Eur. Phys. J. B 54, 67-72 (2006)
https://doi.org/10.1140/epjb/e2006-00419-y

Raman study of orbital mediated multiphonons in RMnO₃ (R = Pr,Sm,Eu,Tb,Y)

¹ Département de Physique, Université de Sherbrooke, J1K 2R1, Sherbrooke, Canada
² General Physics Institute, Russian Academy of Sciences, 119991 Moscow, Russia

Corresponding author: ^a Jonathan.Laverdiere@USherbrooke.ca

Received: 16 July 2006
Revised: 25 September 2006
Published online: 29 November 2006

Abstract

We have studied RMnO₃ manganites (R = Pr, Sm, Eu, Tb, Y) Raman excitations in the 200–2800 cm^-1 range as a function of temperature. Combinations of phonon energies are observed up to the fourth order, indicating the presence of electron-phonon coupling. In comparison to Γ-point phonon combinations, double phonon excitations appear to be blue shifted in large size rare earth ion compounds. The phonon combination intensities decrease rapidly with their increasing order, confirming other studies which conclude that the electron-phonon coupling is not as strong as supposed in the localized limit. Moreover, different intensity order dependences are observed between the phonon combination and the so-called Jahn-Teller mode. These effects are better described in the orbiton-phonon coupling scheme.