Effect of Sm/Ba Substitution on the<tex>$J_c$</tex>in Magnetic Field of SmBCO Thin Films by Low Temperature Growth Technique

Abstract

We have reported superconducting properties of Sm/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 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/spl deg/C on MgO(100), and then upper layer is deposited at 740-780/spl deg/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/sub c/) at 77 K of up to 5/spl times/10/sup 6/ A/cm/sup 2/ under 0 T and 1/spl times/10/sup 5/ A/cm/sup 2/ under 5 T for B//c at 77 K, respectively. The J/sub 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/sub 1.1/Ba/sub 1.9/Cu/sub 3/O/sub y/) phase, while that of x=0.04 and 0.08 films was stoichiometry. We speculated that the low-J/sub c/ of x=0.12 film in the magnetic fields was ascribed to the low physical meters of T/sub c/ and irreversibility field of the Sm-rich SmBCO main phase.