Ferromagnetic Half-Semiconductor (HSC) gaps in co-doped CdS: Ab-initio study

In this work we have used the density functional theory (DFT) to study structural, magnetic and electronic properties of Co doped CdS in the zinc-blende (ZB) phase. Three approximations have been used to treat the exchange-correlation potential: the (PBE) GGA, (PBE) GGA+U and the model of Tran-Blaha modified Becke-Johnson potential (TB-mBJ). The on-site Coulomb interaction correction given by the Hubbard U has been calculated by the local density approximation constraint for the Co electronic orbitals. The theoretical results show that all the properties under study are affected by the doping of Co atom. Co doped CdS becomes a Ferromagnetic Half-Semiconductors (HSC). The total magnetic moment increases with increasing Co concentration; reaching the value of 9 (in the units of Bohr magneton) at high concentration (x = 18.75 %). The total magnetic moment value is an integer in the GGA+U and TB-mBJ approximations. Furthermore, to validate the effects resulting from the exchange splitting process, we have calculated the values of the spin-exchange constants N-0 alpha and N-0 beta, respectively. All these changes make CdS:Co extremely interesting system for the spintronic applications.