Robust half-metallic ferromagnet of quaternary Heusler compounds ZrCoTiZ(ZÂ =Â Si, Ge, Ga and Al)

A first-principles approach is used to study the structural, electronic and magnetic properties of ZrCoTiZ(Z = Si, Ge, Ga and Al) quaternary Heusler compounds, using full-potential linearized augmented plane wave (FP-LAPW) scheme within the GGA. Our calculations predict that ZrCoTiSi, ZrCoTiGe, ZrCoTiGa and ZrCoTiAl are half-metallic ferromagnets (HMFs) with a HM flip gaps of 1.03, 0.90, 0.68 and 0.59 eV, respectively. The half metallicity is found to be robust with respect to the lattice compression and is maintained up to the lattice constant contraction of 6%, 7%, 9% and 8% for ZrCoTiSi, ZrCoTiGe, ZrCoTiGa and ZrCoTiAl respectively. These compounds show a Slater-Pauling behavior and the total spin magnetic moment per unit cell (mtot) scales with the total number of valence electrons (Nv) following the rule mtot = Nv − 18. The formation enthalpies for both structures are negative indicating stability of these systems against decomposition into stable solid compounds.