Composition- and oxidation-controlled magnetism in ternary FeCoNi nanocrystals

Ternary FeCoNi metallic nanostructures have attracted significant attention due to their high saturation magnetization, unique mechanical properties, and large corrosion resistance. In this study, we report a controlled synthesis of ternary FeCoNi nanocrystals using solution-based epitaxial core–shell nanotechnology. The thickness and stoichiometry of the FeCoNi nanocrystals affect their magnetic characteristics, which can be controlled by a phase transformation-induced tetragonal distortion. Furthermore, surface oxidation of the stoichiometry-controlled FeCoNi nanostructures can drastically enhance their magnetic coercivity (up to 8, 881.6 Oe for AuCu–FeCo), and optimize the AuCu–FeCo_0.8Ni_0.2 performance corresponding to the saturated magnetization of 134.4 emu·g^-1 and coercivity of 4, 036.7 Oe, which opens the possibility of developing rare-earth free high energy nanomagnets.