Overcoming optimization constraint for J _c by hybrid pinning in YBa₂Cu₃O₇ films containing nanorods

Abstract Critical current density (J c) in YBa2Cu3O7 films are improved by nanorods. J c increases with increasing the nanorod content up to an optimum content, and decreases after exhibiting a maximum due to degradation of the nanorod structure. To overcome this optimization constraint, hybrid pinning consisting of multiple types of pinning centers was investigated. In the present study, Y2O3 nanoparticles were additionally introduced into the YBa2Cu3O7 films containing high density BaHfO3 nanorods to increase the effective matching field. As a result, the global pinning force maximum was shifted to high magnetic field, and the J c was improved especially in high magnetic field. Thus, even in the case that the J c improvement in the YBa2Cu3O7 + BaHfO3 was difficult by increasing the nanorod content, the Y2O3 addition successfully improved the J c. This demonstrates that the hybrid pinning can overcome the optimization constraint for J c in the YBa2Cu3O7 films containing nanorods.