Epitaxial growth and superconducting anisotropy of PbSr$_{2}$Y$_{1-x}$Ca$_{x}$Cu$_{2}$O$_{7+δ}$ thin films

Abstract

Thin films of single-crystal Pb1−yBiySr2Y1−xCaxCu2O 7+δ (PbBi1212) were grown on SrTiO3 (100) substrates by a two-step growth technique in which an amorphous film is annealed at 970 • C in a closed ceramic container prepared using the same material as the film. We find that PbBi1212 exhibits superconductivity when the Ca concentration x exceeds 0.3. The effective number of holes per Cu atom n eff is well described as n eff = 0.34x. The highest onset temperature for the superconducting transition attained in the present study is 65 K. The resistivity measurement in a magnetic field reveals that the coherence lengths of Pb1212 (y = 0) are approximately 25 and 2.7 Å along the ab plane and the c axis, respectively.