Stabilisation of Fe 2 O 3 -rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO 3 Films

Abstract

Researchers have demonstrated that BiFeO 3 exhibits ferroelectric hysteresis but none have shown a strong ferromagnetic response in either bulk or thin film without significant structural or compositional modification. When remanent magnetisations are observed in BiFeO 3 based thin films, iron oxide second phases are often detected. Using aberration-corrected scanning transmission electron microscopy, atomic resolution electron energy loss spectrum-mapping and quantitative energy dispersive X-ray spectroscopy analysis, we reveal the existence of a new Fe 2 O 3 -rich perovskite nanophase, with an approximate formula (Fe 0.6 Bi 0.25 Nd 0.15) 3+ Fe 3+ O 3, formed within epitaxial Ti and Nd doped BiFeO 3 perovskite films grown by pulsed laser deposition. The incorporation of Nd and Bi ions on the A-site and coherent growth with the matrix stabilise the Fe 2 O 3 -rich perovskite phase and preliminary density functional theory calculations suggest that it should have a ferrimagnetic response. Perovskite-structured Fe 2 O 3 has been reported previously but never conclusively proven when fabricated at high-pressure high-temperature. This work suggests the incorporation of large A-site species may help stabilise perovskite-structured Fe 2 O 3. This finding is therefore significant not only to the thin film but also to the high-pressure community.