文献
10.
It is shown that the conductance relaxations observed in electrical field effect measurements on granular Al films are the sum of two contributions. One is sensitive to gate voltage changes and gives the already reported anomalous electrical field effect. The other one is independent of the gate voltage history and starts when the films are cooled down to low temperature. Their relative amplitude is strongly thickness-dependent which demonstrates the existence of a finite screening length in our insulating films and allows its quantitative estimate (about 10 nm at 4 K). This metalliclike screening should be taken into account in the electron glass models of disordered insulators. 相似文献