Effect of Sm/Ba substitution on the J_c in magnetic field of SmBCO thin films by low temperature growth technique

We have reported superconducting properties of Sm_1+xBa _2-xCu₃O_y (SmBCO; x = 0.08) thin films prepared by the low temperature growth technique (LTG). LTG process is consisted of two steps as follows; a seed layer is deposited at 830°C on MgO(100), and then upper layer is deposited at 740-780°C on the seed layer. In order to investigate the effect of the fluctuations Sm/Ba composition ratio in the SmBCO matrix, we deposited upper layer with the Sm/Ba composition of x = 0 - 0.12. The SmBCO films with x = 0.04 and 0.08 show critical current density (J _c) at 77 K of up to 5 × 10⁶ A/cm² under 0 T and 1 × 10⁵ A/cm₂ under 5 T for B//c at 77 K, respectively. The J_c of x = 0.12 film dropped more sharply compared with the cases of x = 0.04 and 0.08 films. From the microstructure analysis, it was found that the main phase of x = 0.12 film was Sm-rich (Sn _1.1Ba_1.9Cu₃O_y) phase, while that of x = 0.04 and 0.08 films was stoichiometry. We speculated that the low-J _c of x = 0.12 film in the magnetic fields was ascribed to the low physical meters of T_c and irreversibility field of the Sm-rich SmBCO main phase.