Electronic Structures of Several New Rare-Earth Half-Metallic Ferromagnets SmX (X = O, S, Se, and Te)

Several new rare-earth half-metallic ferromagnets with the NaCl structure, namely SmX (X = O, S, Se, and Te), are found based on the first-principle calculations (LSDA + U). These materials only have spin-up subbands at the Fermi level and their net crystal cell magnetic moments are all 6.00 µB per unit cell, which shows that SmX are potential half-metallic ferromagnets. They have high Curie temperatures (above 1000 K) and stable half-metallicity. The magnetic moments, the electrical conductivity, and the half-metallicity of SmX mainly originate from the spin-polarization of Sm-4f orbitals, which are induced by the strong octahedral crystal field in the ligand complex ML6 consisting of the Sm ion and its six X ion ligands. Six 4f electrons occupy six 4f orbitals of the Sm ion in the high-spin sequence. The main reason is that the splitting energy is lower than the pairing energy of 4f electrons because the 4f orbitals are partly electrostaticly shielded by other electrons outside the 4f orbitals.