Superconducting properties of ErBCO films with BaMO₃ nanorods (M = Zr and Sn) by pulsed laser deposition

Ba complex oxides such as BaMO₃ (BMO, M = Zr and Sn) were incorporated into ErBa₂Cu₃O_7-δ (ErBCO) films on SrTiO₃ (STO) substrates for realizing higher critical current densities (J_c) in magnetic fields. Nanorods of BMO were formed in the ErBCO films with the rod diameter of about 10-20 nm. Crystal grain alignment of both ErBCO films with BZO and BSO were found to be worse with increasing the doping concentration of BMO into the films, resulting in critical temperature (T_c) degradation for the ErBCO films. J_c of the ErBCO films were enhanced by the corporation of these BMO nanorods in the magnetic fields (B) applied particularly parallel to the c-axis (B//c). Additionally, it was observed that the J_c values of the ErBCO films with BSO were higher than those of ErBCO films with BZO in the all measured magnetic fields (B//c), which indicated that the BSO nanorods acted as more effective pinning centers in ErBCO films. Extremely high J_c of 0.41 MA/cm² was performed for the ErBCO film with BSO of 4.9 mol% in the magnetic field (B//c) of 3 T. We concluded that not only the decision of pinning materials, but also optimization of the three factors of crystallinity of the superconducting film, T_c of the superconducting film, and doping concentration of the pinning materials into the superconducting film were important to realize higher J_c in a magnetic field.