Thickness effect on the structure and superconductivity of Nd1.2Ba1.8Cu3O7+x epitaxial films

✍ Scribed by M. Salluzzo; G.M. de Luca; D. Marrè; M. Putti; M. Tropeano; U. Scotti di Uccio; R. Vaglio

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 212 KB
• Volume: 460-462
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2007.03.360

✦ Synopsis

We have studied the effect of thickness on the structure and superconductivity of Nd 1.2 Ba 1.8 Cu 3 O 7+x (NdBCO) epitaxial films deposited on SrTiO 3 (1 0 0) substrates. High quality NdBCO films were deposited by high oxygen pressure sputtering. The samples have been carefully characterized by transport measurements and X-ray diffraction using conventional and synchrotron radiation sources. Two structural transformations are observed. The first one is a crossover from the orthorhombic and twinned structure, typical of thick samples, to a pseudotetragonal phase at thickness lower than 60 unit cells. The pseudotetragonal phase exhibits peculiar X-ray diffuse scattering around the Bragg reflections, associated to nanostructured twinned domains. The second one appears at thickness lower than 20 unit cells and is assigned to a pseudotetragonal-tetragonal transition. The transport properties are not modified at the first crossover, while a substantial decrease of T c and of the number of holes is observed at the pseudotetragonal-tetragonal transformation. Our results suggest that the structural rearrangement and the transport properties are explained by the ordering of Cu(1)O chains.