Dynamical effects of the interaction between 4f electrons and optical phonons in rare-earth hydroxides, especially in Tb(OH)3and Nd(OH)3

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Abstract
The Raman spectra of single crystals of Nd(OH)3, Gd(OH)3, Tb(OH)3 and of Y(OH)3 have been investigated at helium temperatures and partially in external magnetic fields B3 all these effects can be observed simultaneously. In the same crystal the magnetic phonon splitting occurs spontaneously below its ferromagnetic Curie temperature. All effects can be treated theoretically using a Jahn-Teller type interaction Hamiltonian bilinear in the electron and phonon variables. The numerical values of the coupling constants have been found to agree for the different interaction effects. There are indications of a systematic variation of these numbers with the type of rare-earth ion and the phonon mode considered. The contribution of optical phonons to the effect of interionic energy transfer in Tb(OH)3 by virtual phonon exchange is considered and compared with the aforementioned results.