GRAIN-BOUNDARY LINKS AND CRITICAL-CURRENT OF BI2SR2CA2CU3OX AG TAPES/

The nature of grain-boundary links in high-quality Bi2Sr2Ca2Cu3Ox tape s is clarified. The investigations focus on the role that various type s of links play in the restriction of the critical current. The multip le exponential function is found to be a good approximation for the ma gnetic-field dependence of critical current I-c(H). The behaviour of I -c(H) at different temperatures gives clear evidence of the two-dimens ional character of critical current. It is shown that at all temperatu res higher than the Kosterlitz-Thouless transition temperature of isol ated superconducting layers the critical current is totally defined by the Josephson interaction between the layers.