The role of chemical structure on the magnetic and electronic properties of Co₂FeAl₀.₅Si₀.₅/Si(111) interface

We show that Co₂FeAl₀.₅Si₀.₅ film deposited on Si(111) has a single crystal structure and twin related epitaxial relationship with the substrate. Sub-nanometer electron energy loss spectroscopy shows that in a narrow interface region there is a mutual inter-diffusion dominated by Si and Co. Atomic resolution aberration-corrected scanning transmission electron microscopy reveals that the film has B2 ordering. The film lattice structure is unaltered even at the interface due to the substitutional nature of the intermixing. First-principles calculations performed using structural models based on the aberration corrected electron microscopy show that the increased Si incorporation in the film leads to a gradual decrease of the magnetic moment as well as significant spin-polarization reduction. These effects can have significant detrimental role on the spin injection from the Co₂FeAl₀.₅Si₀.₅ film into the Si substrate, besides the structural integrity of this junction.