Magnetic-Field-Tunable Intensity Transfer from Optically Active Phonons to Crystal-Field Excitations in the Reflection Spectra of the PrFe3(BO3)4 Antiferromagnet

We analyze the field-dependent intensities of the coupled electron-phonon modes observed in the low-temperature far-infrared (terahertz) reflection spectra of PrFe3(BO3)4 and develop a theory based on the Green’s function approach. An excellent agreement between the experimental and theoretical data is achieved. The developed theory of the intensity transfer from phonons to quasi-electronic excitations can be applied to the electron-phonon modes in other compounds, in particular, in magnetodielectric materials, where it can be used to analyze the magnetodielectric response.