Phase Transformations In Multiferroic Bi1-Xlaxfe1-Ytiyo3 Ceramics Probed By Temperature Dependent Raman Scattering

Optical phonons and phase transitions of Bi1-xLaxFe1-yTiyO3 (BLFTO, 0.02 <= x <= 0.12, 0.01 <= y <= 0.08) ceramics have been investigated by Raman scattering in the temperature range from 80 to 680 K. Four phase transitions around 140, 205, 570, and 640K can be observed. The Raman modes are sensitive to the spin reorientation around 140 and 205 K, owing to the strong magnon-phonon coupling. The transformation around 570K is a structural transition from rhombohedral to orthorhombic phase due to an external pressure induced by the chemical substitution. The anomalies of the phonon frequencies near Neel temperature T-N have been discussed in the light of the multiferroicity. Moreover, it was found that the structural transition temperature and T-N of BLFTO ceramics decrease towards room temperature with increasing doping composition as a result of size mismatch between substitution and host cations. (C) 2014 AIP Publishing LLC.