Coercivity enhancement in Ce-Fe-B based magnets by core-shell grain structuring

Abstract

Ce-based R₂Fe₁₄B (R= rare-earth) nano-structured permanent magnets consisting of (Ce,Nd)₂Fe₁₄B core-shell grains separated by a non-magnetic grain boundary phase, in which the relative amount of Nd to Ce is higher in the shell of the magnetic grain than in its core, were fabricated by Nd-Cu infiltration into (Ce,Nd)₂Fe₁₄B hot-deformed magnets. The coercivity values of infiltrated core-shell structured magnets are superior to those of as-hot-deformed magnets with the same overall Nd content. This is attributed to the higher value of magnetocrystalline anisotropy of the shell phase in the core-shell structured infiltrated magnets compared to the homogeneous R₂Fe₁₄B grains of the as-hot-deformed magnets, and to magnetic isolation of R₂Fe₁₄B grains by the infiltrated grain boundary phase. First order reversal curve (FORC) diagrams suggest that the higher anisotropy shell suppresses initial magnetization reversal at the edges and corners of the R₂Fe₁₄B grains.