Strong Flux Pinning by Cracks in Films of Superconducting Oxide

Abstract

The possibility of flux pinning by cracks along basal planes in single-crystalline films of a superconducting oxide is theoretically investigated. For a single-crystalline film with thec-axis parallel to a substrate, the transport current can flow along the basal plane without an influence of the cracks, while the cracks act as strong pinning centers that prevent fluxoids from moving along thec-axis due to the Lorentz force. The critical current density in YBaCuO atT=77 K andB=5 T is estimated as 1.7×10¹⁰A/m²in the case of a mean interval of the cracks of 50 nm. This value is larger than that in Nb₃Sn at 4.2 K.