Search results for "Resistivity"
showing 10 items of 385 documents
Vortex–antivortex unbinding in oxygen-deficient YBa2Cu3O7− films
2007
Abstract In-plane zero-magnetic-field current–voltage ( I – V ) characteristics of oxygen-deficient YBa 2 Cu 3 O 7− δ films (7 − δ ∼6.5, 6.55, and 6.65) were thoroughly investigated. A good agreement with the quasi two-dimensional (2D) vortex–antivortex unbinding scenario was observed, similar to the behaviour of highly anisotropic Bi 2 Sr 2 CaCu 2 O 8+ δ films. The temperature variation of the I – V exponent allows the determination of the Berezinskii–Kosterlitz–Thouless transition temperature T KT at the superconducting Cu–O layer level, and the mean-field critical temperature T c0 . We found that both T KT and T c0 increase with increasing doping, and T c0 remains in the region of the …
Length-scale-dependent vortex-antivortex unbinding in epitaxialBi2Sr2CaCu2O8+δfilms
1998
The supercurrent transport properties of epitaxial ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ films in zero applied magnetic field were investigated in a temperature interval of \ensuremath{\approx}20 K below the mean-field critical temperature ${T}_{c0}.$ The modification of the shape of the $I\ensuremath{-}V$ curves observed by varying the temperature was explained in terms of vortex-fluctuation-induced layer decoupling and vortex-antivortex unbinding, revealing a strong probing-length dependence. The change of the effective dimensionality of thermally excited vortices involved in the dissipation process leads to the appearance of …
Magnetoresistance in the HF Metal at Zero Temperature
2014
In this chapter we consider the paradoxical behavior of the residual resistivity \(\rho _0\) of HF metals in magnetic fields and under pressure. Our consideration is based on the idea of flattening of the single-particle spectrum \(\varepsilon (\mathbf{p})\) that profoundly effects on the specific heat \(C\), thermal expansion coefficient \(\alpha \) and magnetic susceptibility \(\chi \) in the normal state, the jump of \(C\) at the point of superconducting phase transition etc. We show that FC associated with flat bands contributes to the residual resistivity \(\rho _0\), while the application of the magnetic field or pressure to the system with a flat band removes the flat band and leads …
Growth characteristics of sputter-deposited thin films
1996
Thin films of the heavy-fermion superconductor were deposited on various substrate materials in various orientations by means of a quasi-multilayer sputter process. Strongly (0001)-textured growth of the hexagonal compound was found for a uranium content in the range of 23% to 28% on sapphire and with perfect in-plane order on the latter substrate material. Atomic force microscopy and scanning electron microscopy revealed a Vollmer - Weber-like growth mode resulting in the development of large compressive strain in films on . As a result the electronic transport properties - in particular the temperature dependence of the resistivity - were strongly renormalized. Strong deviations from the …
Structure and electrical resistivity of mixed-valent EuNi2P2 at high pressure.
2014
The structural properties and electrical resistivity of homogeneous mixed-valent EuNi2P2 are studied at pressures up to 45 GPa. No structural phase transition is observed in the whole pressure range and the overall pressure behavior of the structural parameters is similar to that of related compounds in the collapsed tetragonal ThCr2Si2-type structure. Electrical resistivity measured up to 31 GPa at temperatures between 4 and 300 K exhibits continuous changes from the behavior typical for a mixed-valent Eu system to that of a normal metallic system at pressures above 20 GPa, indicating a transition of the strongly mixed-valent Eu atoms with a valence ~2.5 towards a pure trivalent state. No …
Polymer solution processing of (Bi, Pb)SrCaCuO
1991
Abstract A simple polymer processing route to the 110 K phase (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10+δ superconductor has been developed. The influence of the polymer to metal starting ratio, as well as the sintering temperature and time on the quality of the resulting superconducting powders has been studied by XRD, a.c. susceptibility and resistivity measurements. Microstructure of ceramic compacts has been studied by SEM, and qualitatively analysed by EDS for compositional homogeneity. The results indicate that the polymer synthesis route described here may offer a good alternative to the conventional solid state preparation methods towards attaining homogeneous 110 K superconductor powder withi…
Electrophysical, Magnetoresistivity and Magneto-optical Properties of Multilayer Materials Based on Nanocrystalline and Amorphous Films
2012
In work is presented to the results of complex investigate of phase formation, thermal resistivite, magnetoresistive and magneto-optical properties of multilayers based Fe and Pd, Ag or Ge, which obtained by sequential condensation of the layers with following thermal annealing. Investigation of phase formation processes of thin film systems and established of correlation between this processes and above-mention physical properties. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35009
Size Distribution, Mechanical and Electrical Properties of CuO Nanowires Grown by Modified Thermal Oxidation Methods
2020
Size distribution, Young&rsquo
Growth of metal/oxide periodic multilayer : relation between structure and electrical behaviour in systems based on titanium and tungsten
2014
Periodic multilayers have found many applications in the fields of optics, mechanics or electronics. However, few studies focus on the electrical responses of the metal/oxide periodic structures versus temperature. The interest of this work was focused on the characterization of the multilayers and their electrical properties versus temperature. In TiO/Ti/TiO/TiO2 and WO/W/WO/WO3 systems produced by the reactive gas pulsing process, sample structures were established by transmission electron microscopy for sublayers thicknesses between 1.3 and 50.8 nm. Then, this study highlights a modification of conventional electrical behavior versus temperature. An empirical relationship was established…
Mechanical, thermal and electrical properties of nanostructured CNTs/SiC composites
2018
International audience; Dense SiC-based nanostructured composites reinforced by well-distributed carbon nanotubes (CNTs) were elaborated for the first time by spark plasma sintering (SPS) without sintering additive. Microstructures of materials containing different amounts of CNTs – up to 8.0 vol% – were correlated with their mechanical, electrical and thermal properties. A continuous decrease of the SiC grain size was observed when the amount of CNT was increased, while the evolution of density showed a different behavior that could be explained by the particular combination of SPS technique with the electrical resistivity evolution of the green bodies. Optimal effect of CNTs addition on h…