Nb-doping Induced High Coercivity in Pr<sub>2</sub>Fe<sub>14</sub>B/α-Fe Nanocomposite Melt-spun Ribbons

The effect of niobium (Nb) doping on the microstructure and magnetic properties of as-spun Pr10Fe82.5-xB6.5Nbx ribbons was investigated. Nb doping significantly refines the grain size and enhances the coercivity, which increases from 380 kA/m (x = 0) to a remarkable 990 kA/m (x = 3), a top-level performance among Nb‑doped rare-earth-deficient nanocomposite alloys. The improvement is attributed to the microstructural refinement and a shift in the magnetization reversal mechanism toward dominant domain‑wall pinning. Recoil loop measurements further confirm that Nb doping strengthens the intergranular exchange coupling. This work demonstrates that Nb doping is a feasible and efficient approach for producing cost-effective, high-performance permanent magnets with low rare-earth content.