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 Co2FeAl 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.