Enhancement of flux pinning in YBa2Cu3O7-δ thin films embedded with epitaxially grown Y2O3 nanostructures using a multi-layering process

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, since the delineation between the two species is very sharp and STEM reveals no discernible strain fields in the superconducting material around the nanoparticles