First-principles study of antisite defects effect on electronic and magnetic properties of Mn2+xCo1−xGa

• Structural-phase of Mn2+xCo1−xGaMn2+xCo1−xGa transition from a cubic lattice to a tetragonal one occurs for the composition x=0.5.
• The perfect Mn2CoGa is half-metallic and the half-metallic character are preserved for x=0.25 and x=0.5.
• Antisite defects of type(i) can maintain the half-metallic while type(ii) is found to destroy the half-metallic.
• The reduction of the magnetic moment mainly arises from weaker magnetic interactions of Mn and Co for higher Mn concentrations.
• The magnetic interactions are further weakening in the antisite defect models.

The electronic structures and magnetic properties are reported for Mn2+xCo1−xGa (x=0.0, 0.25, 0.5) and Mn2.25Co0.75Ga with antisite defects (AS) using first-principles density functional theory within the generalized gradient approximation (GGA) schemes. Electronic band structure calculations indicate that the perfect Mn2CoGa is half-metallic and the half-metallic character is preserved for x=0.25 and x=0.5. AS defects of type(i) can maintain the half-metallic while AS defects of type(ii) are found to destroy the half-metallic and show metallic behavior. Based on the magnetic property calculations, the experimentally observed reduction of the magnetic moment mainly arises from weaker magnetic interactions of Mn and Co for higher Mn concentrations and the magnetic interactions are further weakening in the AS defect models.