Effect Melting Time on the Excess Conductivity and Critical Parameters of BSCCO Cooper Oxide System

Abstract

We report here the effect of melting time (tm = 2.5–4.5 min) on the conductivity and dimensionality of BSCCO cooper oxide system. It is found that the mean field and crossover temperatures (Tcmf, T01, and T02) are increased by increasing tm up to 3.5 min, followed by a decrease with further increase of tm up to 4.5 min. The logarithmic plots of excess conductivity (∆σ) and reduced temperature (Є) reveal three regions of different exponents corresponding to two crossover temperatures in the slope of each plot. Interestingly, the crossover occurs from three dimensional (3D) to zero dimensional (0D/SW) in the mean field region and from 0D/SW to two dimensional (2D) in the critical field region, for the samples melted at tm = 2.5, 4, and 4.5 min, while it occurs from (3D) to one dimensional (1D) and from (1D) to (2D) for the sample melted at tm = 3.5 min. On the other hand, we have estimated several physical parameters such as order parameter exponents (λ), interlayer coupling (K), c-axis coherence length (ξc (0)), anisotropy (γ), Ginsburg number (Gi), critical magnetic fields (Hc(0), Hc1(0), and Hc2(0)), and critical current (Jc (0)) for all samples. It is found that λ1, λ3, K, ξc (0), Gi, and γ are increased by increasing tm up to 3.5 min, followed by a decrease with further increase of tm up to 4.5 min as well as Tc, Tcmf, and T0 behaviors. But the vice is versa for the behaviors of λ2, κ, Hc(0), Hc1(0), Hc2(0), Jc(0), and NG. Moreover, it is observed that the behavior of critical fields and critical current against melting time is controlled by the order parameter exponent of the second region rather than the first and third regions. These results are discussed in terms of the correlation between the effects of melting time on the weak links and the flow of actual supercurrent in the considered system.