Surface effects on the magnetic properties of Co₂FeAl(0 0 1): An ab initio study

Electronic structures of the Co₂FeAl(0 0 1) surface are studied theoretically via first-principles calculations based on density functional theory. It is found that the minority spin band gap at the Fermi level in bulk Co₂FeAl disappears at the surface due to space localization of the states. However, beneath the surface, the density of states of individual atoms shows a trend of minority spin gap opening at the Fermi level, which indicates that the electronic structures become close to that of bulk Co₂FeAl. The termination of FeAl is more favorable for spin polarization of Co ₂FeAl films than that of Co. Accordingly, we present a composite tri-layer model to illustrate the fading of the half-metallic property in Co₂FeAl films against the ideal character in bulk materials.