One-magnon light scattering and spin-reorientation transition in epitaxial BiFeO3 thin films

Raman scattering from one-magnon excitation has been observed for the first time in epitaxial BiFeO3 thin films grown on (111) SrTiO3 substrates. The intensities and the frequency of the magnon mode at 18.9 cm(-1) (M-1) showed a discrepancy at the characteristic temperatures of similar to 140 and 200 K and the magnon mode at 27.9 cm(-1) (M-2) disappeared at similar to 200 K suggesting spin-reorientation (SR) transition in the epitaxial BFO film. The dc susceptibility measurement showed a large discrepancy near these two temperatures evidently elucidating the spin-reorientation transition mechanism. The partial spectral weight of the magnon modes is believed to be transferred to the lowest phonon mode appearing at 72.8 cm(-1) and higher magnon mode M-2 disappearing near 200 K reveal magnon-phonon coupling near to SR transition. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.