Comparison of Flux Pinning Mechanism in Laser Ablated YBCO and YBCO:BaZrO_3 Nanocomposite Thin Films

摘要

Thin films of YBCO and YBCO:BaZrO_3 (BZO) nanocomposite have been deposited using the pulsed laser deposition technique. Substantial increase in critical current density (J_C) and pinning force density (F_p) of the nanocomposite thin films was observed. The possible pinning mechanism in YBCO:BZO nanocomposite thin films has been explored and compared with the pinning mechanism in pure YBCO thin film by studying the variation of J_C with magnetic field (B) and temperature. In the intermediate field regime (0.1-1 T), J_C follows B~(-α) with nearly similar values of α for YBCO and YBCO:BZO nanocomposite thin films indicating similar pinning mechanism in both thin films. The variation of J_C with reduced temperature (t = T/T_C) has been studied for both the films and it was observed that the mechanism of pinning in both YBCO and YBCO:BZO thin films is similar (δT_C pinning). The observed enhanced values of J_C and F_p of the nanocomposite thin film is attributed to the presence of BZO nanoparticles, which induces more defects due to lattice mismatch between YBCO and BZO leading to improved flux pinning properties of the nanocomposite thin film.