First-principles study on half-metallic properties of the CoMnZ (Z = S, Se, Te) half-Heusler compounds

•CoMnTe is predicted to be half-metallic ferromagnet.•CoMnS and CoMnSe compounds are nearly half-metallic.•All compounds have a total magnetic moment of 4 μB/f.u.•The spin-down bands of CoMnTe are semiconductor with a gap of 1.04 eV.•The spin-flip gap CoMnTe is of 0.37 eV.

The first-principles calculations based on the density functional theory have been employed to explore the electronic structure and magnetic properties of the CoMnZ (Z = S, Se, Te) half-Heusler compound. CoMnTe is predicted to be half-metallic ferromagnet with an energy gap of 1.04 eV in the minority spin and a completely spin polarization at the Fermi level. CoMnS and CoMnSe compounds are nearly half-metallic with spin polarization of 98.9 and 97.9%, respectively. All compounds have a total magnetic moment of 4 μB/f.u., which agrees with the Slater–Pauling rule. CoMnTe compound keeps half-metallicity within a wide range of lattice constants between 5.65 and 6.05 Å. Under tetragonal distortions, high spin polarization at the Fermi level is maintained for the CoMnTe compound.