J_c enhancement in YEa₂Cu₃O_x thin films by introduction of one-dimensional artificial pinning centers

A novel technology to introduce artificial pinning centers (APCs) into YBa₂Cu₃O_7-δ (YBCO) thin films prepared by pulsed laser deposition (PLD) was investigated for a drastic improvement of J_c in the films. Linear-like defects (one-dimensional APCs) were introduced perpendicular to the surface of the c-axis oriented films during the deposition process by using distributed Y₂O₃ nano-islands on substrates. The density of nano-islands was varied within 0.8 - 1.2 × 10¹⁰/cm² by PLD. A normalized resistivity as a function of temperature in magnetic fields shows a sharper resistivity drop for the film with APC, compared to pure YBCO film. J_c of the film with APC was also increased to 0.12 MA/cm² (77 K, B//c, 5 T), which was about two times higher than that of the pure YBCO film. The film had a very large J _c peak when the field was applied close to the c-axis. The peak J_c increased with the number density of Y₂O₃ nano-islands. This indicates that strong APCs parallel to the c-axis were incorporated into the YBCO film.