Coupling between magnon and ligand-field excitations in magnetoelectric Tb3Fe5O12 garnet

TL;DR

This study investigates the interaction between magnon and ligand-field excitations in Tb3Fe5O12, revealing hybrid modes and their potential link to magnetoelectric effects through infrared spectroscopy under varying temperature and magnetic fields.

Contribution

It provides the first detailed analysis of magnon-ligand-field coupling in Tb3Fe5O12, demonstrating anticrossing behavior and hybrid excitations relevant to magnetoelectric phenomena.

Findings

Anticrossing between magnetic and ligand-field excitations at 60-80 K.

Coupling energy of 6 cm-1 between magnon and ligand-field states.

Temperature-induced softening correlates with dielectric constant increase.

Abstract

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.