Magnetic behavior of SnO2 nanosheets has been investigated both experimentally and theoretically. It is found that SnO2 nanosheets with a thickness of 1.5–13 nm show ferromagnetic state at ambient temperature. First-principles calculations reveal that oxygen atoms at O-terminated surface in SnO2 sheet are spin polarized, resulting in magnetic moment of 1.6 μB for pure SnO2 nanosheet while Sn atoms just beneath the O-terminated surface contribute only −0.082 μB. This study will stimulate more investigations for understanding the origin of ferromagnetic TM-doped SnO2 (TM=3d transition metals) in particular case and TM-doped semiconductor oxides in general at ambient temperature and trigger further studies for magnetic behavior of low-dimensional systems which are nonmagnetic in bulk state.

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The electronic structures and optical properties of Boron, Carbon or Nitrogen doped BaTiO3 are calculated by the first-principles calculations. The doped atoms decrease the band gap of BaTiO3 significantly, which could increase the host material ability to absorb the visible light. The absorption spectrum calculations confirm that both Boron and Carbon-doped BaTiO3 have a favorable performance in the absorption of visible light. However, Nitrogen-doped BaTiO3 doesn’t present the improvement. BaTiO3 doped with Boron or Carbon is expected to be a new class of perovskite materials for the field of solar energy.