Comparative study of magnetic fields trapped in YBa₂Cu₃O_y, and SmBa₂Cu₃O_y superconducting bulks

We have measured the trapped field distribution in plates of melt processed YBa₂Cu₃O_y, (Y123) and SmBa₂Cu₃O_y, (Sm123) superconductors that have different field dependence of the critical current density (J_c). Sm123 materials were fabricated by the oxygen-controlled melt-growth (OCMG) process and exhibited the peak effect. The trapped fields were measured by scanning a Hall probe on the sample surface. Measurements were performed after a field of 3.5 T was applied in the field-cooled process. On the basis of the critical state model, the magnetic field distribution was calculated taking account of the field dependence of the critical current density. The calculated values were in good agreement with the measured data. We have also estimated trapped magnetic fields for Y123 and Sm123 when the grain size is enlarged, which showed that OCMG-processed Sm123 bulk superconductors have greater potential as trapped field magnets.