ε-Fe2O3, a metastable phase of iron oxide, is widelyknown as a room-temperature multiferroic material or as asuperhard magnet. Element substitution into ε-Fe2O3 has beenreported in the literature; however, the substituted ions have astrong site preference depending on their ionic radii and valence.In this study, in order to characterize the crystal structure andmagnetic properties of ε-Fe2O3 in the Fe2+/Fe3+ coexisting states, + 3+Li was electrochemically inserted into ε-Fe2O3 to reduce Fe .The discharge and charge of Li+ into/from ε-Fe2O3 revealed thatLi+ insertion was successful. X-ray magnetic circular dichroismresults indicated that the reduced Fe did not exhibit sitepreference. Increasing the Li+ content in ε-Fe2O3 resulted in decreased saturation magnetization and irregular variation of thecoercive field. We present a comprehensive discussion of how magnetic properties are modified with increasing Li+ content usingtransmission electron microscopy images and considering the Li+ diffusion coefficient. The results suggest that inserting Li+ intocrystalline ε-Fe2O3 is a useful tool for characterizing crystal structure, lithiation limit, and magnetic properties in the coexistence of2+ 3+ Fe /Fe .
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