Characterization of 57Fe implanted SnO2 films by Mossbauer spectroscopy and Nuclear Inelastic Scattering

The as implanted sample at room temperature and post-annealed samples did not show Kerr effect, but the sample implanted with 1x1017 Fe ions/cm², heated at 300°C, showed a little Kerr effect although the magnetic sextets were not clearly observed in 57Fe CEM spectra. The Kerr effect disappeared after postannealing. This suggests that the number of magnetic defects decreases by absorption of oxygen [1]. We also showed that the bulk magnetization is enhanced by co-doping of Sb and Fe into SnO2 powder [2]. We have analyzed the nanostructure of SnO2 films doped with 57Fe by conversion electron Mossbauer spectroscopy (CEMS) and nuclear inelastic scattering (NIS) at SPring8. We implanted 57Fe with 5x1016 ions/cm2 into SnO2 films containing 0.1% Sb and 3% Sb at the substrate temperature of 500°C in vacuum. Kerr rotation angles for 0.1% Sb doped SnO2 film were larger than that for 3%Sb doped SnO2 films. The samples post-annealed at 400°C for 6 hours also showed the Kerr effect. DCEM spectra were measured by discriminating conversion electrons with a back scattered type of gas counter [3]. As the results, four subspectra were observed: two doublets are assigned to paramagnetic Fe3+ and Fe2+ species and two broad sextets to site A and site B of magnetite. For 0.1%Sb doped SnO2 films the relative area of the magnetite phase was larger than for 3%Sb doped SnO2 films. After post-annealing, two sextets changed into one broad sextet, which is due to fine maghemite. The ferromagnetic behaviors of Fe implanted tin oxide films were attributed mainly due to the formation of magnetite for the as implanted samples and of maghemite for the post-annealed samples, respectively, rather than magnetic defects.