Nanostructured compact bulk MgB2 cryo-magnets with record-high critical currents and trapped magnetic fields

We report a significant breakthrough in enhancing the performance of MgB₂ superconductors by engineering novel nanoscale defects using spark plasma sintering (SPS). By incorporating nanoscale MgB₂O particles via silver addition, carbon doping, and magnesium excess, we introduce a transformative approach to defect design. This innovation yields exceptional material performance, characterized by a self-field critical current density (J_c) of 1.2 MA/cm² at 10 K, a single peak in the normalized pinning force density diagram [f(b) = F/F_max(B/B_irr)] at b = 0.3, and the exceptional trapped field values of 4.21 T at 11 K (for a 20 mm diameter and 5.5 mm thick single MgB₂ bulk), and 5 T at 15 K and 6 T at 10 K of a triple-stacked compact bulk MgB₂ cryo-magnet. These remarkable advancements highlight a novel paradigm in nanoscale defect engineering, with far-reaching implications for superconductors, nanomaterials, and advanced energy systems.