Nd₂Fe₁₄B/FeCo Core-Shell Nanoparticle Synthesis Using Galvanic Substitution Based Electroless Plating

Core-shell structured magnetic nanoparticles combine hard and soft phases to improve energy efficiency. The mutual interaction of the two phases can lead to the exchange spring effect, leading to higher magnetic energy. In this regard, synthesis of Nd₂Fe₁₄B-based core-shell-structured powders have proven to be elusive, due to the relatively reactive nature of this phase. In this study, a process has been established for successfully coating the surface of Nd₂Fe₁₄B powders with a FeCo layer using the galvanic displacement method. Initially, a binary phase magnetic powder was synthesized containing Nd₂Fe₁₄B and Nd₂Fe₁₇ phase. Subsequently, the powders were coated using a Co precursor at 303 K. During coating, the metastable Nd₂Fe₁₇ phase was dissolved, and the Fe ions were released into the solution. Subsequently, the Fe ions deposited together with the Co ions on the surface of Nd₂Fe₁₄B powder to form a FeCo shell. The deposited layer thickness and composition was confirmed using TEM analysis.