Electronic structure and magnetic properties of metastable SmCo7 compound

Abstract

The electronic density of states, spin-splittings and atomic magnetic moments of SmCo7 compound have been studied using spin-polarized MS-Xa method. The results show that a few of electrons are transferred to Sm(5d0) orbital because of orbital hybridization between Sm and Co atoms in the compound. The exchange interactions between 3d and 5d electrons lead to the magnetic coupling between Sm and Co, and therefore, result in the long-range ferromagnetic order inside the SmCo7 compound. There are negative exchange couplings occurring at some levels, which weakens the strength of average coupling around Co lattice. So, the Curie temperature and Co-moment of SmCo7 decrease distinctly compared with pure Co. Compared with SmCo5 compound, the disordered substitution of Co-Co “dumbbell-atom” pairs for Sm changes the local environment of Co lattice, which makes the 2e site bear negative magnetic moment. The strength of hybridization near Fermi level weakens and the free energy of the compound increases obviously. Thus, SmCo7 is a metastable compound at room temperature. Considering the localization of 4f electrons and a few of 5d electrons arising from the orbital hybridization, the magnetic moment of Sm atom will be 1.61 μ B in SmCo7 compound, which is in agreement with the experimental values of Sm3+ ionmoment and Sm atom-moment in metals.