Anomalous magnetization behavior in field-cooling magnetization versus temperature curves in Tl-1223/Ag sheathed superconducting tape

Abstract

The zero-field-cooling and the field-cooling temperature dependence of magnetization for Tl-1223/Ag superconducting tape were measured by using SQUID magnetometer at fields varying from 5 Oe to 5 T in the temperature range of 5–150 K. In the field-cooling curves, some anomalous behaviors, i.e., the positive Meissner effect in the curve of 5 Oe and the diamagnetic dip effect at fields up to 5 kOe, were observed. The diamagnetic dip minimum temperature shifts to the lower temperature as increasing the external field, and the relative amplitude decreases with increasing applied field. Moreover, the dip broadens with increasing applied field. The anomalous behaviors may be attributed to the flux pinning and the flux depinning of Josephson-junction networks in the sample. The dip effect at lower fields may be ascribed to the intergrain Josephson coupling networks, and that at higher fields may be due to the intrinsic intragrain Josephson coupling networks.