Observations of charge-ordered and magnetic domains in LuFe ₂O ₄ using transmission electron microscopy

Both charge-ordered and magnetic domains produced in LuFe ₂O ₄, which have attracted significant attention due to the interplay of electronic and magnetic degrees of freedom, have been studied using transmission electron microscopy techniques. Dark-field images, obtained using a weak satellite reflection, revealed the nanometer-scale charge-ordered domains, which were observed over a wide temperature range below T _CO (critical temperature of charge ordering; ∼310 K). Electron holography demonstrated an aspect of the long-range magnetic order wherein the magnetic flux lines were completely parallel to the c axis of LuFe ₂O ₄, in a specimen cooled to 17 K under an applied magnetic field. In contrast, there was no appreciable magnetic signal observed in a specimen cooled in a negligible magnetic field. These observations provide useful information for further understanding of the complex magnetic phase transitions in this compound.