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 (T_c), irreversibility fields (μ₀H_irr), upper critical fields (μ₀H_c2), 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 T_c 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 μ₀H_irr and μ₀H_c2 values decrease with the increase of the Cr addition. At absolute zero temperature (T = 0 K), the extrapolation of the μ₀H_irr(T) and μ₀H_c2(T) curves is used to obtain the μ₀H_irr(0) and μ₀H_c2(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 μ₀H_irr(0) and μ₀H_c2(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.