First-principles investigation of half-metallic ferromagnetism and optical properties of magnesium-based Mg(Fe/Mn)2O4 spinels for spintronic and clean energy

We utilized first principles calculations so as to investigate structural stability, optical, electronic, as well as magnetic properties for Mg(Fe/Mn)${}_2$O${}_4$ spinel alloys. We showed that both compounds are ferromagnetic, with optimal lattice parameters of 8.47 Å for MgFe${}_2$O${}_4$ and 10.07 Å for MgMn${}_2$O${}_4$. The electronic properties revealed that both compounds exhibit semiconductor behavior, with direct band gaps of 0.18 eV for MgFe${}_2$O${}_4$ and 2.8 eV for MgMn${}_2$O${}_4$ in the spin-down state, while displaying metallic behavior in the spin-up state. Additionally, the optical analysis indicates high absorption coefficients in the UV region, coupled with high reflectivity at 0 eV, highlighting their favorable optoelectronic characteristics. Furthermore, the magnetic analysis demonstrates that both compounds exhibit ferromagnetic properties, with magnetic moments approximating 5 ${\mu }_B$ for MgFe${}_2$O${}_4$ and 4 ${\mu }_B$ for MgMn${}_2$O${}_4$. Based on these results, these alloys show potential as candidates for spintronic devices.