Systematic Studies to Enhance Flux Pinning of (BaZrO₃/YBa₂Cu₃O_7-x)_N Multilayer Thin Films for the Full Landscape of T = 30 K to 77 K

The (M/YBa<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>Cu<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x</sub>)<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> multilayer thin film structure has been studied by many groups, and achieves different microstructures and artificial pinning centers that result in large variations of critical current density (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c)</i> for a large landscape space of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> = 30–77 K, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H_appl</i> = 0–9 T and 0° ≤ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H_appl(θ</i>) ≤ 90°. Herein provides a wide-ranging optimization study of (BaZrO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3,y</sub>/YBa<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>Cu<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x,z</sub>)<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> multilayer films prepared by pulsed laser deposition with y,z layer thickness. Process parameters studied include YBa<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>Cu<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x</sub> (YBCO) layer thickness from 3–300 nm, BaZrO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BZO) layer thickness from 0.5-1.5 nm, and film growth temperature from 775–825 °C. Systematic results of critical transition temperature (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_c</i>) and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c(H,T,Θ)</i> were plotted as function of YBCO layer thickness and BZO addition up to 16 volume % . Optimization of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c(H,T,θ)</i> was found to vary with process parameters from 30–77 K, for example at 77 K flux pinning was optimized for 825 °C process temperature. However, for 30 K operation temperature, flux pinning was much less sensitive to BZO+YBCO film parameters, and slightly optimized for 805 °C process temperature. For all <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H,T</i> conditions studied, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c(H,T)</i> values achieved a maximum peak for BZO = 8–12 volume % additions in close agreement with published models of flux pinning, and required BZO layer thickness < 0.6 nm.