Microstructure and physical properties of ε-Fe₂O₃ thin films fabricated by pulsed laser deposition

ε-Fe₂O₃ has attracted intense interest in the field of magnetoelectric materials due to its promising physical properties. The epitaxial growth of ε-Fe₂O₃ thin films is challenging since it is a metastable phase of iron oxide. In this study, ε-Fe₂O₃ (001) thin films are epitaxially grown on SrTiO₃ (111) substrates by pulsed laser deposition (PLD). The crystal structure, valence state, and microstructure of the ε-Fe₂O₃ thin films are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is revealed that the oxygen pressure, deposition and annealing temperatures, and laser beam energy affect significantly the epitaxial growth of ε-Fe₂O₃ thin films. The orientation relationship between films and substrates is ε-Fe₂O₃ (001)[010] // SrTiO₃ (111)[1¯10]. The magnetic hysteresis loops tested by a superconducting quantum interference device and UV-Vis reflection spectra suggest that the ε-Fe₂O₃ thin film with thickness of ∼ 20 nm has a strong magnetic anisotropy, a coercivity of 600 Oe, and an indirect band gap of 3.26 eV.