Enhancement of flux pinning in YBa₂Cu₃O_7−δthin films embedded with epitaxially grown Y₂O₃nanostructures using a multi-layering process

Abstract

Nanodot arrays of Y2O3 were dispersed in thin films of YBa2Cu3O7−δ (YBCO) by growing alternating layers of these two species using a pulsed laser deposition method. As a result, critical current density Jc both in applied magnetic field and self-field is enhanced by as much as an order of magnitude, along with a significant increase in the irreversibility field Hirr. High-resolution scanning transmission electron microscopy (STEM) and Z -contrast STEM show that the nanoparticles are crystalline and coherent with the YBCO matrix. Whereas in most other studies pinning has been attributed to the strain fields around the nanoparticles, in this case pinning may actually be due to the nanoparticles themselves ,s incethe delineation between the two species is very sharp and STEM reveals no discernible strain fields in the superconducting material around the nanoparticles. (Some figures in this article are in colour only in the electronic version)