Anomalous magnetic ordering induced spin-phonon coupling in BiFeO3 thin films

Abstract

Low-temperature magnetic properties and Raman spectra of epitaxial BiFeO3 (BFO) thin films, grown on (111)SrTiO3 substrates, have been studied. For all three prominent A(1)-symmetry Raman modes(138,170, and 214cm(-1)), there was a good linear correlation between the mode-frequency softening and the square of the in-plane magnetization in the temperature range between 80 and 300 K. These observations were ascribed to the spin-phonon coupling below the Neel temperature (T-N = 643 K). The observed anomalous enhancements in Raman intensity below 200 K reveal spin reorientation transition due to change in the magnetic spin ordering. (C) 2009 Elsevier Ltd. All rights reserved.