Polar phonons and spin excitations coupling in multiferroic BiFeO3 crystals

Raman scattering measurements on BiFeO3 single crystals show an important coupling between the magnetic order and lattice vibrations. The temperature evolution of phonons shows that the lowest energy E and A(1) phonon modes are coupled to the spin order up to the Neel temperature. Furthermore, low temperature anomalies associated with the spin reorientation are observed simultaneously in both the E phonon and the magnon. These results suggest that magnetostriction plays an important role in BiFeO3.