H. Zaari

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.

Optoelectronic response of spinels CdX2O4 with X = (Al, Ga, In) through the modified Becke–Johnson functional

Structural, electronic, and optical properties of CdAl2O4, CdGa2O4, and CdIn2O4 are investigated using the first principles technique based on the new potential approximation known as the Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ). We discuss the improvements in the band gap determination using TB-mBJ compared to the standard generalized gradient approximation in density functional theory. The calculated equilibrium lattice parameters are in reasonable agreement with the experimental results. Electronic properties have been studied through the calculation of band structure and density of states. Based on our electronic structure obtained using the mBJ method, we have calculated various optical properties, including the complex dielectric function e(ω), complex index of refraction n(ω), reflectivity coefficient R(ω), absorption coefficient α(ω), and the electron energy-loss function L(ω) as functions of the photon energy. We chose these three representative oxides spinel du...

Understanding ferromagnetism and optical absorption in 3d transition metal-doped cubic ZrO2 with the modified Becke-Johnson exchange-correlation functional

The electronic structure, magnetic, and optical properties in cubic crystalline phase of Zr1−xTMxO2 (TM = V, Mn, Fe, and Co) at x = 6.25% are studied using density functional theory with the Generalized Gradient Approximation and the modified Becke-Johnson of the exchange-correlation energy and potential. In our calculations, the zirconia is a p-type semiconductor and has a large band gap. We evaluated the possibility of long-range magnetic order for transition metal ions substituting Zr. Our results show that ferromagnetism is the ground state in V, Mn, and Fe-doped ZrO2 and have a high value of energy in Mn-doped ZrO2. However, in Co-doped ZrO2, antiferromagnetic ordering is more stable than the ferromagnetic one. The exchange interaction mechanism has been discussed to explain the responsible of this stability. Moreover, it has been found that the V, Mn, and Fe transition metals provide half-metallic properties considered to be the leading cause, responsible for ferromagnetism. Furthermore, the optical...

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.