Sm/Ba Composition Ratio on the Filed Dependence of J_c in Sm_1+xBa_2-xCu₃O_y Thin Films

Abstract

We have reported the superconducting properties of Sm_1+xBa_2-xCu₃O_y (SmBCO; x=0.08) thin films prepared by the low-temperature growth (LTG) technique. To investigate the effect of the Sm/Ba composition ratio (x) in the SmBCO, we deposited an upper layer with the Sm/Ba composition of x=0.00-0.12. From the result of the etch pit and composition analysis, we found that the Sm/Ba composition ratio in the SmBCO film influenced possible pinning centers, such as linear defects including screw dislocation and edge dislocation, and nano-size low-critical temperature (T_c) phase acting as a field-induced pinning center. Moreover, we noticed the Sm/Ba composition ratio in the SmBCO film influenced T_c and critical current density (J_c). As a result, the SmBCO films with x=0.04 and 0.08 showed J_c=2.8 × 10⁵ A/cm ² and 1.7 × 10⁵ A/cm² (77 K, B//c, 8 T), respectively.