Half-metallic ferromagnetic features in d0 quaternary-Heusler compounds KCaCF and KCaCCl: A first-principles description

The electronic structures and magnetic properties of quaternary Heusler alloys KCaCF and KCaCCl have been analyzed by means of first-principles calculations on the basis of density functional theory. We found that type-3 structure is the most stable configuration where C occupies (0, 0, 0) site, K (0.25, 0.25, 0.25), F/Cl (0.5, 0.5, 0.5), and Ca (0.75, 0.75, 0.75). Type-1 arrangement is the metastable structure in which K, Ca, C, and X occupy (0, 0, 0), (0.25, 0.25, 0.25), (0.5, 0.5, 0.5), and (0.75, 0.75, 0.75) sites, respectively. Both of them are half metals with equilibrium volume. The spin polarization is predominantly from C 2p states. With the variation of the lattice constant, spin-gapless semiconducting characteristic is achieved for type-1 KCaCCl as volume increases.