Unique behaviour of RE1Ba2Cu3O7-δ superconducting tapes producing drastic reduction of pinning loss

The reduction of flux-pinning loss is a paramount concern for power applications of RE1Ba2Cu3O7-δ (RE: rare earth, Y, Gd, etc; REBCO) superconducting tapes. We have discovered a unique electromagnetic behaviour of such tapes where the magnetization loops in an oblique magnetic field showed a drastic deviation from the conventional theoretical prediction. It brought about a drastic reduction of the pinning loss contrary to common knowledge that pinning loss is proportional to a critical current density. The deviation was enhanced at lower temperatures, at higher magnetic fields, when the applied magnetic field angle to the tape face was smaller, in the tapes with higher critical current densities, and with a higher in-plane alignment of REBCO grains. We also verified this unusual behaviour is intrinsic to REBCO superconducting thin films and inferred the origin lies in the fact that magnetic flux has a tendency to penetrate into, and exude out of, REBCO superconducting films in a direction parallel to the CuO2 planes in its crystal structure. The results suggest the possibility of reducing the pinning loss by improving the in-plane alignment of REBCO grains instead of reducing the geometrical width of superconductors as suggested by the conventional theory.