Repeated pulsed-field magnetization with temperature control in a high-Tc bulk superconductor

We investigated the applicability of high-Tc superconducting bulk magnets to the superconducting Maglev system. A bulk superconductor needs to generate as high a magnetic field as possible to obtain a powerful bulk magnet. The bulk magnet requires a larger external coil and larger power supply, and has a problem that large electromagnetic force is applied to the bulk in the process of magnetization. Therefore, a relatively small magnetic field is preferable to magnetize a high-Tc bulk superconductor. In this study, we magnetized a melt-processed YBCO bulk superconductor by repeated pulsed-magnetic field while controlling its temperature. In this method, a comparatively small pulsed-magnetic field was repeatedly applied to the bulk while lowering the temperature of the bulk from the critical level at intervals of magnetization. For example, the TBCO bulk was magnetized by a series of seven pulsed-magnetic fields, while temperature was lowered from 94 K to 82 K at intervals of 2 K. As a result, it is found that the bulk superconductor can generate a higher magnetic field by using a comparatively small magnetic field