Excess conductivity and magneto-conductivity studies in pure and Ag-doped(La1−xYx)2Ba2CaCu5Oz superconductors

Abstract

The temperature variations of electrical resistivity have been measured on pure and 5 wt% Ag-doped(La1−xYx)2Ba2CaCu5Oz superconductors in the absence and presence of 1 T magnetic field. The electrical resistivitydata in the absence of magnetic field were analysed in terms of fluctuation-inducedexcess conductivity in the mean-field regime by using the Aslamazov–Larkin (AL),Lawrence–Doniach (LD) and Maki–Thompson (MT) models. The fluctuations in theamplitude of order parameter are found to be two dimensional in nature. Themagneto-resistivity data were analysed in terms of fluctuation magneto-conductivity byusing the AL and MT models for layered superconductors and by taking into accountboth orbital and Zeeman terms. These materials exhibit a strong pair breakingeffect and the typical phase breaking time at 100 K is found to be of the order of10−16 s. The typical values of coherence lengths along theab-plane andalong the c-direction at 0 K are found to be 28.5 and 0.4 Å.