Magnetization and Demagnetization Studies of an HTS Bulk in an Iron Core

High-temperature superconductors (HTSs) are promising materials in a variety of practical applications due to their ability to act as powerful permanent magnets. Thus, in this paper, we have studied the influence of some pulsed and pulsating magnetic fields applied to a magnetized HTS bulk sample. The bulk sample, the iron core, the two inductors, and the current sources used to magnetize and demagnetize the superconducting bulk in the iron core are presented. Then, we detail various magnetizing and demagnetizing processes and their purposes. For the magnetization studies, we have shown that there is no significant difference between the successive process and the direct process of magnetization. The maximum trapped magnetic field (TMF) is about 1 T, 10 min after the magnetization process. For the demagnetization studies, we propose many results as a hysteresis loop corresponding to the pulsed demagnetizing field influence. Various time evolutions of the TMF are also shown, i.e., when the demagnetizing ac field is applied a few minutes after or several days after the magnetization. This leads to completely different results, from 5%/min to 1%/(6 h) of reduction of the TMF. The results presented here give many practical information to users of superconducting bulk magnets. We assume that decreasing the temperature will increase the capabilities of trapping the magnetic field. We conclude that a strong interest must be kept on the applications of HTS bulks in electrical engineering, preferably at lower temperature than 77 K.