Induction of Strong Magneto-Optical Effect and High Compatibility with Si of BiFeO3 Thin Film by Sr and Ti Co-Doping

The poor magnetic and magneto-optical properties of BiFeO3, along with its significant lattice mismatch with silicon, have limited its application in silicon-based integrated magneto-optical devices. In this study, co-doping with Sr2+and Ti4+ions effectively transformed the trigonal structure of BiFeO3into a cubic phase, thereby reducing the lattice mismatch with silicon to 2.8%. High-quality, highly oriented, silicon-based cubic Sr,Ti:BiFeO3thin films were successfully fabricated using radio frequency magnetron sputtering. Due to the induced lattice distortion, the characteristic periodic spiral spin antiferromagnetic structure of BiFeO3was suppressed, resulting in a significant enhancement of the saturation magnetization of cubic Bi0.5Sr0.5Fe0.5Ti0.5O3(48.0 emu/cm3), compared to that of pristine BiFeO3(5.0 emu/cm3). Furthermore, the incorporation of Sr2+and Ti4+ions eliminated the birefringence effect inherent in trigonal BiFeO3, thereby inducing a pronounced magneto-optical effect in the cubic Sr,Ti:BiFeO3thin film. The magnetic circular dichroic ellipticity (ψF) of Bi0.5Sr0.5Fe0.5Ti0.5O3reached an impressive 2300 degrees/cm.