Fig. 3: Electrical resistivity, thermal stability, and magnetic properties of the MOS.

a The electrical resistivity (ρ) of the MOS-S compared to its constituents α-Fe and Nd₂Fe₁₄B. Error bars represent the range of ρ. b Comparison of the ρ of the MOS-S, homo-structure (HS) with the same composition, gradient structures (GS) Nd₂Fe₁₄B, GS Nd₂Fe₁₄B/α-Fe (both without the sandwich core-shell structure), single crystal (S.C.) NdFeB, commercial (Comm.) SmCo₅, Sm₂Co₁₇ and NdFeB. Error bars represent the range of ρ. c Comparison of the thermal stability of H_c among the MOS, commercial NdFeB, untreated NdFeB, and NdFeB treated by grain boundary diffusion process (GBDP) and alloying. The thermal stability of H_c is designated as 1/|β|, where β is the temperature coefficient of H_c. d Comparison of the ρ and 1/|β| of the MOS and the state-of-the-art commercial performances, including SmCo₅, Sm₂Co₁₇ and NdFeB. Error bars represent the range of ρ and 1/|β|. e Plot of B_r and H_c of the MOS, GS Nd₂Fe₁₄B, GS Nd₂Fe₁₄B/α-Fe and NdFeB based nanocomposite magnets prepared by various methods, including melt spinning (MS), high-pressure torsion deformation (HPTD) and amorphous alloys annealing (ANN). f The changes in (BH)_max and ρ in the MOS fabricated using the FASA method compared to NdFeB magnets prepared by GBDP and NdFeB composite magnets with Dy₂O₃, NdF₃, CaF₂ and SiO₂. The data for comparison are derived from literature, see Supplementary Tables 3−7.