Vibrational spectra and force field calculation of A2Mn2O7 (A = Y, Dy, Er, Yb) pyrochlores

Raman and infrared spectra were recorded for A(2)Mn(2)O(7) (A = Y, Dy, Er, Yb) pyrochlores. For the first time, lattice dynamic analysis of cubic manganate pyrochlores was carried out using a short-range force model with four stretching and four bending force constants at the zone center. The assignment of all their modes is proposed. The calculated force constants are discussed and compared for the different pyrochlores. The evaluated wavenumbers are close to the available observed infrared and Raman wavenumbers, giving further support to the present assignments. Copyright (C) 2003 John Wiley Sons, Ltd.