Search for ferromagnetism in SnO2 doped with transition metals (V, Mn, Fe, and Co)

Based on first-principles calculations, we have investigated electronic structures and magnetic properties of SnO2 doped with V, Mn, Fe, and Co. Our results show that ferromagnetism is the ground state and that the Curie temperatures are expected to have high values for Fe-and Co-doped SnO2, which is in good agreement with the experimental observations (Ogale et al 2003 Phys. Rev. Lett. 91 077205; Coey et al 2004 Appl. Phys. Lett. 84 1332). However, in V-and Mn-doped SnO2, paramagnetism is more stable than ferromagnetism. In addition, we also probe the effect of an oxygen vacancy. The results exhibit that an oxygen vacancy strongly influences the magnetic properties of these doped systems, and an oxygen vacancy strongly attracts Fe and Co ions. As a result, transition metal-oxygen vacancy-transition metal groups will be common in Fe-and Co-doped SnO2, but this tendency does not exist in the cases of V and Mn doping. In V-doped SnO2, ferromagnetism becomes more stable than antiferromagnetism after inducing additional n-type carriers and the Curie temperature increases with increasing density of n-type carriers. Hence, raising the density of n-type carriers is a practical way to realize high Curie temperatures in V-doped SnO2.