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Tissemsilt, Algeria

Dahmane F.,Center University Of Tissemsilt | Dahmane F.,University Djilali Liabes | Mogulkoc Y.,Ankara University | Doumi B.,University Djilali Liabes | And 6 more authors.
Journal of Magnetism and Magnetic Materials

Using the first-principles density functional calculations, the structural, electronic and magnetic properties of the Fe2XAl (X=Cr, Mn, Ni) compounds in both the Hg2CuTi and Cu2MnAl-type structures were studied by the full-potential linearized augmented plane waves (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA) where the results show that the Cu2MnAl-type structure is energetically more stable than the Hg2CuTi-type structure for the Fe2CrAl and Fe2MnAl compounds at the equilibrium volume. The full Heusler compounds Fe2XAl (X=Cr, Mn) are half-metallic in the Cu2MnAl-type structure. Fe2NiAl has a metallic character in both CuHg2Ti and AlCu2Mn-type structures. The total magnetic moments of the Fe2CrAl and Fe2MnAl compounds are 1.0 and 2.0 μB, respectively, which are in agreement with the Slater-Pauling rule Mtot=Ztot- 24. © 2016 Elsevier B.V. All rights reserved. Source

Elahmar M.H.,University Djilali Liabes | Rached H.,University Djilali Liabes | Rached H.,University of Hassiba Ben Bouali Chlef | Rached D.,University Djilali Liabes | And 4 more authors.
Materials Science- Poland

We investigated the structural stability as well as the mechanical, electronic and magnetic properties of the Full-Heusler alloy CoNiMnSi using the full-potential linearized augmented plane wave (FP-LAPW) method. Two generalized gradient approximations (GGA and GGA + U) were used to treat the exchange-correlation energy functional. The ground state properties of CoNiMnSi including the lattice parameter and bulk modulus were calculated. The elastic constants (Cij) and their related elastic moduli as well as the thermodynamic properties for CoNiMnSi have been calculated for the first time. The existence of half-metallic ferromagnetism (HM-FM) in this material is apparent from its band structure. Our results classify CoNiMnSi as a new HM-FM material with high spin polarization suitable for spintronic applications. © 2016 M.H. Elahmar et al., published by De Gruyter Open. Source

Doumi B.,Saida University | Doumi B.,University Djilali Liabes | Mokaddem A.,University of Science and Technology Houari Boumediene | Temimi L.,University of Science and Technology of Oran | And 7 more authors.
European Physical Journal B

We have investigated the electronic structure and half-metallic ferromagnetism of Sr1−xCrxZ (Z = S, Se, and Te) in rock-salt structure at concentrations x (x = 0.125, 0.25, 0.5, 0.75 and 0.875) of Cr, using first-principles calculations of density functional theory. The electronic and magnetic properties show that Sr1−xCrxZ (Z = S and Se) at x = 0.125, 0.25, 0.5, 0.75 and Sr1−xCrxTe at all concentrations are half-metallic ferromagnets (HMF) with spin polarization of 100% and total magnetic moments of 4μB per Cr atom, whereas the HMF character destroyed for Sr1−xCrxZ (Z = S and Se) at x = 0.875. The integrals Bohr magneton of total magnetic moments confirm the half-metallic ferromagnetic behavior of Sr1−xCrxZ. We have found that the ferromagnetic state is stable by the 3d-eg (Cr) partially filled states associated with the double-exchange mechanism. Therefore, the Sr1−xCrxS, Sr1−xCrxSe, and Sr1−xCrxTe at low concentration are predicted to be new potential candidates for spintronic applications. © 2015, EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source

Zegaou B.,University Djilali Liabes | Benkhettou N.,University Djilali Liabes | Rached D.,University Djilali Liabes | Reshak A.H.,University of West Bohemia | And 3 more authors.
Computational Materials Science

The electronic and magnetic properties of the ferromagnetic laves-phase GdX2 (X = Fe, Co and Ni) intermetallic compounds were calculated by using an all-electron full-potential linear muffin-tin orbital method (FP-LMTO) within GGA and GGA + U. The so-called GGA + U method is applied to properly treat the Gd-4f electron in the electronic structure calculation. The GGA improves the agreement between experiments and calculations for the lattice constants; however the GGA + U overestimates them, but gives a better representation of the band structure, density of states and magnetic moments compared to GGA alone. The reduction of the Co and Ni magnetic moments in the GdCo2 and GdNi2 compared to that in pure metals is due to the different localization strength of the transition metal and the same reason in the enormous reduction of the Curie temperatures. © 2014 Elsevier B.V. All rights reserved. Source

Bidaoui M.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources | Bidaoui M.,Blida University | Bidaoui M.,Center University Of Tissemsilt | Especel C.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources | And 5 more authors.
Journal of Molecular Catalysis A: Chemical

Pt/SBA-15 catalysts, modified by zinc addition (at different Zn/Pt atomic ratios) via the co-impregnation method, were tested for the liquid phase hydrogenation of citral. The influence of the Zn insertion on the Pt monometallic catalyst properties was evaluated by different physico-chemical techniques, including X-ray diffraction, N2-physisorption, transmission electron microscopy, hydrogen chemisorption, and cyclohexane dehydrogenation as model reaction for platinum accessibility and zinc covering evaluation. On the catalysts, the hexagonal periodic structure of SBA-15 framework was maintained indicating that neither Pt and Zn impregnations, nor thermal treatments affect the organized structure of the support. A decrease of the platinum metallic accessibility was observed with the increase in the Zn concentration in the materials, which was explained, on the basis of the TEM analysis, by a poisoning of the platinum accessible sites by zinc species. For the citral hydrogenation, Pt/SBA-15 monometallic catalyst is very active, with 100% conversion obtained after 30 min reaction time, but very poorly selective in unsaturated alcohols. Zinc addition led to an inhibition of the hydrogenating activity, in agreement with the decrease of the active surface, but contributed to an increase in the selectivity to unsaturated alcohols. Selectivity in unsaturated alcohol was observed to reach a maximum of 75%, for a Zn content equal to 0.3 wt.%, that is a very interesting value if compared to performances obtained with other more classical dopant including titania and germanium. © 2015 Published by Elsevier B.V. Source

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