Using density-functional theory within the generalized gradient approximation, we show that Si-based heterostructures with 1/4 layer $\delta$-doping of { \em interstitial} Mn (Mn$_{ \mathrm int}$) are half-metallic. For Mn$_{ \mathrm int}$ concentrations of 1/2 or 1 layer, the states induced in the band gap of $\delta$-doped heterostructures still display high spin polarization, about 85% and 60%, respectively. The proposed heterostructures are more stable than previously assumed $\delta$-layers of { \em substitutional} Mn. Contrary to wide-spread belief, the present study demonstrates that { \em interstitial} Mn can be utilized to tune the magnetic properties of Si, and thus provides a new clue for Si-based spintronics materials.
Categories: cond-mat.mtrl-sci
