Structural distortion and room-temperature ferromagnetization of Co-doped and (Eu, Co)-codoped BiFeO3 nanoparticles

The room temperature ferromagnetism of Co-doped and (Eu, Co)-codoped BiFeO3 nanoparticles has been observed and its origin is investigated by Raman spectra and X-ray absorption fine structure (XAFS). The X-ray diffraction patterns and Raman spectra demonstrate coexistence of orthorhombic and rhombohedral structures in pure BiFeO3 and (Eu, Co)-doped samples. XAFS spectra of Fe K-edge of these samples indicate an increases of the valence state of Fe ions when the Co ions or both Co and Eu ions doped into BiFeO3, and that a large structural distortion is caused by doping, which may be the origin of room temperature ferromagnetism in these two doped samples.

► Ferromagnetism of Co-doped and (Eu, Co)-doped BiFeO3 has been observed.
► Orthorhombic and rhombohedral structures coexist in co-doped BiFeO3.
► XAFS data indicate that the valence state of Fe ions increases in co-doped BiFeO3.
► Larger structural distortion enhances ferromagnetism of the co-doped BiFeO3.