• E K Hlil

Articles written in Bulletin of Materials Science

• Discrepancy of room temperature ferromagnetism in Mo-doped In2O3

Molybdenum-doped indium oxide nanopowders were synthesized via mechanical alloying with subsequent annealing at a relatively low temperature of 600 °C. Themorphologies and crystal structures of the synthesized nanopowders were examined by using scanning electron microscopy (SEM) and X-ray diffraction patterns. X-ray diffraction pattern of the milled mixture shows the presence of both In2O3 phase and Mo element. The presence of broad peaks in the pattern confirms that the synthesized powders are nanosized. The X-ray diffraction of annealed samples at 600 °C shows the absence of Mo peaks revealing that the Mo was incorporated into the crystal lattices of In2O3. Interestingly, it was observed that the diffraction peaks were still broad in the annealed samples indicating the single phase at the nanoscale. From the XRD pattern, the calculated crystallite sizes were in the range of 12–18 nm. Magnetic properties of the synthesized Mo-doped In2O3 nanopowders were examined and it was found that the obtained nanopowders possess diamagnetic properties.

• Structural, magnetic and electronic transport studies of RAgSn2 compounds (R = Y, Tb, Dy, Ho and Er) with Cu3Au-type

RAgSn2 compounds, where R = Y, Tb, Dy, Ho and Er, were synthesized by arc-melting and subsequent annealing at 870 K. The formation of cubic phases with Cu3Au-type structure (space group 𝑃𝑚$\bar{3}$𝑚) was studied. Magnetic property measurements showed that in paramagnetic state, the compounds with magnetic rareearth atoms are Curie–Weiss paramagnets and order antiferromagnetically at low temperatures. YAgSn2 is a Pauli paramagnet in 100–300 K temperature range. The electrical properties of RAgSn2 compounds were investigated by means of electrical resistivity and Seebeck coefficient measurements in 4.2–300 K temperature range. All investigated compounds exhibit metallic type of conductivity. Electronic structure calculations based on full potential linearized augmented plane wave (FLAPW)method is also carried out to probe themagnetic and electronic structures of RAgSn2 compounds. Comparisons between experimental data and calculations are discussed.

• High temperature magnetic properties of nanocrystalline Sn0.95Co0.05O2

Structural and magnetic properties of Sn0.95Co0.05O2 nanocrystalline and diluted magnetic semiconductors have been investigated. This sample has been synthesized by co-precipitation route. Study of magnetization hysteresis loop measurements infer that the sample of Sn0.95Co0.05O2 nanoparticle shows a well-defined hysteresis loop at 300 K temperature, which reflects its ferromagnetic behaviour. We confirmed the room-temperature intrinsic ferromagnetic (FM) semiconductors by ab initio calculation, using the theory of the functional of density (DFT) by employing the method of Korringa–Kohn–Rostoker (KKR) as well as coherent potential approximation (CPA, explain the disorder effect) to systems. The ferromagnetic state energy was calculated and compared with the local-moment-disordered (LMD) state energy for local density approximation (LDA) and LDA–SIC approximation. Mechanism of hybridization and interaction between magnetic ions in Sn0.95Co0.05O2 is also investigated. To explain the origin of ferromagnetic behaviour, we give information about total and atoms projected density of state functions.

• Study of Cu-doping effects on magnetic properties of Fe-doped ZnO by first principle calculations

Using ab initio calculations on Zn0.975–𝑥Fe0.025Cu𝑥O (𝑥 = 0, 0.01, 0.02, 0.05), we study the variations of magnetic moments vs Cu concentration. The electronic structure is calculated by using the Korringa–Kohn–Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that the total magnetic moment and magnetic moment of Fe increase on increasing Cu content. From the density of state (DOS) analysis, we show that Cu-induced impurity bands can assure, by two mechanisms, the enhancement of Fe magnetic moment in Zn0.975–𝑥Fe0.025Cu𝑥O.

• First principle calculations for improving desorption temperature in Mg16H32 doped with Ca, Sr and Ba elements

Using ab initio calculations, we predict the improvement of the desorption temperature and the hydrogen storage properties of doped Mg-based hydrides such as,Mg15AMH32 (AM = Ca, Sr and Ba) as a super cell 2 × 2 × 2 of MgH2. In particular, the electronic structure has been obtained numerically using the all-electron full-potential local-orbital minimum-basis scheme FPLO9.00-34. Then, we discuss the formation energy calculations in terms of the material stabilities and the hydrogen storage thermodynamic properties improvements. Among others, we find that the stability and the temperature of desorption decrease without reducing significantly the high storage capacity of hydrogen. Moreover, it has been observed that such a doping procedure does not affect the electronic behavior as seen in MgH2, including the insulator state in contrast with the transition metal hydrides, which modify the electronic structure of pure MgH2.

• Structural, electronic and magnetic properties of MnB2

The self-consistent ab-initio calculations, based on density functional theory approach and using the full potential linear augmented plane wave method, are performed to investigate both electronic and magnetic properties of the MnB2 compounds. Polarized spin and spin–orbit coupling are included in calculations within the framework of the ferromagnetic state between two adjacent Mn atoms. Magnetic moment considered to lie along the (001) axes are computed. The antiferromagnetic and ferromagnetic energies of MnB2 systems are obtained. Obtained data from ab-initio calculations are used as input for the high-temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The exchange interactions between the magnetic atoms Mn–Mn in MnB2 are established by using the mean field theory. The HTSEs of the magnetic susceptibility with the magnetic moments in MnB2 (𝑚Mn) through Ising model is given. The critical temperature 𝑇C (K) is obtained by HTSEs applied to the magnetic susceptibility series combined with the Padé approximant method. The critical exponent 𝛾 associated with the magnetic susceptibility is deduced as well.

• Explanation of ferromagnetism origin in N-doped ZnO by first-principle calculations

By $ab-initio$ calculations, the possible source of ferromagnetism in N-doped ZnO compound was systematically studied. The electronic structure and magnetic properties of N-doped ZnO with/without ZnO host and N defects were investigated using the Korringa–Kohn–Rostoker method combined with coherent potential approximation. It was shown that Zn vacancy and the presence of N defects (substitutional, interstitial or combination of both) induce the ferromagnetism in N-doped ZnO. From density of state analysis, it was shown that p–p interaction between 2p-elements (N,O) is the mechanism of ferromagnetic coupling in N-doped ZnO.

• # Bulletin of Materials Science

Volume 43, 2020
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