Observation of one magnon and magnon-phonon-electric dipole coupling in multiferroics bismuth ferrite thin films

We observed one magnon, scattering in multiferroic polycrystalline BiFeO3 thin films near 17.2 cm(-1) at 90 K employing Raman spectroscopy. It is seen with a kink in magnon intensity at 150 K and with strong anomaly near 210 K illustrating spin reorientation transition. The spectral weight of one magnon transferred to the lowest phonon mode near the spin reorientation temperature suggests magnon-phonon coupling. Dielectric constant and dielectric loss as function of temperature showed anomaly at 210 K suggesting magnon-phonon-electric dipole coupling. The one magnon becomes overdamped or overcome by elastic scattering at elevated temperatures. (c) 2008 American Institute of Physics.