Pinning Efficiency of One-Dimensional Artificial Pinning Centers in YBa2Cu3O7-x Thin Films

Abstract

BaZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BZO) and BaHfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BHO) form the comparable diameter ~5-6 nm of one-dimensional artificial pinning centers (1-D APCs) in 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) film. However, the lattice mismatch ~7.7% at the BZO/YBCO interface is slightly higher than ~7.1% at the BHO/YBCO interface. This leads to a much reduced interface dislocation density and coherent interface at the BHO/YBCO film that has found a critical effect on the pinning efficiency of the 1-D APCs. This paper thus presents a quantitative comparison of pinning efficiency of single doped 4.0 vol.% BZO/BHO (SD) and double doped 4.0 vol.% BZO(BHO) + 3.0 vol.% Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> doped (DD) YBCO films. A significantly higher pinning efficiency in terms of a maximum pinning force density Fp,max ~182 GN/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> > 9.0 T for BHO SD film may be due to coherent interface. This is about 2.5 times higher than that of its BZO SD counterparts at 65 K. In addition, the ratio of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> and H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sup> (accommodation field determined from the areal density of the 1-D APCs using TEM) is calculated about 0.74 and 0.53 for BHO SD and BZO SD films, respectively. This value is about 0.65 and 0.82 for BHO DD and BZO DD films, respectively at 65 K.