Enhanced pinning and peak effect in overdoped (Hg, Pb) (Sr, Ba)(2)Ca2Cu3O8+delta superconductors

"Peak effect'' was observed in the magnetization hysteresis loops of both ( Hg, Pb)(Sr, Ba)(2)Ca2Cu3O8+delta polycrystalline bulks and single crystals, and the influence of postannealing on the peak position (H-s. p.) was stud ied, where "s.p.'' means second peak. It was shown that the H-s.p.-T charac teristic curves for a Sr-rich (Hg, Pb)-1223 were located in higher fields t han those reported for conventional Hg-1223 and Tl-1223 single crystals, co rresponding to reduced lattice parameters and electronic anisotropy of the studied compounds. The J(c) (77 K) values of 3 x 10(5), 2.8 x 10(4), and 1. 8 x 10(4) A/cm(2) were estimated for the present single-crystal sample at H = 0, 1, and 2 T, respectively. This confirms the excellent flux-pinning pr operty of (Hg, Pb)(Sr, Ba)(2)Ca2Cu3O8+delta, making them potential candidat es for high current applications. (C) 1998 American Institute of Physics. [ S0003-6951(98)00250-2].