Evaluation of the structural, morphological, and magnetic properties of the RE-358, RE-123, RE-Ca0.1 with RE = Gd and Sm superconductors

In this work, we report the production of the cuprate-type RE₃Ba₅Cu₈O_18-δ (RE-358), REBa₂Cu₃O_7-δ (RE-123), and REBa_1.9Ca_0.1Cu₃O_7-δ (RE-Ca0.1), with (RE = Sm and Gd) superconductors. The materials were synthesized using the solid-state reaction method, with sintering temperatures ranging from 850 to 890°C. A comparative analysis of the three systems and the influence of the substituent cation on their structural, morphological, and magnetic properties was carried out through characterization techniques such as XRD, SEM, and VSM. For the RE-358 system, a predominant orthorhombic phase (space group Pmm2 (25)) was identified, whereas the RE-123 and RE-Ca0.1 systems exhibited an orthorhombic structure (space group Pmmm (47)). SEM results revealed homogeneous and relatively smooth surfaces, attributed to the solid-state sintering reactions at high temperatures. Using vibrating sample magnetometry, magnetization curves were obtained as a function of temperature in Zero Field Cooled/Field Cooled (ZFC/FC) mode. From these measurements, the critical temperature ($T_c$) and irreversibility temperature ($T_{irr}$) values were determined. Magnetic studies reveal that the samples exhibit a superconducting transition within the temperature range of 65 - 86 K, depending on the rare earth (RE) element and the system. Thermodynamic fluctuations in magnetic measurements were analyzed using the Bulavskii, Ledvij and Kogan (BKL) model that analyzes fluctuations from the Lawrence-Doniach (LD) model, with this model the parameters of penetration depth ${\lambda }_{ab}$, coherence lengths ${\xi }_{ab}$, and ${\xi }_c$, corresponding to the ab planes and the c direction, respectively, were obtained.