Ferroelastic domain identification in BiFeO₃ crystals using Raman spectroscopy

Multiferroic BiFeO₃ crystals were investigated by means of micro-Raman spectroscopy using the laser wavelengths of 442 nm (resonant conditions) and 633 nm (non-resonant conditions). The azimuthal angle dependence of the intensity of the Raman modes allowed their symmetry assignment. The experimental data are consistent with a simulation based on Raman tensor formalism. Mixed symmetries were taken into account, considering the orientation of the crystal optic axis along a pseudo-cubic <111> direction. The strong anisotropic intensity variation of some of the polar Raman modes was used for line scans and mappings in order to identify ferroelastic domain patterns. The line scans performed with different excitation wavelengths and hence different information depths indicate a tilt of the domain walls with respect to the sample surface. The domain distribution found by Raman spectroscopy is in very good agreement with the finding of electron back scattering diffraction.