Magnetic Properties, Heisenberg Exchange Interaction, and Curie Temperature of CdS Nanoclusters

In recent years the magnetism demonstrated in undoped oxide and sulfide semiconductor nanoparticles was intensively studied for the potential applications in nanoscale science. First-principles calculations were performed to investigate the magnetic properties, Heisenberg exchange interaction, and Curie temperature (T_c) of cadmium sulfide (CdS) nanoclusters (NCs) in this work. Our calculations indicate that spin-polarized states are always energetically favorable and that the induced magnetism mainly originates from the dangling bond spins of those two-coordinate S anions located on the S-terminated surface, which is perpendicular to c-axis. Meanwhile, the CdS NCs driven magnetism can be completely destroyed with hydrogen passivation. The calculated Heisenberg exchange interaction and T_c show oscillatory behaviors. The Hubbard model theory can be used to account for the interactions between the dangling bond spins in CdS NCs. These results suggest that CdS NCs may be a promising material for nanoscale magneto-optical devices.