Ferroelectric and Magnetic Properties in Room‐Temperature Multiferroic GaxFe2−xO3 Epitaxial Thin Films

GaFeO3‐type iron oxide is a promising room‐temperature multiferroic material due to its large magnetization. To expand its usability, controlling the ferroelectric and magnetic properties is crucial. In this study, high‐quality GaxFe2–xO3 (x = 0–1) epitaxial films are fabricated and their properties are systematically investigated. All films exhibit room‐temperature out‐of‐plane ferroelectricity, showing that the coercive electric field (Ec) decreases monotonically with x. Additionally, the films show in‐plane ferrimagnetism with a Curie temperature (TC) >350 K at x = 0–0.6. The coercive magnetic field (Hc) decreases with x at x ≤ 0.6, but shows a constant value at x > 0.6, whereas the saturated magnetization (Ms) increases with x at x ≤ 0.6, but decreases with x at x > 0.6. X‐ray magnetic circular dichroism reveals that the large magnetization at x = 0.6 is derived from Fe3+ (3d5) at octahedral sites. The controllable range of the Ec, Hc, and Ms values at room temperature (400–800 kV cm−1, 1–8 kOe, and 0.2–0.6 µB/f.u.) is very wide and differs from those of well‐known multiferroic BiFeO3. Furthermore, the GaxFe2−xO3 films exhibit room‐temperature magnetocapacitance effects, indicating that adjusting TC near room temperature is useful to achieve large room‐temperature magnetocapacitance behavior. GaxFe2−xO3 films simultaneously exhibit room‐temperature out‐of‐plane ferroelectricity and in‐plane ferrimagnetism. The controllable range of the ferroelectric and ferrimagnetic parameters at room temperature is very wide and differs from those of well‐known multiferroic BiFeO3. Furthermore, the films exhibit room‐temperature magnetocapacitance effects, indicating that adjusting TC near room temperature is useful to achieve large room‐temperature magnetocapacitance behavior.