Density-Functional Study On The Ferromagnetism Of Mn-Doped Sno2

So far, both room-temperature ferromagnetism and paramagnetism have been reported in Mn-doped SnO2 films and their magnetic properties remain still puzzling. We have systematically investigated the magnetic properties of Mn-doped SnO2 by first-principles calculations. Our results reveal that the magnetic coupling is too weak and consequently paramagnetism is only found in the doped system when Mn substitutes Sn atoms. The formation energy of Mn impurity is much higher without the presence of vacancy, which prevents their substitutions significantly. In the presence of vacancies, the formation energy of Mn is greatly reduced and they can substitute Sn heavily. Compared to Sn vacancies, oxygen vacancies mediate the ferromagnetism much more effectively. The origin of ferromagnetism in Mn-doped SnO2 can be attributed to the oxygen-vacancy mediated RKKY interaction. (C) 2013 AIP Publishing LLC.