Transformational Dynamics of BZO and BHO Nanorods Imposed by Y2O3 Nanoparticles for Improved Isotropic Pinning in YBa2Cu3O7-Delta Thin Films

An elastic strain model was applied to evaluate the rigidity of the c-axis aligned one-dimensional artificial pinning centers 1D-APCs in YBa2Cu3O7-delta matrix films. Higher rigidity was predicted for BaZrO3 1D-APCs than that of the BaHfO3 1D-APCs. This suggests a secondary APC doping of Y2O3 in the 1D-APCYBa2Cu3O7-delta nanocomposite films would generate a stronger perturbation to the c-axis alignment of the BaHfO3 1D-APCs and therefore a more isotropic magnetic vortex pinning landscape. In order to experimentally confirm this, we have made a comparative study of the critical current density Jc H, theta, T of 2 vol. BaZrO3 3 vol. Y2O3 and 2 vol. BaHfO3 3 vol. Y2O3 double-doped DD YBa2Cu3O7-delta films deposited at their optimal growth conditions. A much enhanced isotropic pinning was observed in the BaHfO3 DD samples. For example, at 65 K and 9.0 T, the variation of the Jc across the entire theta range from theta0 Hc to theta90 degree Hab is less than 18 for BaHfO3 DDfilms, in contrast to about 100 for the BaZrO3 DDcounterpart. In addition, lower alpha values from the JcH similar to H-alpha fitting were observed in the BaHfO3 DD films in a large theta range away from the Hc-axis. Since the two samples have comparable Jc values at Hc-axis, the improved isotropic pinning in BaHfO3 DD films confirms the theoretically predicted higher tunability of the BaHfO3 1D-APCs in APCYBa2Cu3O7-delta nanocomposite films. C 2017 Authors.