Probing the local atomic structure and magnetism in Iron and manganese co-doped indium oxide Nanocubes using XAS and DFT

Abstract

We examine the impact of iron and manganese co-doping on the local atomic environment in hydrothermally synthesized In₂O₃ using synchrotron X-ray absorption spectroscopy analysis, correlating the findings with the observed magnetic properties. The results revealed that manganese is mainly present in the +3-valence state with a dilute contribution from the +4 state. These oxidation states indicate the formation of oxygen vacancies resulting from charge imbalance. The effective co-substitution of iron and manganese atoms in the In₂O₃ was established, accompanied by specific changes in bond lengths. Additionally, the bond length of MnO slightly increased for In_1.94Fe_0.02Mn_0.04O₃, and subsequently, decreased for the higher Mn-doped samples. Density functional theory calculations revealed that the FeO bond length decreases from 2.194 to 2.141 Å upon the introduction of oxygen vacancies, indicating enhanced FeO interactions. Conversely, the MnO bond increased from 2.140 to 2.210 Å, reflecting the weakened local bonding environment and reduced lattice integration of Mn atoms. Magnetic investigations revealed a room-temperature ferromagnetism in In_1.94Fe_0.02Mn_0.04O₃, characterized by an enhanced coercivity and saturation magnetization. Density functional theory calculations show that oxygen vacancy formation stabilizes the high magnetic moments 3.85 μ_B for Fe and 4.23 μ_B for Mn, driven by FeO and MnO hybridization and increased d-electron localization around the transition metal centers. These findings offer new insights into the local micro-environment and magnetic characteristics of iron and manganese-codoped indium oxide.