Mustapha Abdellaoui

M-type strontium hexaferrite SrFe[ ]Ni[ ]Al₂O[ ] ([ ], 0.1, 0.2 and 0.3) magnetic powders were prepared by sol–gel auto-combustion method. Their structural, morphological, and magnetic properties were investigated. The prepared powders were calcined at 1200^∘C for 3[ ]h X-ray powder diffraction. The results confirmed that the samples were single-phase, with P63/mmc space group. The average crystallite size was found in the range of 43.94–39.80[ ]nm. The Scanning Electron Microscopy shows that the grain size ranges from 0.33[ ][ ]m to 0.26[ ][ ]m. The magnetic properties were studied by analyzing the hysteresis cycles ([ ]–[ ]. The substitution of Fe by Ni led to a reduction in both coercive field and saturation magnetization. These changes in magnetic properties are correlated with the structural alterations induced by substituting iron ions with nickel ions. The Law of Approach to Saturation (LAS) was used to extract key magnetic parameters, notably the effective anisotropy constant ([ ], giving information about the magnetic behavior of our samples.

Herein, the biaxial strain effect is investigated on the structural, electronic, and optical properties of 1T and 1H phases of Janus CaFBr monolayer in the framework of density functional theory. It is found that both phases of the Janus CaFBr monolayer are direct semiconductors at equilibrium, with bandgaps of 3.90 and 3.55 eV for 1T and 1H phases, respectively. The thermodynamic stability is examined via cohesive energy and phonon dispersion. The bandgap decreases linearly and is nearly parabolic for 1T and 1H phases, respectively, when switching from the tensile to compressive strain with a drastic shift from direct to indirect bandgap at −10% of compressive strains. The calculated dielectric function and optical properties such as reflectivity, refractive index, extinction, and absorption coefficients enhance under biaxial with an improvement of the absorption coefficient especially in the visible and ultraviolet (UV) regions for 1H and 1T phases, respectively, which is in line with the dielectric constant. The results suggest that the Janus CaFBr monolayer might be a potential candidate for optoelectronic applications in visible/UV detection and absorption.

MnFe₂O₄ ferrite nanoparticle was synthesized via the sol–gel method, and structural, morphology and magnetic characteristics were investigated. X-ray diffraction analysis showed that the synthesized sample was in a single phase with a spinel-ferrite-like structure (space group Fd-3m). The scanning electron microscopy displayed homogenous spherical grains with an agglomeration of the particles. The chemical composition determined by energy-dispersive spectroscopy shows the absence of any impurities. To understand the role of magnetic interaction in MnFe₂O₄ spinel ferrites, the structural and magnetic properties of MnFe₂O₄ have been explored theoretically. Based on the first-principles methods via density functional theory and Monte Carlo simulations, the magnetic hysteresis cycle has been plotted. Using the generalized gradient and GGA-PBE approximation in the full-potential linearized augmented plane wave (FP-LAPW) method, the exchange coupling interactions between magnetic elements and local magnetic moment were evaluated. Furthermore, the theoretical magnetic properties of MnFe₂O₄ were found to match the experimental ones. They both revealed that MnFe₂O₄ is a soft ferromagnetic material. The theoretical curve of magnetization versus temperature indicates that the transition occurred at T_c = 580.0 K. This was also in good agreement with the experimental Curie temperature.

Arsenene, a single-layer arsenic nanosheet with a honeycomb structure, has recently attracted increasing attention due to its numerous exceptional properties. In this study, density functional theory (DFT) calculations were employed to investigate and compare the interactions of Li, Na and Mg ions with the Arsenene monolayer for the purpose of using it as an anode in lithium, sodium, and magnesium ion rechargeable batteries. The results indicated that the Li, Na and Mg adatoms preferentially adsorbed on the valley sites, with negative adsorption energies of −2.55, −1.91 and −1.10 eV, respectively. This strong binding between the alkali metals and the Arsenene monolayer is an important factor for battery applications. Also, it was found that Arsenene exhibited high theoretical specific capacities of up to 1430 mA h g⁻¹ for Li and Mg and 1073.18 mA h g⁻¹ for Na, which are extremely higher values than those of commercially used graphite anodes (372 mA h g⁻¹) in Li-ion batteries. Furthermore, the diffusion barrier energies of the Li, Na and Mg ions were calculated using the nudged elastic band method. The activation energy barriers of these ions showed isotropic behavior for the different pathways (X, Y, and diagonal directions), where the obtained values were 0.16, 0.05 and 0.016 eV for Li, Na, and Mg ions, respectively. Our findings indicate that the high capacity, low open circuit voltage, and ultrahigh barrier diffusion make Arsenene a good candidate for application as an anode material for rechargeable batteries.