Structural properties of Bi1-xLaxFeO3 studied by micro-Raman scattering

This paper reports that La-doped BiFeO₃ (Bi_1-xLa_xFeO₃, x=0, 0.1, 0.2, 0.3, 0.6, 0.8 and 1.0) werestudied by using micro-Raman spectroscopy and x-ray diffraction(XRD). The XRD patterns indicate that the structure of Bi_1-xLa_xFeO₃ changes from rhombohedral BiFeO₃ toorthorhombic LaFeO₃. The results of Raman spectroscopy showgood agreement with the XRD results. Strikingly, the phonon peak ataround 610~cm^-1 and the two-phonon peaks in the highfrequency range exist in all compounds and enhance with increasingLa substitution. The increasing intensity of the 610~cm^-1peak is attributed to the changes in the FeO₆ octahedron duringthe rhombohedral--orthorhombic phase transition. The enhancements ofthe two-phonon peaks are associated with the breakdown of thecycloid spin configuration with the appearance of the orthorhombicstructure. These results indicate the existence of strongspin--phonon coupling in Bi_1-xLa_xFeO₃, which mayprovide useful information for understanding the effects of Lacontent on the structural and magnetic properties of Bi_1-xLa_xFeO₃.