Optical properties of BiFeO3 ceramics in the frequency range 0.3-30.0 THz

Reflection and transmission infrared spectra of BiFeO3 ceramic samples have been measured using submillimeter spectroscopy (on a backward-wave tube spectrometer) and Fourier-transform infrared spectroscopy in the frequency range from 5 to 1000 cm(-1) at temperatures in the range from 10 to 500 K. New resonant modes (probably, magnetic in nature) with the eigenfrequencies decreasing with an increase in the temperature have been recorded in the range 10-30 cm(-1) by IR spectroscopy for the first time. An additional absorption with a fairly large dielectric contribution has been revealed in the range 30-60 cm(-1). It has been demonstrated that the corresponding oscillators couple with both the lowest frequency phonon mode and the magnetic subsystem.