Origin of ferromagnetism of Co-doped SnO2 from first-principles calculations

The origin of the ferromagnetism in Co-doped SnO2 is investigated by density functional theory using local spin density approximation plus Hubbard U scheme. Our results show that O vacancy plays a key role in determining the magnetic order in Co-doped reduced samples. The presence of O vacancy makes the Co 3d-t2g minority-spin state broadened, and therefore a t2g-VO hybrid level near the conduction band minimum forms, which results in a strong carrier-mediated ferromagnetic interaction. This suggests a recipe tailoring the magnetic properties of spintronic materials by controlling the intrinsic defects.