First-principles insights into X2MgS4 (X= Pm, Pr) spinels for energy harvesting and spintronic applications

Herein, ab initio calculations have been performed on X₂MgS₄ (X = Pm, Pr) spinel sulfides in order to explore the physical attributes such as geometric, magnetic, optoelectronic and thermoelectric characteristics through density functional theory with modified Becke–Johnson potential. The value of tolerance factor (τ) is calculated as 0.98 for both spinels which assures structural stability. Spin resolved band structures indicate semiconducting/half-metallic ferromagnetic ordering in Pm₂MgS₄/Pr₂MgS₄, respectively. Pm₂MgS₄ revealed bands gaps of 1.68 (spin up) and 1.84 eV (spin down), which can be observed in the optical characteristics. In optical parameters, static values of real part ε₁ (0) is 5.1 for Pm₂MgS₄ and 43.2 for Pr₂MgS₄. Maximum R(ω) is recorded as 0.32 at 7.8 eV for Pm₂MgS₄ and 0.34 at 7.4 eV for Pr₂MgS₄. Thermoelectric (TE) parameters are computed with the help of BoltzTraP code within 300–800 K temperature range. Peak value of ZT_(e) is calculated as 0.79 for Pm₂MgS₄ at 800 K, close to the desirable ∼1.0 value of ZT. Our results show that Pm₂MgS₄ spinel can be efficiently used in the field of spintronic and Pm₂MgS₄ for energy harvesting applications.