First principles computation of exchange mechanism, radiation shielding, and physical properties of FeCu2SnX4(X=S, Se, Te): Transitions metal based chalcogenides for spintronic and energy storage system applications

Abstract

This study explores the multifunctional properties of Cu-based FeCu₂SnX₄(X = S, Se, Te) through density functional theory (DFT) calculations, focusing on their ferromagnetic stability, optical behavior, and thermoelectric performance. Phonon dispersions and negative formation energy values validated the stability of the ferromagnetic phase of all the investigated spinels. Band structure analysis confirmed semiconducting characteristics for both spin channels, while exchange splitting energies obtained from the density of states (DOS) were used to calculate exchange constants (N₀α and N_0β). The strong p-d hybridization, reflected in higher N_0β = −0.14, −0.18, and −0.16 and N_0α = 0.11, 0.29, and 0.35, indicated that the exchange field dominates the crystal field, driving ferromagnetism. Furthermore, p-d hybridization adjusted magnetic moments at Cu and Fe sites, showcasing tunable magnetic properties. Optical analysis in the 0–6 eV photon energy range revealed low light dispersion and refractive indices of 1–2 eV within the visible spectrum, suggesting potential for optoelectronic applications. Thermoelectric studies at 500 K demonstrated positive Seebeck coefficients for FeCu₂SnS₄ and FeCu₂SnSe₄, while FeCu₂SnTe₄ showed negative coefficients at room temperature. Power factors increased with temperature from X = S to Te, highlighting their potential for thermoelectric power generation. Furthermore, the radiation shielding assessment emphasized that FeCu₂SnTe₄ provides an HVL of a minimum of 0.18 cm at 0.015 MeV, which clearly explains gamma-ray absorption more than other samples. This information places FeCu₂SnX₄ spinel structures as potential candidates for applications that require combined magnetic, optical, radiation shielding, and energy functionalities. These findings position FeCu₂SnX₄ spinels as promising materials for integrated magnetic, optical, radiation shielding, and energy applications.