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 Ga_xFe_2–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 (E_c) decreases monotonically with x. Additionally, the films show in‐plane ferrimagnetism with a Curie temperature (T_C) >350 K at x = 0–0.6. The coercive magnetic field (H_c) decreases with x at x ≤ 0.6, but shows a constant value at x > 0.6, whereas the saturated magnetization (M_s) 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 E_c, H_c, and M_s values at room temperature (400–800 kV cm^?1, 1–8 kOe, and 0.2–0.6 µ_B/f.u.) is very wide and differs from those of well‐known multiferroic BiFeO₃. Furthermore, the Ga_xFe_2?xO₃ films exhibit room‐temperature magnetocapacitance effects, indicating that adjusting T_C near room temperature is useful to achieve large room‐temperature magnetocapacitance behavior.