Effect of magnetic particle additions on flux pinning in bulk Y-Ba-Cu-O superconductors

Abstract

Abstract In order to increase the critical current density of high temperature superconductors, it is commonly employed to disperse nonsuperconducting particles as flux pinning centers into the superconductive matrix. For Y-Ba-Cu-O bulk superconductors Y2BaCuO5 (Y211) phase particles are known to be effective pinning centers. It has been proposed that magnetic particles are more efficient pinning centers, since they will have a stronger positive interaction with quantized fluxoids. A combined addition of Y211 and magnetic metal fine powders has been reported to be effective in improving flux pinning performances. Therefore, in this study we aimed at improving the pinning forces of Y-Ba-Cu-O bulk superconductors by introducing the Fe-Al-Si-based alloys that are ferromagnetic. We also studied the effect of the addition of γ-hematite, which is non-magnetic, in order to compare the contribution to the flux pinning enhancement. For comparative study, we measured the trapped field in single-domain bulk superconductors and found that a small addition of Fe-Al-Si based ferromagnetic powders and γ-hematite improved field trapping ability.