Polarized Raman scattering of multiferroic BiFeO3 thin films with pseudo-tetragonal symmetry

Abstract

Polarized Raman scattering study of (001)-oriented epitaxial BiFeO3 (BFO) thin films with pseudo-tetragonal symmetry (4mm) was carried out by employing two distinct backscattering geometries. The A(1)-symmetry transverse-optical [A(1)(TO)] phonons were isolated from the E-symmetry transverse-optical [E(TO)] phonons by using the parallel Y(ZZ)Y-' polarization configuration in a side-view backscattering geometry. With the help of lattice dynamical calculation, we have successfully assigned all the E(TO) and A(1)(TO) normal modes. We found that there was a negligible LO-TO splitting in the A(1) normal modes. This observation suggests that the short-range interatomic force dominates over the long-range coulombic (ionic) force in the pseudo-tetragonal BFO.