Anomalous Phonon Behavior in Orthorhombic LuMnO3 at Low Temperature

We present the pressure dependent phonon spectra of orthorhombic-LuMnO3 which are conducted in the low temperature region (below T$_{N}$ and T$_{L})$. A temperature dependent anomalous phonon coincides with the ferroelectric behavior at low pressure condition. At $\sim $10 GPa, this anomalous phonon exhibits an unusual softening trend which will be suppressed at higher pressure. This work is supported by DOE Grant DE-FG02-07ER46402 (NJIT), by DE-FG02-07ER46402 (Rutgers), by COMPRES (U2A beam line at NSLS), the Consortium for Materials Properties Research in Earth Sciences under NSF Cooperative Agreement EAR01-35554, U.S. Department of Energy (DOE-BES and NNSA/CDAC) and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886 (use of NSLS at Brookhaven National Laboratory).