Investigation of structural, magnetic and electronic properties of CoMnSb superstructure: A DFT study

Abstract

Using density functional theory (DFT) based electronic structure calculations, we have investigated the structural, magnetic and electronic properties of CoMnSb superstructure, to elucidate its physical properties and judge its suitability for device applications. We find that the fully optimized CoMnSb superstructure exhibits half metallicity in the bulk ordered structure with a half metallic gap of width ~0.22 eV and a total spin magnetic moment of 3.75 μB/f.u. (120 μB/unit cell). Furthermore, we have studied the role of intrinsic defects (anti-sites and atomic swaps) and strains (uniform and bi-axial) on the half metallic property of the superstructure. We find that the crystal structure of CoMnSb superstructure is stable against intrinsic defects and half metallicity is preserved for a few type of Co(Mn) atomic swap and anti-site defects. It is also observed that, half metallicity is retained for compressive uniform strain up to -3.0% and bi-axial strain up to -3.2%. As the width of the half metallic gap increases for isotropic strain and decreases for bi-axial strain, the former is a better choice for applications. We find that in a fully strained epitaxial thin film of CoMnSb superstructure deposited on GaAs(111) surface, half metallicity is expected to be retained, with the Ef lying within the gap. This condition is technologically more suitable compared to the unstrained condition, where the Ef lies at the top of the valence band.