Ab initio GGA+U investigations of the electronic properties and magnetic orderings in Mn, Gd doped ZB/WZ structural CdSe

Abstract In the paper, the electronic properties and magnetic orderings in the Mn/Gd doped zinc-blende (ZB) and wurtzite (WZ) structural CdSe are investigated extensively using first-principles calculations. We find that the infiltration of Mn ions in the ZB/WZ structural CdSe will lead to the antiferromagnetic ordering; while the infiltration of Gd ions will lead to the ferromagnetic ordering. Moreover, the antiferromagnetic/ferromagnetic coupling interactions between the magnetic Mn/Gd ions will become more and more strong with decreasing Mn-Mn/Gd-Gd distance. Particularly, the electronic properties in the Mn mono-doping case (spin-polarized) and in the Mn double-doping case (ferromagnetic) are almost same, and they tend to be the magnetic/ferromagnetic semiconductor via the comparison from the different calculations; as a whole, the Mn doped ZB/WZ structural CdSe system tends to present the antiferromagnetic semiconductor character. In addition, the band gap in the Mn doped ZB/WZ structural CdSe decreases with increasing Mn concentration using GGA+U calculations. In contrast to the case of the Mn doped ZB/WZ CdSe: (i) the Gd doped ZB/WZ CdSe in the mono-doping case displays the magnetic semiconductor character; but the Gd doped ZB/WZ structural CdSe in the double-doping case presents the n-type ferromagnetic semiconductor, and the robust ferromagnetism is obtained in the system irregardless of the crystal structure and the distance between the magnetic ions; (ii) the band gap in the Gd doped ZB/WZ structural CdSe increases with increasing Gd concentration, Burstein-Mott-effect might be major reason.