This work reports a detailed structural study by synchrotron x-ray diffraction of several sets of thick YBa${}_2$Cu${}_3$O${}_7$ layers. The samples represent recent advances in flux-pinning design, containing various concentrations of artificial pinning centers: (i) BaZrO${}_3$ nanorods, (ii) BaZrO${}_3$ nanoparticles, and (iii) Y${}_2$O${}_3$ nanoparticles. A statistical analysis was performed in order to separate the effects of defect-induced and intrinsic pinning. We report a statistically significant correlation between the orthorhombic distortion of the YBCO matrix and the pinning strength. Our result implies that the in-plane ordering of oxygen ions in the chain positions accounts for approximately 60$\%$ of the pinning force. The strain-induced pinning mechanism analysis, based on the Eshelby model of elastically strained composites, predicts that small YBCO grain size is a critical component of a strong pinning architecture that can enable critical current density values approaching the depairing limit.

• Received 19 June 2012

DOI:https://doi.org/10.1103/PhysRevB.86.094511