Electronic Structure and Ferromagnetism in Zincblende Zn 1 − x Co x S Nanoparticles

We have prepared Zn1−xCoxS nanoparticles (NPs) and studied their local-geometric, electronic, and magnetic properties. X-ray diffraction analyses have indicated that NPs with average crystallite sizes of 2.2 ∼ 2.9 nm are single phase and crystallize in the zincblende-type structure. Cobalt ions with oxidation state + 2 (Co2+) replaced for Zn2+ and almost unchanged the zincblende-type structure of the ZnS host lattice. Interestingly, all samples show room-temperature ferromagnetism and ferromagnetic order increases with increasing Co content (x) in Zn1−xCoxS NPs. With the results obtained from analyzing the local-geometric structures at Zn and Co K-edges and photoluminescence spectra, we believe that ferromagnetism in Zn1−xCoxS NPs is related to intrinsic defects and exchange interactions between Co2+ ions. We have also reviewed the recent studies on ZnS-based dilute-magnetic materials.