Ab initio exploration of d 0 digital magnetic heterostructures: the case of MgO and CaO δ -doped with potassium

Previous studies of digital magnetic heterostructures have mainly focused on 3 d transition metal δ -doped semiconductors. In this work, sp- electron digital magnetic heterostructures without magnetic ions are proposed. Based on a theoretical density functional investigation, electronic structures and magnetic properties of MgO and CaO δ -doped with K were reported. The results show that these heterostructures are half-metallic ferromagnetic materials having semiconducting up spins and metallic down spins, with an exchange interaction much stronger than that of a random alloy with similar K concentration. Our first-principles calculations show that the carriers at the Fermi level are strongly confined within a few monolayers around the KO plane. This strong confinement is responsible for the large exchange coupling and the two-dimensional half-metallic behavior. The thickness of the host semiconducting spacer does not significantly change the global electric and magnetic features.