Spatial and Temporal Flux-Trapping Properties of Bulk High Temperature Superconductors Under Static Magnetization Fields

Magnetized YBaCuO bulks are available to enhance the levitation performance of present superconducting maglev systems due to their high trapped fields. To realize a good YBaCuO bulk magnet, we studied the flux-trapping properties of an YBaCuO bulk sample under different magnetization fields from two aspects. Firstly in spatial view, five Hall sensors were employed to measure the trapped magnetic fields at five typical positions of growth sector regions and growth sector boundaries on the seeded surface of the bulk. And then in temporal view, the trapped magnetic fields of these five positions were continually recorded by a real-time data acquisition device during the magnetization process and the succeeding relaxation processes. Results show that the saturated trapped fields at five surface positions of the YBaCuO bulk magnet exhibit the strong spatial inhomogeneity. The trapped fields at the growth sector boundaries are always higher than those at the growth sector regions, due to different critical current density distributions of the bulk superconductor. And the magnetization field required to saturate the center of the bulk is much higher than that of the edge region. But the much high magnetization field will reduce the final trapped field at the edge of the bulk. Moreover the trapped field variation with time is sensitive to the participation of some external ferromagnetism materials. It is found that the adding of an iron plate above the YBaCuO bulk surface is efficacious to restrain the trapped field relaxation.