First principle calculations on electronic, magnetic and optical properties of Mn doped and N co-doped CdS

In this work, we investigate the electronic, magnetic, and optical properties of wurtzite CdS doped with Mn at the cation site and co-doped with N at the anion site using the first principle calculations. We find that the Mn doping induces a magnetic ground state with the total magnetic moment of 5 μ_B. The antiferromagnetic interaction between two Mn ions is discussed on the basis of the super-exchange mechanism. Presence of the p-type dopants, such as N, at S site makes a great effect on the magnetic ground state of the Mn doped CdS system. The p-type defects stabilize the ferromagnetic ground state. Furthermore, the optical absorption spectra are discussed for pure CdS, Mn-doped CdS and N co-doped (Cd, Mn)S. The Mn doping causes a red shift of the optical spectrum. The N co-doping of (Cd, Mn)S lays in the origin of a new peak in infrared region, due to the defect states. We correlate the d-d optical transition with the magnetic interactions between the Mn ions. The d-d peaks in the calculated optical spectra are blue shifted in the AFM phase and red shifted in FM phase, which is consistent with the experimental data.