Superconducting Properties in LTG-Sm_1+xBa_2-x Cu₃O_y + Low-T_c Nanoparticle Films under Low Temperature and High Magnetic Field

Abstract

We have reported high-J_c Sm_1+xBa_2-xCu₃O_y (SmBCO) films prepared by a low-temperature growth (LTG) technique. The LTG-SmBCO films showed a J_c of 0.28 MA/cm² (77 K, B//c, B=5 T). However, the J_c of these films in the magnetic fields above 5 T dropped and were lower than that of NbTi wire (4.2 K). In this study, we introduced nanoparticles with low T_c (low-T_c-nanoparticles) into LTG-SmBCO films to improve the J_c at the high magnetic field. The LTG-SmBCO + 1.4 vol.% nanoparticle film result in a J_c of 0.37 MA/cm² (77 K, B//c, B = 5 T) and 0.10 MA/cm² (77 K, B//c, B = 8 T). Furthermore, the J_c at 65 K in a field of 16 T (B//c) reached 0.05 MA/cm². Elemental mapping clarified that LTG-SmBCO + 1.4 vol.% nanoparticle film had nanosized low-T_c particles with an x of 0.15-0.30 and low-T_c network with an x of 0.05-0.15, which were dispersed in the high-T_c matrix. We speculate that the J_c under high magnetic field conditions depends not only on the distribution and size of low-T_c regions, but also on the Sm/Ba composition within the low-T_c regions.