Effects of Y doping on multiferroic properties of sol–gel deposited BiFeO₃ thin films

Polycrystalline BiFeO₃ (BFO), Bi_0.99Y_0.01FeO₃ (BYF1), Bi_0.97Y_0.03FeO₃ (BYF3), Bi_0.95Y_0.05FeO₃ (BYF5) and Bi_0.90Y_0.10FeO₃ (BYF10) thin films have been fabricated on Pt(111)/Ti/SiO₂/Si(100) substrates by sol–gel method. The effects of Y doping on the structural, optical, morphological, ferroelectric and magnetic properties of BFO thin film were analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), ferroelectric and magnetic measurement system, respectively. XRD, Rietveld refinement and Raman analysis demonstrated that the phase of all films was a single perovskite-type rhombohedral structure. A structural transition from the main R3c to the single phase R-3 m was obtained with the BYF10 thin film. SEM showed that the Y doping was beneficial to the crystal growth of BFO films. The ferroelectric test indicated that the Y doping in BYF1 and BYF3 thin films was effective to reduce the leakage current density of the BFO films. The leakage current density of BYF1 thin film was reduced by two orders of magnitude compared to that of the BFO film. The BYF10 thin film had a superior remanent polarization compared to that of other BFO film due to the distorted deformation of FeO₆ octahedra. The magnetic test indicated that a substantially enhanced magnetization was observed in the BYF3 thin film.