Optimizing magnetic permeability in iron-nickel nanocrystalline powders and spark plasma sintered materials for advanced applications

This study investigates the impact of alloying elements, grain size, particle size, and spark plasma sintering (SPS) on the maximum permeability of iron-nickel nanocrystalline powders. The results show that increasing nickel content generally decreases permeability, except in the case of 50wt% Ni–Fe powder mixtures, where particle size effects dominate. Permeability is found to be grain size-dependent, with a critical grain size range of 20–30 nm, below which single-domain grains form, leading to increased permeability. However, permeability decreases with decreasing particle size, exhibiting a stepped pattern likely due to surface defects. Notably, the 40wt% Ni–Fe SPS sample exhibits a high permeability value of 6.2 × 10^-3 emu/Oe after 32 h of milling, with optimal grain sizes ranging from 425 to 475 nm for 40 and 75wt% Ni–Fe SPS alloys. Article Highlights: