CdS:Co diluted magnetic semiconductor nanocrystals: synthesis and ferromagnetism study

A novel method was developed to prepare zinc blende structure CdS:Co diluted magnetic semiconductor nanocrystals. The prepared samples display ferromagnetic behavior with a crystal size of about 3–4 nm. First-principle calculations show the phenomenon of ferromagnetism in CdS:Co nanocrystals arising not only from the Co atoms, but also from the Cd vacancies, with Co atoms being the major contributor. The introduction of Co atoms into CdS significantly reduces the formation energy of Cd vacancies, producing a lot of vacancies which enhance the ferromagnetism of the samples as a whole.