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

Abstract

Magnetic hysteresis and flux creep phenomena of grain aligned HgRe 0.18Ba 2Ca 2Cu 3O y powder samples have been measured by SQUID and PPMS. The critical current densities for two field directions of B∥ c-axis and B∥ ab-plane showed J c( B∥ c-axis)> J c( B∥ ab-plane) in low temperature region. But the J c( B∥ c-axis) began to reduce abruptly at a certain temperature and became smaller than the J c( B∥ ab-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( lnΔM/ ΔM 0)/ d ln t| reduces at temperature which is approximately the same as the J c( B∥ c-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.