Half-metallic Ferromagnetism in Non-magnetic Double Perovskite Oxides Sr2MSbO6 (M=Al, Ga) Doped with C and N.

Double perovskite oxides have gained tremendous attention in material science and device technology due to their facile synthesis and exceptional physical properties. In this paper, we elucidate the origin of magnetization in non magnetic double perovskite oxides Sr2MSbO6 (M=Al, Ga) induced by non-magnetic 2p-impurities (C and N) substituted. The calculations were done within the full potential linearized augmented plane wave method (FP-LAPW) in the framework of the density functional theory (DFT). The exchange-correlation potential is evaluated using the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) and the modified Becke and Johnson (mBJ-GGA). Regarding structural properties of undoped double perovskites Sr2MSbO6 (M=Al, Ga), we found that the lattice constants and oxygen positions are in rational accord with the experimental results. Furthermore, both of the examined compounds are brittle in nature with isotropic character. For Sr2AlSbO6 we have got the values of energy gap equal to 1.9 eV and 3.7 eV within the GGA and the mBJ-GGA, respectively. However for Sr2GaSbO6 the values of energy gap obtained in GGA and mBJ-GGA are equal to 0.8 eV and 2.9 eV, respectively. Finally, spin-polarized calculations reveal that the doping C and N can lead to drastic changes in the magneto-electronic properties of the semiconducting Sr2MSbO6 matrix with the integer magnetic moment of 6.00 µB and exhibit half-metallic properties. The origin of ferromagnetism can be attributed to the spin–split impurity bands inside the energy gap of the semiconducting Sr2MSbO6 matrix. These results may help experimentalists in synthesizing new double perovskites for spintronic applications.

New Insights into Cd2+/Fe3+ Co-Doped BiOBr for Enhancing the Photocatalysis Efficiency of Dye Decomposition under Visible-Light

Uniform flowerlike microspheres Cd2+/Fe3+ co-doped BiOBr were prepared with the aid of the microwave hydrothermal process. The results indicate that the degradation performance of Bi1−xCdxOBr and Bi1−xFexOBr are 1.31 and 2.05 times that of BiOBr for RhB, respectively. Moreover, the novel Cd2+/Fe3+ co-doped BiOBr photocatalysts with ~0.42 eV impurity bands presented remarkably enhanced photocatalytic activities with being 3.10 times that of pure BiOBr, by achieving e−/h+ efficient separation and narrowed bandgap with the ions synergistic effect of Cd2+ and Fe3+. Based on DFT insights, the photodegradation mechanism was systematically studied that the conversion of multivalent Fe3+ ions promoted the production of •O2−, and Cd2+ ions worked as electron transfer mediators, which elucidated that the •O2− and h+VB mainly participated in the catalytic reaction. The experimental and theoretical results show that the synergistic effects of multi-ion doping have great potential in the field of photocatalysis.

Low Temperature Conductivity inn-Type Noncompensated Silicon below Insulator-Metal Transition

We investigate the transport properties ofn-type noncompensated silicon below the insulator-metal transition by measuring the electrical and magnetoresistances as a function of temperatureTfor the interval 2–300 K. Experimental data are analyzed taking into account possible simple activation and hopping mechanisms of the conductivity in the presence of two impurity bands, the upper and lower Hubbard bands (UHB and LHB, resp.). We demonstrate that the charge transport develops with decreasing temperature from the band edge activation (110–300 K) to the simple activation with much less energy associated with the activation motion in the UHB (28–90 K). Then, the Mott-type variable range hopping (VRH) with spin dependent hops occurs (5–20 K). Finally, the VRH in the presence of the hard gap (HG) between LHB and UHB (2–4 K) takes place. We propose the empiric expression for the lowTdensity of states which involves both the UHB and LHB and takes into account the crossover from the HG regime to the Mott-type VRH with increasing temperature. This allows us to fit the lowTexperimental data with high accuracy.

The Electronic Structure and Optical Properties of Co,C Co-Doped AlN Nanosheet

The electronic structure, band structure and optical properties of Co,C co-doped AlN are investigated by first-principles calculations. The calculated results show that some impurity bands emerge near the Fermi level, and the degree of hybridization becomes stronger for Co 3d states and Al 3s states. Which indicates that the electron transition become more active from valence band to conduction band and the electrical conductivity is enhanced. Compared with intrinsic AlN, the optical properties of co-doped AlN improves a lot. There emerge some new peaks in the low energy region and the absorption coefficient, reflectivity and refractive index has large improvement in visible and infrared range.

Electronic and magnetic properties regulation of finite to infinite half sandwich organo-transition-metal-complexes functionalized graphene

Total band gaps (Δt) and band gaps of free “graphene”, ignoring impurity bands of TMnOLs (Δg).