Ferrimagnetism and Ferroelectricity in Cr-Substituted GaFeO₃ Epitaxial Films

GaFeO 3 -type iron oxides are promising multiferroic materials due to the coexistence of a large spontaneous magnetization and polarization near room temperature. However, magnetic substitution, which is a general method to control multiferroic properties, is difficult due to instability of the substituted GaFeO 3 . In this study, Ga 0.5 Cr 0.5 FeO 3 epitaxial thin films are successfully fabricated through epitaxial stabilization. These films exhibit in-plane ferrimagnetism and out-of-plane ferroelectricity simultaneously. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurements of the Ga 0.5 Cr 0.5 FeO 3 film reveal that the oxidation states of the Fe and Cr ions are trivalent. In addition, some Fe ions are located at tetrahedral Ga1 sites. Compared to the GaFeO 3 film, the Ga 0.5 Cr 0.5 FeO 3 film shows a higher magnetic phase transition temperature (240 K), weaker saturation magnetization at 5 K, and a unique temperature dependence of the magnetization behavior. The effects of Cr substitution on the magnetic properties are strongly affected by the sites of the Fe 3+ (3d 5 ) and Cr 3+ (3d 3 ) ions. Furthermore, room-temperature ferroelectricity in the GaFeO 3 and Ga 0.5 Cr 0.5 FeO 3 films was demonstrated. Interestingly, the change in the ferroelectric parameters via Cr substitution is very small, which disagrees with the previously proposed polarization switching mechanism. Our findings are key to understanding the genuine polarization switching mechanism of the multiferroic GaFeO 3 system.