Magnetic properties of several potential rocksalt half-metallic ferromagnets based on the first-principles calculations

Several rocksalt Sr₄X₃N (X=O, S, Se, and Te) are predicted to be potential half-metallic ferromagnets free of transition-metal and rare-earth elements by performing the first-principles calculations. Then their magnetic properties, such as the half metallicity and the crystal-cell magnetic moments are investigated. The Sr₄X₃N possibly have higher Curie temperatures and have more stable half metallicity than the Sr₄X₃C. Their crystal-cell magnetic moments are all 1.00 μ_B. The crystal-cell magnetic moments and the half metallicity arise mainly from the N ions. The main mechanism is the strong covalent interaction leading to the sp² hybridized orbitals in the Sr₄X₃N. Then two Sr-5s and three N-2p electrons enter into three sp² hybridized orbitals. Among these five electrons, four electrons are paired and one is unpaired, so there are three spin-up electrons and two spin-down electrons in these sp² hybridized orbitals.