Core-shell-core nanoparticles of an iron-cobalt alloy core, a silica shell and a manganese bismuth alloy core or nanoparticle on the surface of the silica shell (FeCo/SiO2/MnBi) are provided. The core-shell-core nanoparticles are alternative materials to rare-earth permanent magnets because of the hard magnetic manganese bismuth in nanometer proximity to the soft magnetic iron cobalt.
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