First-principles study of magnetic properties in Ag-doped SnO2

The electronic structures and magnetic properties of Ag-doped SnO2 have been investigated using first-principles spin-polarized calculations based on density functional theory. Our results demonstrate that Ag doping introduces spin polarization in SnO2 and gives rise to a local magnetic moment of 1.0 µB per substitutional silver ion. The hole-mediated ferromagnetic (FM) coupling between two Ag ions in this material is possibly ascribed to a p–d hopping interaction between O and Ag ions. The oxygen vacancy (VO) plays an important role in determining the magnetic properties of the Ag-doped SnO2 system. It is found that the VO does not induce magnetism in bulk SnO2. The VO enhances stability of the spin-polarized state for the case of the single-Ag-doped system, and imposes an intricate effect on a pair of Ag-doped configurations. For example, the FM coupling between two Ag ions is possibly reinforced if VO is sufficiently far away from them. The result indicates that Ag-doped SnO2 is a promising candidate for applications in future spintronic devices.