IR reflection and absorption spectra of CsDy(MoO4)2 under the cooperative Jahn–Teller effect

IR and far-IR reflection and absorption spectra of a layered CsDy(MoO4)(2) crystal are measured in the temperature range 6-300K. We discuss changes in the phonon spectra at the low-temperature phase transition and the characteristic vibrations, which induce a collective instability of the cooperative Jahn-Teller effect type in CsDy(MoO4)(2) and other layered alkali-rare-earth molybdates. In the discussion of far-IR spectra of CsDy(MoO4)(2), we use the data on RbDy(MoO4)(2) obtained in the frequency range 16-40 cm(-1). Published by AIP Publishing.