Electronic structures and ferromagnetism of SnO2 (rutile) doped with double-impurities: First-principles calculations

The electronic and magnetic properties of double-impurities-doped SnO2 (rutile) are explored using first-principles calculations within the generalized gradient approximation to examine their potential use as spintronic system. Calculations are performed for double impurities (M1 and M2) from M1 = Cr, and M2 = Mn, and Re. The origins of ferromagnetism are shown to be different in the two cases. For Sn1-2xCrxMnxO2, the hybridization between Cr-3d and O-2p results in Cr becoming ferromagnetic with a magnetic moment of about 5.0 μB per supercell. The Cr-and Mn-doped SnO2 system exhibits half-metallic ferromagnetism. The strong ferromagnetic couplings between local magnetic moments can be attributed to p-d hybridization. In contrast, in (Cr, Re) codoped TiO2, the local magnetic moments of the impurities and their oxidation states agree with the charge transfer between Cr and Re, which would lead to the ferromagnetic through the double-exchange mechanism in transition metal oxides. Since there are two possible couplings between the impurities, we studied both configurations (ferromagnetic and antiferromagnetic (AF)) for double-impurities-doped SnO2. Our calculations show that a ferromagnetic alignment of the spins is energetically always more stable than simple AF arrangements, which makes these materials possible candidates for spin injection in spintronic devices.