Extracting the utmost from the high performance of Sm-Ba-Cu-O bulk superconductors by pulse field magnetization

We have studied the magnetization of a melt-processed Sm-Ba-Cu-O bulk superconductor by magnetic pulses at 77 K. The amount of trapped magnetic flux (ΦT) as a function of the pulse amplitude exhibited a peak, which is attributable to the heating of the sample caused by the fast motion of flux lines in the presence of resistive forces. The peak value of ΦT was about half the amount of magnetic flux that was trapped when the sample was field cooled to 77 K, where the field-cooling (FC) value corresponds to the full capability of trapping magnetic flux by the sample. We found that sandwiching the sample with ferromagnetic materials and iteratively applying magnetic pulses while progressively decreasing the amplitude increases the amount of trapped magnetic flux. By combining these two techniques, ΦT increased to about 90% of that of FC magnetization. (author)