Effects of Oxygen Vacancy on the Magnetic Properties of Ni-Doped SnO2 Nanoparticles

We studied the ferromagnetism of Ni-doped SnO2 with and without oxygen vacancy (VO) by experiments and calculations. Sn0.96Ni0.04O2 nanocrystalline powder prepared by the sol-gel method exhibits room-temperature ferromagnetism, and the vacuum annealing reduces its saturation magnetizations. The density functional theory (DFT) calculations show that the doped Ni atom can introduce a local magnetic moment of about 2.0 μB in SnO2 (110) surface, which is ascribed to the spin-polarization of Ni 3d and O 2p electrons. The type of preferential magnetic coupling of Ni-doped SnO2 (110) surface depends upon the distributions of Ni dopants, and ferromagnetic coupling is more favorable in most cases. Introduction of VO obviously weakens the ferromagnetic interaction of Ni-doped SnO2 (110) surface, which can give a reasonable explanation for our experimental observations.