A.G. El Hachimi

First-principles prediction of the magnetism of 4f rare-earth-metal-doped wurtzite zinc oxide

Abstract Electronic structure and magnetic properties of wurtzite ZnO semiconductor doped with rare earth (RE=La, Ce, Pr, Pm, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) atoms were studied using spin-polarized density functional theory based on the full-potential linear augmented plane wave (FP-LAPW) method as implemented in the Wien2k code. In this approach the generalized gradient approximation (GGA) was used for the exchange-correlation (XC) potential. Our results showed that the substitution of RE ions in ZnO induced spins polarized localized states in the band gap. Moreover, the studied DMSs compounds retained half metallicity at dopant concentration x =0.625% for most of the studied elements, with 100% spin polarization at the Fermi level ( E F ). The total magnetic moments of these compounds existed due to RE 4f states present at E F , while small induced magnetic moments existed on other non-magnetic atoms as well. Finally, the energy difference between far and near configurations was investigated. It was found that the room temperature ferromagnetism was possible for RE-doped ZnO at near configuration. Since the RE-RE separation was long enough (far configuration) for magnetic coupling, the system became paramagnetic or antiferromagnetic ground state.

Electronic structure, optical and magnetic properties of Zn 1−x M x Te (M = Ti, Cr and Mn) Ab initio calculations

Optical and electronic properties of zinc blende ZnTe bulk and doped with transition metals (Ti, Cr and Mn) have been calculated using a Full Potential Augmented Plane Wave (FP-LAPW) method within the density functional theory. The exchange-correlation potential was treated with the Generalized Gradient Approximation (GGA) to calculate the total energy. For the electronic and optical properties calculations, the exchange and correlation effects were treated by the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential to prevent the inconvenience of the underestimation of the energy gaps in GGA. The obtained results are compared to available experimental data and to other theoretical calculations.

The investigations of electronic structure, optical and magnetic properties of MgB 2 nanosheets

First principles calculations were performed to study the electronic structures of Magnesium diboride (MgB2) bulk and nanosheet with different layer and thickness in order to understand the influence of layer number and thickness on electronic and optical properties for this compound, using the Full Potential Linearized Augmented Plane Waves (FP-LAPW) method with the Generalized Gradient Approximation (GGA) implemented in Wien2k code. It is shown that the MgB2 is superconductor with Tc=39K, however MgB2 sheet become a nonmagnetic semiconductor and good transparent in the visible range, the absorption coefficient decrease and the superconductor properties appears again with increasing number of layers.