Critical current densities and irreversibility fields of high-T sub c superconductors AuBa sub 2Ca sub n-1Cu sub nO sub 2n+3 (n=3, 4) prepared under high pressure

Critical current densities (J sub c) and irreversibility fields (B sub irr) of high-T sub c superconductors AuBa sub 2Ca sub n- 1Cu sub nO sub 2n+3 [Au-12(n-1)n, n=3, 4] prepared under high pressure were determined from the hysteresis in DC magnetization loop. Both the J sub c and B sub irr values of the Au-1234 phase were larger than those of Hg- and Bi-based cupurate superconductors, but smaller than those of the Y- 123 superconductor. This result suggests that the electronic structure of Au- 1234 is less anisotropic compared with the Hg- and Bi-phases. The Au-1223 phase showed very small J sub c values corresponding to its small superconducting volume fraction.