Flux Pinning of Y-Ba-Cu-O Films Doped With BaZrO3 Nanoparticles by Multilayer and Single Target Methods

The superconducting properties of YBa₂Cu₃O_7-x (YBCO or 123) thin films doped with BaZrO₃ (BZO) nanoparticles by multilayer and single-target methods were studied and compared. Thin films of 123 + BZO were processed by pulsed laser deposition on LaAlO₃ and SrTiO₃ and single crystal substrates. Multilayer (BZO_{0.6nm-1.4 nm}/123 _{15 nm}) structures were grown by alternating deposition from 123 and BZO targets, and BZO additions of 0-2 vol% were deposited using (123_1-xBZO_x) single-targets. The multilayer and single-target methods of BZO addition caused significant differences of superconducting transition temperatures (T_c) measured by AC susceptibility, and critical current densities (J_c) measured by both magnetic and transport methods as a function of temperature (T), applied magnetic field (H) and angle of H field incidence (thetas) . Single-target films had almost linear decrease T_c of and self-field J_c with BZO vol% addition, and compared to multilayer films had lower J_c (77 K, H < 4 T) however had improved high-field properties for J_c (77 K, H > 4T. Multilayer films had almost no decrease of T_c and self-field J_c for high BZO additions up to 10 vol% and very strong peak of J_c (H// ab in - plane) and constant and high J_c (H, 0 < thetas < 80 deg) . Single-target BZO-2 vol% films had slightly enhanced J_c(H//c-axis), consistent with results by other authors.