Half-metallic ferromagnetism in the full-Heusler compounds KCaX2 (X = C, N, and O)

The electronic structure and magnetic properties of the KCaX2 (X = C, N and O) full-Heusler compound are studied on the basis of band-structure calculations, using the state-of-the-art full-potential linearized augmented plane wave (FP-LAPW + lo) method within the generalized gradient approximation (GGA). We found that the KCaC2 has an antiferromagnetic ground state while the ferromagnetic state is more favorable than the antiferromagnetic state for both KCaN2 and KCaO2 and they exhibits half-metallic ferromagnetism, the strong spin polarization of 2p shell for N and O atoms is found to be the origin of ferromagnetic in both compounds leading to a total magnetic moment of 3 and 1μB respectively. The heat of formation obtained for KCaN2 and KCaO2 compounds shows that both are thermodynamically stable and may be prepared experimentally. The spin-up electrons are semiconductor, but the spin-down bands are metallic with a gap of 3.45, 4.12 eV, and the half metallic gap is of 0.16, 0.30 eV respectively.