Magnetoresistivity study on Cr added Bi-2212 superconductor ceramics with experimental and theoretical approaches

This study investigates the change of the superconducting and physical properties of Cr added Bi-2212 superconductor ceramics prepared by the conventional solid-state reaction method with the aid of magnetoresistivity measurements performed in a range from 0 to 7 T. The zero resistivity transition temperatures (Tc), irreversibility fields (μ0Hirr), upper critical fields (μ0Hc2), penetration depths (λ) and coherence lengths (ξ) are estimated from the magnetoresistivity curves. Furthermore, activation energy (U0) values of the ceramics produced are found using thermally activated flux creep model. The results show that the Tc value decreases from 80.7 K (52.6 K) to 70.4 K (13.4 K) for the pure sample (the sample doped with 1wt% Cr) with the increasement in the applied magnetic field. Likewise, the U0 values reduce dramatically with increasing applied magnetic field. In fact, the U0 of 302 K is the smallest at 7 T applied field for the sample doped with 1wt% Cr. Additionally, the μ0Hirr and μ0Hc2 values decrease with the increase of the Cr addition. At absolute zero temperature (T = 0 K), the extrapolation of the μ0Hirr(T) and μ0Hc2(T) curves is used to obtain the μ0Hirr(0) and μ0Hc2(0) values of the samples. The inner (latter) is found to be about 85.87 T (191.21 T) T and 13.88 T (86.89 T) for the pure sample and the sample doped with 1wt% Cr, respectively. On the other hand, the ξ and λ values inferred from μ0Hirr(0) and μ0Hc2(0) are obtained to increase from 13.13 to 19.48 Ǻ and 19.60 to 48.73 Ǻ, respectively as the Cr addition level increases in the Bi-2212 bulk superconductor, presenting that the Cr doping suppresses the physical and superconducting properties of the samples as a result of the pair-breaking mechanism.