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ARTICLE

Systematic investigation of magneto-electronic, structural, thermoelectric and optical properties of Nd₂MgX₄ (X = S, Se) compounds

M. Fida^a, Nasarullah^a, S. A. Aldaghfag^b, M. Yaseen^a,*, M. Ishfaq^a

a Spin-Optoelectronics and Ferro-Thermoelectric (SOFT) Materials and Devices Laboratory, Department of Physics, University of Agriculture, Faisalabad 38040, Pakistan
b Department of Physics, College of Sciences, Princess Nourah bint Abdulrahman University, P. O. Box 84428, Riyadh 11671, Saudi Arabia

* Corresponding Author:

Chalcogenide Letters 2023, 20(8), 559-562. https://doi.org/10.15251/CL.2023.208.559

Received 18 May 2023; Accepted 03 August 2023;

Abstract

The structural, magnetic, optoelectronic, and thermoelectric (TE) characteristics of Nd₂MgX₄ (X = S, Se) are determined by utilizing the density functional theory (DFT) based full potential linearized augmented plane wave (FP-LAPW) method as employed in WEIN2k code. The exchange and correlation energies along with Coulomb interactions are brought into consideration by employing local density of approximation with Hubbard model (LDA+U). Tolerance (τ) factor and formation enthalpy were utilized to confirm the stability of both spinels. τ values are 0.70 and 0.68, and formation enthalpy values are (ΔH_f) are -3.34 eV and -2.19 eV for Nd₂MgX₄ (X = S, Se), respectively. For Nd₂MgX₄ (X = S, Se) metallic behavior is found in spin up case while considerable bandgaps are found in spin down with half metallic bandgap (E_g) values of 1.82 and 1.26 eV (in spin down), correspondingly. The calculated magnetic moment for Nd₂MgX₄ (X = S, Se) are 12.0008 μ_B and 12.0003 μ_B, respectively. Furthermore, optical features including refractive index n(ω), dielectric constant ε(ω), reflectivity R(ω), optical conductivity σ(ω), absorption coefficient α(ω) and extinction coefficient k(ω) are computed. The maximum calculated real part of dielectric constant ε₁(ω) values for Nd₂MgX₄ (X = S, Se) are 9.2 and 10.8, respectively. For Nd₂MgX₄ (X = S, Se), σ(ω) has maximum value of 7642.9 at 6.6 and 7592.5 (Ω cm) ^-1 at 5.99 eV, respectively. The various temperature dependent thermoelectric (TE) parameters along with figure of merit (ZT) are determined to get full insight into the TE behavior for both compounds by using BoltzTraP code. The computed ZT value for Nd₂MgSe₄ is 0.81 at 800 K while Nd₂MgS₄ has ZT value of 0.80 at 800 K. Results showed that both spinels have potential in spintronics and in cooling industries.

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