50 150 250 350 450 550 650 273 223 173 163 153 143 133 123 81 Int. (arb. units) Raman shift (cm$^{-1}$) BFO(001) thin film 81-273 K (a) 50 100 150 200 250 300 0 1 2 3 4 0 2 4 6 8 10 F requency variation (cm -1 ) Temperature (K)  Peak 1  Peak 3 (b)  Peak 2 50 100 150 200 250 300 4 5 6 7 8 9 12 15 18 21 24 FWHM (cm -1 ) Temperature (K)  Peak 1  Peak 3 (c)  Peak 2 6 FIG. 3: (a) Temperature dependent Raman spectra of (001)BFO film on SRO/STO from 81K-RT; (b) and (c) temperature dependence of phonon frequencies variation and FWHM for 72 (peak 1), 140 (peak 2), and 171 (peak 3)cm − 1 down to 81K from RT, respectively. the comparative study with the thin film and G. Cata- lan, University of Cambridge for his useful comments and suggestions. We thank Brahim Dkhil for sharing his Ra- man data on phonon anomalies in BFO single crystals near 140K prior to their publication. The authors would like to acknowledge financial sup- port from DOE DE-FG02-08ER46526 grant. RP thanks Institute of Functional Nanomaterial (IFN), UPR for fi- nancial support. at around 820 ◦ C and no softening of Raman modes was observed at low frequencies, as in BFO single crystals. The AFM-PM phase transition at around 370 ◦ C caused some small changes in the phonon frequencies, linewidth, and/or intensities of several low frequency modes, in- dicating ME coupling in the material. A non-cubic γ - BiFeO$_{3}$ phase was observed between 931-950 ◦ C in the BFO thin films, in agreement with the accepted BiFeO$_{3}$ phase diagram. The spectra also revealed an evidence of a cubic δ -phase around 1000 ◦ C in thin films that is not stable in powder and bulk. The authors are grateful to Prof. Hans Schmid, Uni- versity of Geneva for supplying BFO single crystal for Ramesh, Nature Mat., 5 , 823 (2006). ACKNOWLEDGEMENT [1] D.C. Arnold, K.S. Knight, F.D. Morrision, and P. Light- foot, Phys. Rev. Lett. 102 , 027602 (2009). [2] D C Arnold, P. Lightfoot, G. Catalan, J. F. Scott, and F D Morrison, Phys. rev. B (2009) in press . [3] O.E. Gonzalez-Vasquez and J. Iniguez, Phys. Rev. B. 79 , 064102 (2009). [4] H. Schmid, Ferroelectrics 162 , 317 (1994). [5] M. Fiebig, T. Lottermoser, D. Fr¨ o hlich, A.V. Goltsev,and R.V. Pisarev, Nature 419 , 818 (2002). [6] J. Wang, J. B. Neaton,H. Zheng, V. Nagarajan, S. B. Ogale, B. Liu, D. Viehland, V. Vaithyanathan, D. G. Schlom, U. V. Waghmare, N. A. Spaldin,K. M. Rabe, M. Wuttig, and R. Ramesh, Science 299 , 1719 (2003). [7] Y. Tokura, Science 312 , 1481 (2006). [8] J.F. Scott, Nature Materials 6 , 256 (2007). [10] Y.H. Chu, M. P. Cruz, C.H. Yang, L. W. Martin, P.- L. Yang, J.-X. Zhang, K. Lee, P. Yu, L.-Q. Chen, R. Ramesh, Advn. Mat., 19 , 2662 (2007). [11] N.A. Hill, J. Phys. Chem. B 104 , 6694 (2000). [12] I. Sosnowska, T. Peterlin-Neumaier, and E. Steichele, J. Phys. C 15 , 4815 (1982) [13] G.A. Smolenskii and I. Chupis, Sov. Phys. Usp. 25 , 475 (1982). [14] C. Tabares-Munoz, J.P. Rivera, and H. Schmid, Ferro- electrics 55 , 235 (1984). [15] R. Palai, R.S. Katiyar, H.S. Schmid, P. Tissot, S.J. Clark, J. Robertson, S.A.T. Redfern, G. Catalan, and J.F. Scott, Phys. Rev. B 77 , 014110 (2008) [16] F. Kubel and H. Schmid, Acta Crystallogr. Sect. B: Struct. Sci. 46 , 698 (1990). [17] J.D. Bucci, B.K. Robertson, and W.J. James, J. Appl. Cryst. 5 , 187 (1972). [9] T. Zhao, A. Scholl, F. Zavaliche, K. Lee, M. Barry, A. Doran, M. P. Cruz, Y. H. Chu, C. Ederer, N. A. Spaldin, R. R. Das, D. M. Kim, S. H. Baek, C. B. Eom, and R.