Comparison of Transport Properties between Tl-(1223) and Tl-(2223) Phases of Tl-Ba-Ca-Cu-O Systems

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Abstract
Thin films of the (1223) phase (Tl-(1223), single Tl-O layer) and the (2223) phase (Tl-(2223), double Tl-O layers) of the Tl-Ba-Ca-Cu-O system were prepared using the laser ablation method. Both films had a high transport critical current density (J c) of 1.5×105 A/cm2 at 77 K in zero magnetic field. When the magnetic field was applied parallel to the a-b plane (a-b plane//B), transport properties in both films at different temperatures were similar. On the other hand, in fields perpendicular to the a-b plane (a-b plane ⊥B), J c of the Tl-(1223) thin film was higher than that of the Tl-(2223) thin film at 40, 60 and 77 K. The irreversible magnetic fields (B c2 * values) obtained from the resistivity change in the magnetic fields were 8.0 and 2.0 T at T/T c=0.6 for the Tl-(1223) and Tl-(2223) thin films, respectively. These results suggested that the thickness of the Tl-O layer, which is non superconductive, determines transport properties for fields applied perpendicular to the a-b plane.