Electric-dipole and magnetic absorption in TbFeO₃ single crystals in the THz-IR range

Various mechanisms of absorption including both electric-dipole excitations and magnetic ones in a broadband (5-5000 cm(-1)) polarized transmission and reflection spectra were studied in orthoferrite TbFeO3 using a coherent submillimeter, pulsed THz, and IR Fourier transform spectroscopy. The classical oscillator model and generalized four-parameter model were used to analyze the spectra obtained, and the parameters of the models were determined. We analyzed main absorption processes, which include contributions of both phonons and multi-phonon processes as well as electron transitions in Tb3+ ions and two antiferromagnetic resonance modes in the Fe subsystem. As a result, the spectra of real and imaginary parts of permeability and permittivity were obtained. A distinctive feature of the studied electrodynamic response in TbFeO3 is a significant absorption in the THz range due to multi-phonon processes, which exceeds optical phonon contribution by an order of magnitude at room temperature.