Pulsed-field magnetization applied to high-Tc superconductors

The pulsed-field magnetization (PFM) technique has been elaborated as the most efficient and effective tool in magnetizing the melt-processed high-T_c bulk superconductor in the temperature range 30–80 K. The dynamic motion of magnetic fluxes penetrating into the YBCO superconductor during the PFM operation has been analyzed and the flux propagation speed has been accurately evaluated. The viscous force is found to play a very crucial role in the PFM process. Detailed analysis of the flux motion in the presence of both viscous and pinning forces enabled us to find a very efficient method for magnetization by the PFM operation. The iteratively magnetizing pulsed field operation with reducing amplitudes abbreviated as ‘IMRA’ has been developed and proved to be very effective in magnetizing high-T_c superconductors at temperatures as low as 30 K. By making full use of these findings, we constructed a prototype quasi-permanent magnet system capable of producing magnetic field of 0.8 T in the outerspace at 7 mm above the surface of the magnetized YBCO superconductor.