We report the structural characterization and transport properties of highly-ordered epitaxial γ-Fe2O3 thin films grown by a pure ozone-assisted molecular beam epitaxy method. X ray diffraction (XRD) measurements at a synchrotron facility indicated that the composition of films was close to that of γ-Fe2O3 with Fe vacancy only occurring at octahedral sites of a spinel. We revealed that the crystal symmetry was reduced from a cubic, giving rise to extra superlattice reflections along the c* axis and this showed good agreement with a tetragonal structure with c ≲ 3a. We succeeded in determining the position of vacancy sites as well as the unit cell by comparing the XRD results with calculated reflection patterns for plausible vacancy ordered models. The temperature dependent resistivity of the vacancy ordered γ-Fe2O3 was several orders higher than that of Fe3O4.
- Ozone beam
- Vacancy ordering