Growth environment dependent phase propagation of ilmenite-hematite (1-x)FeTiO₃-xFe₂O₃ films

We investigated crystal structures, charge ordering, and magnetic properties of ilmenite-hematite (IH) (1-x)FeTiO₃-xFe₂O₃ films grown at various temperatures and oxygen flow rates. The IH solid solution films grown below 650 °C without O₂ have weak magnetic moments due to the Fe²⁺ in the FeTiO₃ phase and Fe³⁺ in the α-Fe₂O₃. The film grown at 650 °C without O₂ exhibits the Neel temperature of ∼60 K and a large magnetic moment due to the Fe²⁺ ions, resulting from an ordered FeTiO₃ phase. Furthermore, the films grown at 650 °C under the O₂ have an α-Fe₂O₃ phase separated from FeTiO₃ due to excessive O₂ during growth. As a result, the film has weak magnetic moments attributed to Fe³⁺ in the α-Fe₂O₃ phase. These observations show that the crystal phase and charge ordering are sensitive to the amount of O₂ and responsible for magnetic properties in the ilmenite-hematite system.