Simultaneous achievement of high J _cand suppressed J _canisotropy by hybrid pinning in YBa₂Cu₃O₇three-phase-nanocomposite film

Nanoscale pinning centers are introduced into YBa2Cu3O7 (YBCO) films and tapes to improve vortex pinning and critical current density (J c) for coated conductor application. While pinning with a single type of pinning center has been mainly investigated, hybrid pinning with multiple types of pinning center is expected to be more promising for simultaneously achieving high J c values and suppressing J c anisotropy. In the present study, a three-phase-nanocomposite film consisting of an YBCO matrix, BaHfO3 nanorods and Y-O nanoparticles was fabricated. A global pinning force maximum (F p,max, where F p = J c B) of 1.57 TN m-3 at 4.2 K, which is as high as the record level of F p,max, was achieved by the hybrid pinning of BaHfO3 nanorods and Y-O nanoparticles. Furthermore, the hybrid pinning improved the angular dependence of J c. The pinning contribution from nanoparticles increased with lowering temperature, which can explain the high J c at low temperature. Thus, the present study successfully demonstrates a highly effective structure that can simultaneously achieve suppressed J c anisotropy and a record level of J c.