Density-functional theory study of half-metallic heterostructures: Interstitial Mn in Si

Using density-functional theory within the generalized gradient approximation, we show that Si-based heterostructures with 1/4 layer δ doping of interstitial Mn (Mn_int) are half-metallic. For Mn_int concentrations of 1/2 or 1 layer, the states induced in the band gap of -δdoped heterostructures still display high spin polarization, about 85% and 60%, respectively. The proposed heterostructures are more stable than previously assumed δ layers of substitutional Mn. Contrary to widespread belief, the present study demonstrates that interstitial Mn can be utilized to tune the magnetic properties of Si, and thus provides a new clue for Si-based spintronics materials