Multilayer YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>/Ca<sub>0.3</sub>Y<sub>0.7</sub>Ba<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>Nanocomposite Films With 2–8% BaZrO<sub>3</sub>Doping for High-Field Applications
Mohan Panth, Mary Ann Sebastian, Di Zhang, Victor Ogunjimi, Bibek Gautam, Jie Jian, Jijie Huang, Yifan Zhang, Timothy J. Haugan, Haiyan Wang, Judy Wu
Abstract
High-field applications require high concentrations of strong pinning centers. In this article, BaZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> doped 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</sub> (BZO/YBCO) nanocomposite films with BZO doping up to 8 vol.% were fabricated in a multilayer (ML) format by inserting two 10 nm thick Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Ba <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> spacer layers in the BZO/YBCO nanocomposite films for improved pinning and enhanced critical current density <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J<sub>c</sub></i> at high fields. Significant <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J<sub>c</sub></i> enhancement was observed in all the BZO/YBCO ML films of BZO doping in the entire range of 2–8 vol.% as compared to their SL counterpart's. At 65 K, the enhancement of peak pinning force density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F<sub>p,</sub></i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) is 71, 67, 296, and 47% for 2, 4, 6, and 8 vol.% BZO/YBCO ML films, respectively. In addition, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> (the location of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F<sub>p,</sub></i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) is shifted towards higher values for BZO/YBCO ML films by up to 33%. Interestingly, at high BZO doping of 8 vol.%, the enhanced modulated strain field was found to reduce the detrimental effect of Ca ion diffusion on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , leading to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J<sub>c</sub></i> enhancement at a strong field up to 9 T at all orientations of the magnetic field.