Antiferromagnetically Spin Polarized Oxygen and Manganese in MnO Layers Investigated by First Principle and Series Expansions Calculations

Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using the FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnO layers. Polarized spin and spin-orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent Mn layers. Magnetic moment considered to lie along (110) axes are computed. 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 integrals between the magnetic atoms Mn–Mn and Mn–O in the same layer and between the adjacent bilayers are given by using the mean field theory. The antiferromagnetic energies of MnO layers are obtained. The High Temperature Series Expansions (HTSEs) of the magnetic susceptibility on MnO antiferromagnetic layers through Heisenberg and XY models is given up to tenth order series in (x=J _Mn–Mn/k _B T). The reduced Néel temperature x _N is obtained by HTSEs of the magnetic susceptibility and by using the Padé approximant method. The critical exponent γ associated with the magnetic susceptibility is deduced.     

Preparation and characterization of highly stable monodisperse argan oil‐in‐water emulsions using microchannel emulsification

Argan oil is well known for its nutraceutical properties. Its specific fatty acid composition and antioxidant content contribute to the stability of the oil and to its dietetic and culinary values. There is an increasing interest to use argan oil in cosmetics, pharmaceutics, and food products. However, the formulation of highly stable emulsions with prolonged shelf life is needed. In this study, argan oil‐in‐water (O/W) emulsions were prepared using microchannel (MC) emulsification process, stabilized by different non‐ionic emulsifiers. The effects of processing temperature on droplet size and size distribution were studied. Physical stability of argan O/W emulsions was also investigated by accelerated stability testing and during storage at room temperature (25 ± 2°C). Highly monodisperse argan O/W emulsions were produced at temperatures up to 70°C. The obtained emulsions were physically stable for several months at room temperature. Furthermore, emulsifier type, concentration, and temperature were the major determinants influencing the droplet size and size distribution. The results indicated that a suitable emulsifier should be selected by experimentation, since the interfacial tension and hydrophilic–lipophilic balance values were not suitable to predict the emulsifying efficiency. Practical applications: MC emulsification produces efficiently monodisperse droplets at wide range of temperatures. The findings of this work may be of great interest for both scientific and industrial purposes since highly stable and monodisperse argan oil‐in‐water emulsions were produced which can be incorporated into food, cosmetic, or pharmaceutical formulations.     

Hydrogen storage in lithium,sodium and magnesium-decorated on tetragonal silicon carbide

Motivated by the widespread application and fascinating properties of various silicon-carbon nanomaterials, we have extensively investigated the properties of tetragonal silicon carbides (t-SiC) monolayer as a novel 2D material for hydrogen storage.Using calculations of the density functional theory comprising van der Waals interactions of type vdW-DF2-C09_x, the structural stability, electronic properties and hydrogen molecules adsorption energies on the surface of pure t-SiC were investigated.The results show that adsorption energies of H₂ molecules in this system are stronger than that of graphene. We also found that the decoration with alkali (Li, Na) and alkaline-earth (Mg) metals atoms increases the stability of hydrogen compared to the pure system. The studied system decorated with 8 elements of Li/Na/Mg is able to adsorb up 24 molecules of hydrogen and reaches a gravimetric capacity of 6.50, 5.54 and 5.48 wt%, respectively. The desorption temperatures found are significantly high compared to other 2D systems.     

Mean field approximation and ab initio calculation of magnetic and optical properties of DyN doped with transition metals (TM: V and Cr)

The structural, optical, and magnetic properties of rare earth nitride \(\hbox {Dy}_{0.95}\hbox {TM}_{0.05}\hbox {N}\) (TM: V and Cr) diluted magnetic semiconductors have been investigated using the Korringa–Kohn–Rostoker method combined with the coherent potential approximation. In this work, the effect of GGA–SIC approximations on the electronic properties was investigated in detail. It is revealed from calculating the density of states (DOS) and optical absorption spectra that the ferromagnetic state is stable when TM introduces magnetic moments in \(\hbox {Dy}_{0.95}\hbox {TM}_{0.05}\hbox {N}\) (TM: V and Cr). Using the mean field approximation (MFA), the Curie temperature is determined by the total energy difference per V and Cr atoms between the disorder local moment (DLM) and ferromagnetic (FM) state within the ambient conditions, which becomes more important by increasing the concentration or by co-doping (V, Cr) DyN systems.     

Kinetic Monte Carlo and density functional study of hydrogen diffusion in magnesium hydride MgH2

In this work, we propose a model to investigate the hydrogen storage ab/desorption kinetic properties for the pure MgH₂ using Kinetic Monte Carlo (KMC) simulations. To do such computations, the activation energies for different elementary processes have been estimated. Moreover, the different thermodynamical quantities of interest are determined by performing the ab-initio calculations. Then, we discuss the hydrogen diffusion in magnesium hydride (such as adsorption, diffusion and desorption). More precisely, we study the effect of each elementary mechanism on the diffusion that we characterize through the density distribution of hydrogen atoms including filling ratios, diffusion time, temperature and pressure. Among others, we show that all elementary mechanisms are needed to reproduce a behavior of ab/desorption which correlates well with the experimental results reported in literature. In particular, at high temperature and pressure, the results of simulations indicate that the studied material involves slow kinetics.     

New results on Magnetic Properties of Tin-Ferrite Nanoparticles

This paper presents new physical properties of nanocrystalline SnFe₂O₄ ferrites, synthesized by co-precipitation method. Magnetization measurement indicates superparamagnetic behavior; the blocking temperature is about 300?K. We performed X-ray diffraction, infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), Energy Dispersive Spectroscopy (EDS), UV-visible measurement, superconducting quantum interference device (SQUID) and zero-field-cooled (ZFC)/field-cooled (FC) measurements. TEM images show the high crystallinity and grain size of ferrite nanocrystals. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is a partially inverse spinel. The obtained UV?Cvis data were used to calculate the energy band gap (3.82?eV) of nanocrystalline SnFe₂O₄. On the other hand the magnetic properties of the samples; saturation magnetization (M _s ) and coercive field (H _c ) were determined using a superconducting quantum interference device (SQUID).     

High temperature magnetic properties of nanocrystalline Sn0∙95Co0∙05O2

Structural and magnetic properties of Sn_0?95Co_0?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 Sn_0?95Co_0?05O₂ nanoparticle shows a well-defined hysteresis loop at 300 K temperature, which reflects its ferromagnetic behaviour. We confirmed the roomtemperature 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 Sn_0?95Co_0?05O₂ is also investigated. To explain the origin of ferromagnetic behaviour, we give information about total and atoms projected density of state functions.     

Cation Distribution and Magnetic Interactions in Zn-Substituted Fe(Cu)Fe2O4 Ferrites

The effect of Zn doping on magnetic properties of Fe₃O₄ and CuFe₂O₄ ferrite spinels has been studied. The general expression of saturation magnetization, the critical temperature and Curie constant (C) are obtained by the mean field theory (MFT). By considering the high-temperature series expansions (HTSE) theory and the mean field approximation for the Néel??s two-sublattice noncollinear model, we obtained the magnetic phase diagrams of Zn _x Fe_1?x Fe₂O₄, and Zn _x Cu_1?x Fe₂O₄. The Bohr magnetron is obtained for two systems. The central critical exponent ?? associated with magnetic susceptibility for two systems is obtained.     

Parallel matrix factorization-based collaborative sparsity and smooth prior for estimating missing values in multidimensional data

Pattern Analysis and Applications - Parallel matrix factorization has recently emerged as a powerful tool for low-rank tensor recovery problems. However, using only the low-rank property is often...