Comparison of J_c measurements obtained by magnetisation and transport methods for a GdBCO-Ag bulk

Accurate numerical modelling of bulk rare-earth barium cuprate ((RE)BCO) high-temperature superconductors requires measured data of the temperature and magnetic field dependence of the critical current density, J_c, and flux-flow exponent, n. However, there is limited published J_c and n data for modern (RE)BCO bulks. In this work, transport and magnetisation methods were applied to characterise J_c, n, and the critical temperature, T_c, of a commercially available top-seeded melt growth (TSMG) GdBCO-Ag bulk. Both measurement methods exhibit good quantitative and qualitative agreement when the transport electric field criterion is scaled from 1 μV/cm to 10⁻⁴ μV/cm. Transport-derived thermo-magneto-angular dependent J_c data for the TSMG GdBCO-Ag bulk are compared to equivalent data for a SuNAM SCN12700 GdBCO coated-conductor tape. Significant qualitative differences are observed between the data for the bulk and tape, with the tape data featuring neither a fishtail effect nor a B ∥ c peak, both of which are present in the bulk data. A reliable sample preparation and mounting method is presented, which enables the transport characterisation of (RE)BCO bulk superconductors over a large range of temperatures and applied field magnitudes and angles. All J_c and n data presented within this manuscript are available in the Supplementary Material, and can be interpolated into finite-element models to more accurately capture the superconducting behaviour of GdBCO superconductors.