Temperature dependence of critical current density and flux creep of Hg(Re)-1223 powdered specimens

Magnetic hysteresis and flux creep phenomena of grain aligned HgRe0.18Ba2Ca2Cu3Oy, powder samples have been measured by SQUID and PPMS. The critical current densities for two field directions of Bparallel toc-axis and Bparallel toab-plane showed J(c)(Bparallel toc-axis)> J(c)(Bparallel toab-plane) in low temperature region. But the J(c)(Bparallel toc-axis) began to reduce abruptly at a certain temperature and became smaller than the Jc(Bparallel toab-plane) in higher temperature region. Such abrupt change was also measured in the flux creep phenomena, i.e. so called flux creep rate S = \d(ln DeltaM/DeltaM(0))/d lnt\ reduces at temperature which is approximately the same as the J(c)(Bparallel toc-axis) anomaly arises. Such anomaly is also observed in the temperature dependence of the magnetization itself at relevant magnetic field. Temperature dependence of the S is successfully analyzed by the Kim-Anderson model and the collective creep model. (C) 2004 Elsevier B.V. All rights reserved.