The study of electronic structures for Bi0.95R0.05FeO3 (RÂ =Â Ce, Eu, Er) multiferroic material

Polycrystalline samples Bi0.95R0.05FeO3 (R = Ce, Eu, Er) are prepared by sol-gel method. The result of X-ray diffraction manifests that all samples are in single phase and the structural phase transformation takes place in the Ce substituted samples, and that the crystal symmetry and chemical states of ions differently present in the BiFeO3 multiferroic samples after the substitution of different rare earth ions at Bi sites. The soft X-ray absorption spectroscopy (XAS) experiments at O K- and Fe L3,2-edges are performed to investigate the electronic structure of well-characterized multiferroic samples. And the O1s core level XAS spectra are also recorded to detect the distortion of lattice structure and the change of crystal field symmetry in these compounds. The XAS results indicate the whole valence state of Fe ions for the Er3+ doped sample is higher than that of Ce3+ substituted one. The difference of electronegativity among Ce3+, Eu3+ and Er3+ ions induces the change of Fe2+ content in these doped samples. The enhancement of magnetism for the samples is therefore considered as the result of lattice structure distortion combined with the change of Fe ions whole valence state.