Structural stability and magnetic properties of disordered SmCo_7–xM_x (M = metal) modulated by valence electron structure

SmCo_7–xM_x (M = Cu, Zr, Hf, Si, Ga) intermetallic compounds, with distinctive disordered crystal structure and excellent magnetic performance, are of great importance for application as high-temperature rare-earth permanent magnets. In this study, the relationship between the valence electronic structure, structural stability and magnetic and thermal properties of Sm(Co, M)₇ intermetallic compounds is revealed by using an empirical electron theory of solids and molecules. The structural stability is strongly related to the valence electronic structure that is modulated by doping the third element M into SmCo₇. The calculated bond lengths, magnetic moments and Curie temperatures show good agreement with experimental ones. The magnetic moment and Curie temperature strongly depend on the number of 3d magnetic electrons, and can be modulated by mutual electron transformation between 3d magnetic electron and covalence electron.