First-Principles Insight on Electronic and Magnetic Properties of SrFeTe-Based Double and Triple Perovskites

This study elucidates the contrasting electronic and magnetic behaviors of SrFeTe-based double and triple perovskites through first-principles calculations. The triple perovskite Sr₃Fe₂TeO₉ exhibits much stronger antiferromagnetic (AFM) coupling (40.295 meV) due to direct Fe-O-Fe superexchange, while the double perovskite Sr₂FeTeO₆ shows weaker interactions mediated by Te-bridged pathways. Both systems adopt AFM ground states, but the triple perovskite demonstrates higher thermodynamic stability and a larger bandgap (2.02 eV versus 0.40 eV). Magnetic anisotropy analysis identifies [0 0 1] as the preferred magnetization axis, with double perovskites requiring higher energy for spin reorientation. Structural differences in Sr coordination and Te-O bonding further influence the charge distribution and localization. These insights highlight the critical role of cation ordering and exchanging pathways of the complex perovskite, offering a foundation for optimizing perovskite-type materials in spintronics and energy applications.