Ab initio studies of Co2FeAl1−xSix Heusler alloys

•GGA+U calculations: μ and Eg dependence on the value of U for Co2FeAl and Co2FeSi.•Behavior of magnetic hyperfine fields on the Co site of Co2FeAl1−xSix versus x.•DFT proof of suppression of formation of antisites defects with x in Co2FeAl1−xSix.

We present results of extensive theoretical studies of Co2FeAl1−xSix Heusler alloys, which have been performed in the framework of density functional theory employing the all-electron full-potential linearized augmented plane-wave scheme. It is shown that the Si-rich alloys are more resistive to structural disorder and as a consequence Si stabilizes the L21 structure. Si alloying changes position of the Fermi level, pushing it into the gap of the minority spin-band. It is also shown that the hyperfine field on Co nuclei increases with the Si concentration, and this increase originates mostly from the changes in the electronic density of the valence electrons.