Electronic structure and magnetic properties of SmCo7?xTix

Electronic structure of SmCo_7−x Ti_x alloy has been studied by means of the spin-polarized MS-Xα method. It is shown that a few of electrons are transferred to Sm(5d) orbital due to orbital hybridization between Sm and Co atoms. The exchange interaction between 5d-3d electrons is stronger, which is the main reason resulting in the long-range ferromagnetic order between Co and Sm atoms. The Curie temperature of SmCo_7−x Ti_x is generally lower than that of pure Co metal, which may be explained by the weaker average of coupling strength between Co sites due to some negative exchange couplings occurring mainly at 2e site. The calculated results for the Sm₅Co₂₈Ti₆ cluster may lead to a better understanding of why SmCo_7−x Ti_x is stable phase. Since the negative interaction of 2e sites weakens and the bonding at E _F strengthens with increasing Ti concentration, which result in the decrease in the free energy of the alloy, the stable ferromagnetic order forms inside SmCo_7−x Ti_x. Considering the localization of 4f states and 5d moment arising from the orbital hybridization, the calculated moment is 9.47 μ _B per formula unit that is in agreement with experiments.