Pressure dependence of far-infrared reflectance spectra in layered iron oxide LuFe₂O₄

Abstract

The far-infrared reflectance spectra of layered iron oxide LuFe₂O₄ have been investigated at external pressure up to 8 GPa. The observed phonon modes continuously shift to the higher energy side with increasing pressure below 6 GPa. However, it is found that the spectral profile of the phonon modes drastically changes around 6 GPa. From the analysis of the phonon modes using a Lorentz oscillator model, it is shown that the spectral changes correspond to a structural phase transition that occurs at 6 GPa.