High intergranular critical currents in metallic MgB2 superconductor

Strong evidence for high intergranular critical current densities and large bulk magnetic flux pinning in superconducting polycrystalline MgB2 has bee n observed. The presence of strongly-coupled grain boundaries in this mater ial has been confirmed by a dramatic collapse of the magnetic hysteresis lo op when a bulk specimen is ground into a fine powder and re-measured under similar conditions. Further evidence for strong intergrain links in polycry stalline MgB2 is provided by the continuous variation of the remanent magne tic moment up to the full penetration field of a bulk sample. The absence o f weak-link nature in this material has profound implications for its poten tial in a wide range of engineering applications.