SUPERCONDUCTING PERMANENT-MAGNETS FROM BULK YBA2CU3O7-DELTA SAMPLES

The properties of bulk melt-textured YBa2Cu3O7-delta disks have been i nvestigated with respect for use as trapped field magnets. Large singl e-domain disks up to 35 mm in diameter and 12 mm in thickness were obt ained by a melt-texturing process. The trapped field in the I mm gap b etween two single-domain disks was found to increase from 1.2 T at 77 K up to 9.0 T at 47 K which is the highest trapped field achieved in n onirradiated samples. The trapped field at lower temperatures is limit ed by the mechanical strength of the material for which a value of 25 MPa was estimated. We observed an exponential decrease of the trapped field with increasing temperature, which can be explained by flux cree p in the framework of collective pinning. The activation energy for th is process was determined by relaxation measurements.