Study of crystal-field excitations and Raman active phonons in o-DyMnO3

In DyMnO3 orthorhombic single crystals, the weak Raman active phonons oftening below T=100 K is correlated with the study of infrared active Dy3+ CF excitations as a function of temperature and under applied magnetic field. We detect five H-13/2 CF transitions that we predict with appropriate CF Hamiltonian and we confirm that the magnetic easy axis lies in the ab plane. While the CF energy level shifts below T=100 K reflect different displacements of the oxygen ions that contribute to the phonon softening, lifting of the ground state Kramers doublet degeneracy (similar to 30 cm(-1)) is observed below T-N=39 K due to the anisotropic Mn3+ -Dy3+ interaction, which could be responsible for the stability of the bc-cycloid ferroelectric phase. (C) 2011 Elsevier B.V. All rights reserved.