Effect of Sm/Ba substitution on the Jc 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 (Sm_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.