Structural properties of Bi_1−<i>x</i>La<i>_x</i>FeO₃studied by micro-Raman scattering

Abstract

This paper reports that La-doped BiFeO3 (Bi1−xLaxFeO3, x = 0, 0.1, 0.2, 0.3, 0.6, 0.8 and 1.0) were studied by using micro-Raman spectroscopy and x-ray diffraction (XRD). The XRD patterns indicate that the structure of Bi1−xLaxFeO3 changes from rhombohedral BiFeO3 to orthorhombic LaFeO3. The results of Raman spectroscopy show good agreement with the XRD results. Strikingly, the phonon peak at around 610 cm−1 and the two-phonon peaks in the high frequency range exist in all compounds and enhance with increasing La substitution. The increasing intensity of the 610 cm−1 peak is attributed to the changes in the FeO6 octahedron during the rhombohedral–orthorhombic phase transition. The enhancements of the two-phonon peaks are associated with the breakdown of the cycloid spin configuration with the appearance of the orthorhombic structure. These results indicate the existence of strong spin–phonon coupling in Bi1−xLaxFeO3, which may provide useful information for understanding the effects of La content on the structural and magnetic properties of Bi1−xLaxFeO3.