High pressure synthesis and superconducting properties for the multi-layered Ba2Can−1CunO2n(O,F)2 (n = 4 and 5)

Abstract

We prepared multi-layered oxyfluoride superconductors, Ba2Can−1CunO2n(O,F)2 (n=4 and 5) using high-pressure apparatus. These phase are the n=4 and 5 members of a homologous series, M2Can−1CunO2n(O,F)2 [0M2(n−1)n-F] reported previously. X-ray studies indicated that they have tetragonal structures with a=3.863Å, c=33.75Å for n=4 and a=3.862Å, c=40.18Å for n=5. Superconducting transition temperature were 86.6K for n=4 and 75.7K for n=5, respectively. The critical current density (Jc) and irreversibility field (Hirr) were determined from M–H curves using the Bean’s model. Jc and Hirr of 0Ba2(n−1)n-F (n=4 and 5) decreased rapidly with increasing temperature. Jc (5K, 1T) shows 1.70×106A/cm2 for n=4 and 1.93×105 A/cm2 for n=5. The estimated values of Hirr (5K) are about 70T for n=4 and 17 T for n=5.