Pulsed field magnetization of melt-processed Y-Ba-Cu-O superconducting bulk magnet

Magnetic fluxes can be trapped in a melt-processed Y-Ba-Cu-O (YBCO) bulk superconductor at 77 K by applying a pulsed magnetic field with a rise time of 0.8 or 2.4 ms. We found that trapped fluxes increase with increasing intensity of applied field up to 1.9 T, but decrease beyond this value; resulting in a peak in the applied field dependence of trapped fluxes. It is also found that creep of trapped fluxes can be largely suppressed when pulsed fields exceeding 1.9 T are applied. Other new phenomena characteristic of pulsed field magnetization were also found and discussed. All these results can be explained by taking into account the significant contribution of the viscous force and the resulting heat generation due to the viscous motion of fluxes.