Ab initio study of electronic structure and magnetic properties of CoMnTaZ (Z = Si, Ge) quaternary Heusler compounds

The electronic structures and magnetic properties of CoMnTaSi and CoMnTaGe Heusler alloys with LiMgPbSb-type structure investigated firstly by using the first-principles calculations. We have applied the full-potential linearized augmented plane waves plus local orbitals (FP-L/APW+LO) method. Exchange-correlation effects are treated using the generalized gradient approximations GGA and GGA+U. The GGA calculation shows the CoMnTaSi and CoMnTaGe compounds at its equilibrium lattice constant are HM ferromagnet with an indirect band gap Γ → X of 0.34 and 0.39 eV and a HM gap of 0.34 and 0.13 eV in the spin-down channel. The CoMnTaZ (Z = Si, Ge) compounds have an integer total magnetic moment of 1.00 μB, satisfying the Slater–Pauling rule mtot = (Nv − 24). The similar results are also obtained by GGA+U calculation. Therefore, these new materials are good candidates for potential applications in spintronic.