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[en] Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume—Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multilayer magnetic order—disorder transition temperature depends strongly on the value of the transverse anisotropy. The multilayer transition temperature decreases when increasing the transverse anisotropy. Furthermore, there exists a critical quantum transverse anisotropy ΔxL beyond which the separate transitions occur in the two magnetic layers. The critical transverse anisotropy ΔxL decreases (increases) on increasing the non-magnetic spacer of thickness M (on increasing the crystal field), and ΔxL undergoes oscillations as a function of the Fermi level. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
[en] The perovskite type oxide SrHfO had a huge scientist interest for the past few years thanks to its properties, which allowed it to be applied in different area, in our case we focused on the photovoltaic field application and it is known that this technology has been based on the use of semiconductors with a specific gap value since its birth, which indicates that the gap value is an important element who influences on the efficiency of panels. The aim of our work is based on reducing the gap value by applying different percentage of doping SrHfOS (x = 0%, 8% and 16%) and the determination of electronic and optical properties of all percentage of S using density functional theory (DFT). As a result we reduced the gap value from 5.60 eV corresponding to 0% of S to 2.09 eV corresponding to 16% of S and the band gap is changed from an indirect band gap equivalent to 0% of S to a direct band gap for 8% and 16% of S.
[en] Based upon the ab initio of spin density functional calculation, the electronic and magnetic properties of Zn1−xMxO (M = Ag or V) and Zn1−x−yAxByO (A = V; B = Ag) are investigated, using the Korringa-Kohn-Rostoker (KKR) method coupled with the coherent potential approximation (CPA). The total and partial densities of state are calculated. The effect of concentration values in Zn1−xVxO and Zn1−x−yVxAgyO are deduced. Moreover, the magnetic disorder local moment (DLM) and the total energy are obtained for different concentration values of doped and co-doped zinc oxide (ZnO).
[en] Crystalline quality and the silanoles defects (Si-OH) present within the structure of natural SiO_2 play an important role in its reactivity. In this work, the relationship between the loss of silanoles and the crystallinity improvement upon heating between 450 °C and 650 °C was shown using X-Ray Diffraction (XRD) and Fourier Transform mid Infrared Spectroscopy in Attenuated Total Reflection (ATR). A shift of the principal band Si-O-Si from 1078 cm"−"1 to 1082 cm"−"1 and the decrease of the intensity of the Si-OH bands at 555cm"−"1and at 950cm"−"1 upon heating between 450 °C and 650 °C were shown. The reduction of the band is correlated to the loss of silanoles. In agreement with FT-IR results, the decrease of the FWHM of the XRD peaks shows that the crystalline quality is improved upon heating. This result leads to a decrease of the reactivity of SiO_2 aggregate under chemical attacks
[en] Highlights: • We have studied the magnetocaloric effect of the metallic antiperovskite compound Mn3GaC. • We used the ab-initio calculations, the Monte Carlo simulations and mean field theory. • A second-order ferromagnetic-paramagnetic phase transition about TC ∼ 249 K. • The magnetic moment and the exchange coupling interactions are calculated. - Abstract: The structural, electronic, magnetic, and magnetocaloric properties of the metallic antiperovskite compound Mn3GaC were investigated using several theoretical methods such as: First principle calculations, Monte Carlo simulations and mean field theory. The metallic antiperovskite compound Mn3GaC exhibits a second-order ferromagnetic-paramagnetic phase transition around TC = 249 K. Using the first principle calculations, the magnetic moment and the exchange coupling interactions values are 1.37 μB and J1 = 35.78meV, J2 = 40.16meV, respectively. The total magnetization, the susceptibility and the specific heat of this compound are calculated. The critical temperature obtained is in good agreement with the experimental results. Obviously, the large MCE with no hysteresis loss is obtained around TC. The maximum values of the magnetic entropy change (ΔSmag), adiabatic temperature change (ΔTad) and the relative cooling power (RCP) are 13.41 J/kg.K, 15.96 K, 748 J/kg respectively, under applied an external magnetic field of h = 5.0 T.