Fe-based alloys with a nanocrystalline-amorphous nanostructure exhibit superior soft-magnetic performances; however they generally suffer from the low magnetization because of their heavy doping for an acceptable manufacturability. In this study, we proposed a revolutionary nanostructureconstruction concept based on preforming dense nuclei in the melt-quenching process with a critical cooling-rate and refining the nano-structure via transient metalloid-rich interfaces. A novel alloy composition of Fe85.5B10Si2P2C0.5 was developed via our multi-metalloid stabilization and critical formability strategies by using a total of only 4.6 wt. % light metalloids. This unique alloy design effort leads to unprecedented magnetic properties with the super-high Bs of 1.87 T and me of 1.0–2.5
104 , which outperform all commercial counterparts and have a high potential to substitute for commercial bulk Si-steels currently used for soft-magnetic applications. This hetero-structuring and lean-alloying strategy provides a paradigm for the next-generation of magnetic materials.