Effect of double pinning mechanism in BSO-added GdBa 2 Cu 3 O 7-x thin films

We investigated the effect of self-assembled BSO nano-defects as pinning centers in BSO-added GdBCO films when the thicknesses of films were varied. 3.5 vol. % BSO-added GdBCO films with varying thicknesses from 200 nm to 1000 nm were deposited on SrTiO 3 (STO) substrate by using pulsed laser deposition (PLD) process. For the films with thicknesses of 400 nm and 600 nm, ‘anomaly shoulders’ in J c - H characteristic curves were observed near the matching field. The anomaly shoulders appeared in the field dependence of J c may be attributed to the existence of double pinning mechanisms in thin films. The fit to the pinning force density as a function of reduced field h (H/H irr ) using the Dew-Hughes’ scaling law shows that both the 400 nm- and the 600 nm-thick films have double pinning mechanisms while the other films have a single pinning mechanism. These results indicate that the self-assembled property of BSO result in different role as pinning centers with different thickness.