First-principles calculations on the surfaces and interfaces of SmFe₁₂

Nd-Fe-B sintered magnets are currently used in a wide range in industry. However, it is seriously problematic that the coercivity of Nd-Fe-B sintered magnets significantly decreases at high temperatures. In contrast, a new magnetic compound SmFe₁₂ has a higher magnetic anisotropy than Nd₂Fe₁₄B which is the main phase of Nd-Fe-B sintered magnets. Therefore, SmFe₁₂-based magnets can be expected as a preferable alternative of existent magnets. The performance of magnets is strongly influenced by microstructural interfaces. However, there are few studies about interfaces including SmFe₁₂.

We performed first-principles calculations on the surfaces and interfaces of Nd₂Fe₁₄B and SmFe₁₂, and analyzed the structural stability and magnetic properties. The surface energies of SmFe₁₂ and Nd₂Fe₁₄B are examined to find the most stable surfaces. Then, the interface of SmFe₁₂ with a subphase is constructed using the most stable surface structures. For stable interface structures, the magnetic properties are examined, where the magnetic moment of Fe is enhanced around the interface of SmFe₁₂/SmCu. We will also present the results on the magnetic anisotropy and the magnetic coupling at SmFe₁₂-based interfaces.