Symmetry-mode analysis of the ferroelectric transition in YMnO3

Abstract

Group theoretical methods were applied to elucidate the structural transition path and the polarization process in YMnO3. The atomic displacements derived from in situ high-temperature synchrotron x-ray powder diffraction data were decomposed into three symmetry-adapted modes (Gamma(-)(2); K-1, and K-3). The temperature dependence of the mode amplitudes confirmed the existence of two step-transitions. First, a coupled K-3 and Gamma(-)(2) mode lowered the symmetry from P6(3)/mmc to P6(3)cm at the phase-transition temperature of similar to 1270 K, and held down to the T-C. A single K-3 mode, stabilized by hybridization between the Y and in-plane O ions, operated below T-C with no additional symmetry breakage. (C) 2010 American Institute of Physics. [doi:10.1063/1.3472269]