Numerical analysis of magnetic levitation forces for bulk superconductors with different superconducting junctions between multiple-seed-growth domains

Abstract

We studied magnetic levitation forces for bulk superconductors through numerical analysis. We virtually varied the superconducting junctions between domains formed through multiple seeding (four seeds) and investigated the effect of the following parameters on the magnetic levitation force: (1) the critical current density J c across grain boundaries (GBs) or superconducting junctions between crystal domains. J c across GBs was varied from 0% to 100% of the base material’s J c and (2) the depth of the insulation phase (0% of the base material’s J c ) formed between domains. For parameters in (a), we found that in the presence of superconducting junctions between crystal domains with less than 50% for the ratio of J c to the base materials’ J c , the magnetic levitation force decreased significantly under the conditions where the superconducting bulk and the permanent magnet face each other like this study. Furthermore, for 100% of the base J c , the largest levitation force was generated by the first layer (0–1 mm thick), while with a reduced superconducting junction (25% of J c to 0% of J c ), the deeper layers also contributed to the levitation force. For the parameters in (2), even a thin insulation phase layer between crystal domains significantly affected the magnetic levitation force, and different bulk layers (each 1 mm thick) below the insulation phase showed different levels of contribution to the levitation force.