Interstitial H+-Mediated Ferromagnetism in Co-Doped ZnS

Abstract

The ferromagnetic mediation centers of enough high concentration are the prerequisites for the realization of ferromagnetic diluted magnetic semiconductors. Zn<inf>0.97</inf>Co<inf>0.03</inf>S ultrafine nanoparticles of diameter ˜4 nm with zinc blende structure were synthesized by the chemical coprecipitation method. After annealing in H<inf>2</inf> atmosphere at 500 °C for 2 h, Zn<inf>0.97</inf>Co<inf>0.03</inf>S transformed to wurtzite structure of increased particle size and strongly enhanced room temperature ferromagnetism has been observed. The possible ferromagnetic contribution from metallic Co due to reduction by H<inf>2</inf> has been excluded. Combining the structural characterizations and density functional theory calculations, we conclude that the interstitial H⁺ ions in wurtzite ZnS may provide efficient ferromagnetic mediation between the neighboring Co²⁺ ions.