The ac magnetic response of powder-melting-process Sn-doped YBCO superconductors

摘要

The ac susceptibility measurements as a function of temperature, ac field and dc field have been carried out on the samples of Sn-doped powder-melting-process (PMP method) YBa_2Cu_3O_x. (YBCO) with Y_2BaCuO_x (211) inclusions. The transition temperature T_c is 93 K (onset) and transition width is within 1 K. The ac susceptibility only shows one drop in the real component and one peak in imaginary component up to 5 T, which indicate the PMP YBCO samples with fine 211 inclusions are uniform and have no intergranular transitions and second superconducting phase. The weak-link can be neglected, and the superconducting properties are dominated by the bulk material. The irreversibility line determined from the peak in the out-of-phase component of the susceptibility is steeper and shifts to higher temperature conpared to YBCO single crystals. The results suggest that flux-pinning is enhanced by fine 211 inclusions.