Study of ferromagnetism in Bi2S3 and ZnS nanocrystalline powders

Results of magnetic measurements suggested that Bi₂S₃ and ZnS nanocrystalline powders prepared by hydrothermal method could possibly exhibit room temperature ferromagnetism. The measured saturation magnetization of the powders increases with an increase of annealing temperature from 300 to 500 °C. Ab initio calculations suggested that the cation vacancies on the surface of Bi₂S₃ and ZnS nanograins could be responsible for the observed magnetic moments. Heat-treatment of Bi₂S₃ or ZnS nanocrystalline powders in Bi or Zn vapor could bring about an enhancement of ferromagnetism. The calculation results indicated that the interstitial Bi or Zn atoms in Bi₂S₃ (0 0 1) or ZnS (0 0 1) surface could induce magnetic moments.