Study of the electronic, magnetic, and thermoelectric aspects of spinel chalcogenides SrCe2Z4 (Z = Te, Se, S) for spintronic and energy applications

Abstract

Spinel chalcogenides are promising candidates for the advancement of spintronic and thermoelectric devices. Therefore, this article presents the structural, electronic, and magnetic characteristics of SrCe₂Z₄ (Z = S, Se, Te) spinels employing WIEN2k in the context of density functional theory. The expansion of the unit cell is witnessed with the incorporation of larger anions and lattice parameters, including 12.01 Å for SrCe₂S₄, 12.52 Å for SrCe₂Se₄, and 13.42 Å for SrCe₂Te₄. The maximum release of energy in the FM states (rather than AFM states) and the negative enthalpy of formation (−2.20 eV, −2.05 eV, and −1.94 eV) confirm their dominant ferromagnetic nature and the thermodynamic stability of the system. The spin-polarized band structure exhibits the ferromagnetic semiconducting nature of SrCe₂S₄ and SrCe₂Te₄, as well as the half-metallic ferromagnetic behavior of SrCe₂Se₄. The analysis of the total density of states also endorses the exact nature predicted during the band structure investigation. The magnetic properties are explored by calculating the direct exchange energy Δ_x(f), indirect exchange energy Δ_x(pf), along with the exchange constants N_oα and N_oβ to analyze the magnetic behavior. The significant hybridization of chalcogenide's 2p states and the f states from the Ce atom located at the Fermi level results in the total magnetic moments. All these compositions reveal that the Curie temperature is near or above room temperature. The thermoelectric characteristics of the spinels are examined utilizing the BoltzTrap code to inspect the parameters including power factors and the figure of merit as a function of temperature. The ZT value of 0.90 for SrCe₂Te₄ indicates its higher thermoelectric efficiency and potential for future thermoelectric devices.