SUPERCONDUCTING PROPERTIES OF (1223) AND (2223) PHASES IN TL-BA-CA-CU-O THIN-FILMS

Thin films of pure single Tl1Ba2Ca2Cu3Ox (1223) phase and Tl2Ba2Ca2Cu3 Ox(2223) phase have been prepared by laser ablation and post-annealing . In particular, when both films were annealed at a low temperature an d for a long time, they had a highly c-axis-oriented structure and a h igh transport J(c) of > 1 x 10(5) A cm(-2) at 77 K in zero magnetic fi eld. Magnetic and transport measurements were performed for both films at different temperatures. When the magnetic field was applied perpen dicular to the a-b plane (a-b plane perpendicular to B), the intragrai n J(c) from the magnetization measurements for the Tl-(1223) thin film was clearly larger than for the Tl-(2223) thin film. Moreover, in the a-b plane perpendicular to B, the transport J(c) of the Tl-(1223) thi n film was higher than that of the Tl-(2223) thin film at high tempera ture (> 40 K). The magnetic field dependence of the global pinning for ce density (F-p = J(c) x B) of both films could be successfully explai ned by Kramer's scaling law, F-p/F-p(max) = 3.5(B/B-c2)(1/2)(1 - B/B- c2)(2), where B-c2* was the irreversibility magnetic field. These dat a indicated that the in-field behaviour of the Tl-(1223) system was su perior to that of the Tl-(2223) system.