Strong evidence for high intergranular critical current densities and large bulk magnetic flux pinning in superconducting polycrystalline MgB2 was observed. The presence of strongly-coupled grain boundaries in this material was confirmed by a dramatic collapse of the magnetic hysteresis loop when a bulk specimen was ground into a fine powder and re-measured under similar conditions. Further evidence for strong inter-grain links in polycrystalline MgB2 was provided by the continuous variation of the remanent magnetic moment up to the full penetration field of a bulk sample. The absence of a weak-link nature for this material had profound implications for its potential use in a wide range of engineering applications.

High Intergranular Critical Currents in Metallic MgB2 Superconductor. M.Kambara, N.H.Babu, E.S.Sadki, J.R.Cooper, H.Minami, D.A.Cardwell, A.M.Campbell, I.H.Inoue: Superconductor Science and Technology, 2001, 14, L5-7