Abstract
The analysis of the microstructure and superconducting behavior of chemical solution deposited epitaxial YBa2Cu3O7−δ films, with thickness going down to 5 nm has been carried out with the purpose to disclose the behavior of the most common intergrowth in these films, the Y2Ba4Cu8O16. The analysis of ultrathin films is a unique opportunity to investigate the superconducting behavior of these nanoscale defects because of the high concentration created as a consequence of the elastic energy associated to the misfit strain. Magnetic susceptibility and X-ray diffraction measurements evidence a strong decrease of the superconducting volume correlated with an increase of the intergrowth volume fraction. We demonstrate that these intergrowths are non-superconducting nanoscale regions where Cooper pair formation is disrupted, in agreement with their key role as artificial pinning centers for vortices in YBa2Cu3O7−δ films and coated conductors.
Highlights
Since the discovery of high temperature superconductors (HTS) there has been an intensive analysis of the complex relationship between lattice structure, defects and superconducting properties.[1]
A er having achieved epitaxial lms and coated conductors (CCs), i.e. HTS lms grown on biaxially buffered metallic substrates not in uenced by grain boundary disorder, the main issue has become to understand which defects behave as effective arti cial pinning centers (APC) of vortices and increase Jc(H,T) at high temperatures and magnetic elds.[3,4]
We present an analysis of the micro/ nanostructure and superconducting properties of Y123 epitaxial lms of different thicknesses grown by Chemical solution deposition (CSD) where a high concentration of Y248 intergrowths is developed when ultrathin lms are formed
Summary
Since the discovery of high temperature superconductors (HTS) there has been an intensive analysis of the complex relationship between lattice structure, defects and superconducting properties.[1]. Chemical solution deposition (CSD) has been demonstrated to be a very attractive technique for large-scale production of Y123 lms and CCs owing to its cost effectiveness advantage.[17,18] CSD is a prototypical example of Y123 epitaxial growth where secondary phases in the form of nanoparticles can be included.[12,15,19,20,21,22,23] They usually remain randomly oriented, generating a high interfacial energy which partially relaxes through the formation of induced defects such as the Y248 intergrowths.[10,24] in CSD nanocomposites it has been shown that vortex pinning is strongly enhanced by the concentration of these Y248 intergrowths.[9,10,25]. Our results allow to infer the non-superconducting character of the Y248 intergrowths observed in Y123 thin lms.[32,33,34,35]
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