Faculty of Pure and Applied Science

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Browsing Faculty of Pure and Applied Science by Author "A. S. Ahmed"

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    (Acta Physica Polonica A, 2024-04-03) A. A. Yahaya; W. A. Yahya; A. S. Ahmed; A. A. Sholagberu
    Device applications in magnetic media, spintronics, oxygen membranes, sensors, etc., are some of the uses of ferrite materials. In this work, we have studied the structural, electronic, magnetic, mechanical, and thermoelectric properties of Cs-based double perovskites Cs 2 AX 6 (A = Ge, Mn; X = Cl, I), using Quantum Espresso with generalized gradient approximation Perdew–Burke–Ernzerhof and Perdew– Burke–Ernzerhof in solids exchange–correlation functionals. The band structure results show that Cs 2 GeCl 6 and Cs 2 MnCl 6 are semiconductors with direct band gaps. However, there are bands crossing observed for Cs 2 GeI 6 from the conduction band minimum to the valence band maximum, indicating the metallic nature of the material. Moreover, Cs 2 MnI 6 has magnetic properties; it exhibits a metal- lic nature in the spin-up state and a semiconductor nature in the spin-down state, suggesting that it can be used in spintronics applications. The calculated total magnetic moment of Cs 2 MnCl 6 is 3.0µ B (for both Perdew–Burke–Ernzerhof and Perdew–Burke–Ernzerhof in solids), while for Cs 2 MnI 6 , the calculated total magnetic moments are 3.02µ B and 3.06µ B , for Perdew–Burke–Ernzerhof and Perdew– Burke–Ernzerhof in solids exchange–correlation functionals, respectively. The results of the mechanical properties calculations show that Cs-based double perovskites Cs 2 AX 6 (A = Ge, Mn; X = Cl, I) are mechanically stable. Cauchy’s pressure and Poisson’s, Frantsevich’s, and Pugh’s ratios of the studied materials confirm that Cs 2 MnCl 6 is brittle, while the remaining studied double perovskite materials are ductile. Electrical conductivity, thermal conductivity, Seebeck coefficients, power factor, and figure of merit are the thermoelectric parameters analyzed in this study. Seebeck coefficients, electrical con- ductivity, and power factor increase with the rise in temperature, and Cs 2 MnX 6 (X = Cl, I) double perovskite materials have higher values of electrical conductivity than Cs 2 GeX 6 (X = Cl, I). All the studied materials have positive type conductivity due to their positive Seebeck coefficient values.