The spectra of far-infrared transmission in Tb3Fe5O12 magnetoelectric single crystals have been studied in the range between 15 and 100 cm-1, in magnetic fields up to 10 T, and for temperatures between 5 and 150 K. We attribute some of the observed infrared-active excitations to electric-dipole transitions between ligand-field split states of Tb3+ ions. Anticrossing between the magnetic exchange excitation and the ligand-field transition occurs at the temperature between 60 and 80 K. The corresponding coupling energy for this interaction is 6 cm-1. Temperature-induced softening of the hybrid IR excitation correlates with the increase of the static dielectric constant. We discuss the possibility for hybrid excitations of magnons and ligand-field states and their possible connection to the magnetoelectric effect in Tb3Fe5O12.
@article{arxiv.1005.2705,
title = {Coupling between magnon and ligand-field excitations in magnetoelectric Tb3Fe5O12 garnet},
author = {T. D. Kang and E. Standard and K. H. Ahn and A. A. Sirenko and G. L. Carr and S. Park and Y. J. Choi and M. Ramazanoglu and V. Kiryukhin and S-W. Cheong},
journal= {arXiv preprint arXiv:1005.2705},
year = {2015}
}