Magnetic stability of SnO₂ nanosheets.

Room temperature ferromagnetism has been observed in freshly synthesized and post-annealed SnO₂ nanosheets. The results of x-ray diffraction and x-ray photoelectron spectroscopy reveal that the newly synthesized samples and those annealed at 400 °C under either an O₂ or Ar atmosphere possess rutile structure and no other impurity phases are observed. The fitting results of the O 1s and Sn 3d spectra from SnO₂ samples annealed at 400 °C under an O₂ or Ar atmosphere both indicate that oxygen vacancies inevitably exist in these samples. It is found that the saturation magnetization of all the annealed samples does not feature mono-dependence on oxygen vacancies, whereas an Sn vacancy related origin seems more plausible to account for variations in the magnetization of samples studied. This finding corresponds to first-principle calculation results from our previous work. Furthermore, the Curie temperature of SnO₂ nanosheets was estimated to be around 300 °C, rendering it a very good option for the next generation of spintronics.