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.