Magnetization performance of hard/soft Nd_9.6Fe_80.3Zr_3.7B_6.4/α-Fe magnetic nanocomposites produced by surfactant-assisted high-energy ball milling

Neodymium iron boron (NdFeB) magnets are sintered anisotropic materials. They were commercially introduced in the early 1980s, and since have been used in different applications owing to their superior properties. Herein, we investigated the influence of 0.5 to 8 h of milling time on the morphological, structural, and magnetic performance of Nd_9.6Fe_80.3Zr_3.7B_6.4 powders produced using surfactant-assisted high-energy ball milling (SA-HEBM). The results revealed that the relationship between coercivity (H _ci) and milling time had a non-monotonous character reaching a maximum value of H _ci = 8.92 kOe after 1 h of milling. The effect of the volume ratio of various magnetic phases (Nd₂Fe₁₄B and α-Fe) on microstructure and magnetic properties was also reported. The highest specific saturation magnetization (σ _s = 120 emu g⁻¹) was attained after 8 h of milling for powders with volume fraction: Nd₂Fe₁₄B–81 ± 2% and α-Fe–12 ± 2%. The expected value of Nd₂Fe₁₄B specific saturation magnetization was estimated (σ _N = 108 ± 2.5 emu g⁻¹) using the experimental value of σ _s and magnetic phase volume fractions. The ratio of remanence to saturation magnetization of the Nd₂Fe₁₄B with milling time was also determined and analyzed. (paper)