Objective 2. Synthesis of nanocomposite magnets via “epitaxial-like” growth of L1₀ FeCo on L1₀ FePt or CoPt nanoparticles in liquid phase reactions.

This objective includes for the first time the synthesis of nanocomposite hard magnetic materials based on traditional L1₀ FePt and CoPt nanoparticles coated with L1₀ FeCo shells. The main advantage of these nanocomposite magnets, that we propose here, is that both core and shell parts of the nanostructured particles contribute simultaneously to the magnetocrystalline anisotropy and the saturation magnetization, in contrast with the heavy diamagnetic L1₀ CuAu and as a result it affects the energy product of the overall material (see state of the art section). Additionally, the Pt content will be significantly decreased in the final composites core/shell particles. We estimate the Pt content to decrease from 50 at. % in the L1₀ FePt alloys, to less than 25 at. % in the L1₀ nanocomposite core/shell particles. To achieve this we propose the synthesis of L1₀ FePt at the smallest nano-size possible, (<20 nm), maximizing the surface area for the epitaxial growth of L1₀ FeCo shells. The L1₀ FePt nanoparticles that will used as seeds will have >1 T, room temperature coercivity, leading to nanocomposite core/shell particles with Hc in the range of 0.4-0.8 T. The PI has already experience on the synthesis of L1₀ FePt and CoPt nanoparticles directly in liquid phase with 15.2 kOe room temperature coercive field in the 20 nm diameter size regime.¹⁴