Fluctuation induced magneto-conductivity of Y3Ba5Cu8O18±x and YBa2Cu3O7−d

Abstract

A comparative study of the fluctuation magneto-conductivity in [Formula: see text] (noted [Formula: see text]) and [Formula: see text] (noted [Formula: see text]) polycrystalline samples was carried out. Samples were synthesized in oxygen atmosphere using a standard solid state reaction technique. Phases and microstructure have been systematically investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magneto-conductivity was measured in a magnetic field ranging from 0 T to 7 T applied perpendicular to the current path direction. The magneto-conductivity data were analyzed in terms of the temperature derivative of the resistivity and the logarithmic temperature derivative of the conductivity [Formula: see text], where [Formula: see text] is the fluctuation conductivity. Analyses of the magneto-conductivity data reveal that [Formula: see text] possesses a better quality of intrinsic Josephson junction compared to [Formula: see text] one while in the former one the depression in superconducting temperature is more pronounced. The applied magnetic field narrowed substantially the three dimensions (3D) Gaussian regime and for [Formula: see text] sample this regime is vanished for high magnetic field ([Formula: see text][Formula: see text]1 T). Results are discussed in relation with the difference in the structure and microstructure [Formula: see text] and [Formula: see text]. The upper critical and the irreversibility magnetic fields were estimated and were found to be higher in the [Formula: see text] sample.