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.