Permanent Magnets Beyond Nd-Dy-Fe-B

Provision of a concise summary of recent developments of permanent magnet materials and the materials science underlining them toward realizing permanent magnets beyond the current Nd-Dy-Fe-B is attempted, and approaches to solving the remaining fundamental issues are discussed. Focused are two promising groups of materials: the ThMn₁₂-type Fe-rich Sm(Fe_1-xCo_x)₁₂-based materials and the Nd₂Fe₁₄B-based materials. Materials science based on atomistic view of permanent magnet materials specifically developed for this purpose is required in order to break into a precise control of the microstructure in atomic levels with the aid of computational material engineering. Atomistic understandings of coercivity mechanism and differences in free energy associated with formation of non-equilibrium structures such as grain boundaries and interfaces with sub-phases are proposed to be essential.