Flux pinning in Ba1−xKxFe2As2 superconductor with splayed columnar defects

It has been theoretically proposed that the enhancement of the critical current density (Jc) through dispersing the angle of columnar defects should be greater than that of parallel columnar defects. Yet, the complication caused by decrease in pinning owing to vortex-field misalignment upon tilting of columnar defect makes it a crucial task to determine the optimal splay angle in order to fully take advantage of enhanced pinning among splayed systems. Using Ba0.6K0.4Fe2As2 as a target material, we probe the effects of various splay angles on Jc and determine that the 'optimal-angle' lies within the small angle range (0--10∘).