High trapped fields in melt-textured YBa/sub 2/Cu/sub 3/O/sub 7-δ/

Abstract

Bulk melt textured YBCO material with single-domain grains up to 35 mm in diameter was prepared by a modified melt-texture process. The maximum trapped field B/sub o/ measured in the 1 mm gap between two single-grain disks was found to increase from 1.2 T at 75 K up to 9.6 T at 46 K, which is the highest trapped field achieved in nonirradiated samples. A strong exponential decrease of the trapped field with increasing temperature found in most of the cases can be explained by flux creep within the framework of collective pinning assuming weak pinning. A weaker B/sub o/(T) dependence and higher B/sub o/ values at temperatures between 55 and 75 K were observed in newly processed YBCO material. A pronounced peak effect found in the field dependence of the critical current density suggests strong pinning in this material. For applications of YBCO samples in superconducting magnetic bearings, an effective method for magnetizing the superconductor is required. Results of magnetizing YBCO samples by applying pulsed magnetic fields are presented.