Superconducting Properties of Iodine-Intercalated Bi{sub}2Sr{sub}2Ca{sub}2Cu{sub}3O{sub}(10+x)

摘要

The superconducting properties of iodine-intercalated high-temperature superconducting Bi{sub}2Sr{sub}2Ca{sub}2Cu{sub}3O{sub}(10+x) phase (Bi-2223) were systematically studied. It was found that for samples containing a significant amount of Bi{sub}2Sr{sub}2CaCu{sub}2O{sub}(8+x), iodine intercalation results in the dramatic decrease of the inter-granular critical current density, as well as a significant decrease of the critical temperature (T{sub}c), the critical current density in the grains (J{sub}(cg)), and of the amount of Bi-2223. For samples with a large amount of Bi-2223, T{sub}c changes insignificantly, whereas J{sub}(cg) can even increase. We argue that the different behavior of the superconducting parameters is the result of various oxygen concentrations, and we explain the effect of iodine intercalation based on the parabolic dependence between T{sub}c and the number of holes per CuO{sub}2 layer. The H(T) curves (determined from the peak position in the loss signal of ac susceptibility) for intercalated samples deviate significantly from the quasi 2D-like behavior, pointing toward an enhancement of the 3D fluctuations of vortices. For the change in the values and dimensionality of the flux pinning in the process of the intercalation, we attempted a qualitative explanation based on the models proposed in literature.