Optimizing the composition of (Ce,La)(Co,Fe)₅for permanent magnet applications using density functional theory

In this work, we calculated physical quantities, including the magnetocrystalline anisotropy constant (K_u) and magnetization (M_s), for disordered (Ce,La)(Co,Fe)₅systems. Based on the results, we propose CeCo_4.7Fe_0.3as the optimum composition for high-performance permanent magnets. The calculations employed the full-potential Korringa-Kohn-Rostoker Green's function method, and dealt with the compositional disorder of the systems within the coherent potential approximation. It was found that the La doping reducesK_uat 0 K but increases the Curie temperature (T_C), which leads to improvement of the magnetic properties at high temperatures. CeCo_4.7Fe_0.3had the largest magnetic anisotropy ofK_u= 15.14 MJ/m³, which is larger than that of CeCo₅(K_u= 14.77 MJ/m³).T_Cof CeCo_4.7Fe_0.3estimated by the mean-field approximation was 1005 K, which exceeds that of CeCo₅(965 K). Further, our calculations showed that while doping of Fe destabilizes the system, CeCo_4.7Fe_0.3is stable against decomposition into the simple substances. We also show calculated data that are informative for exploring high-performance permanent magnet materials in this paper.