Deviation from the Curie-Weiss law in KTa1−xNbxO3at high temperature

Abstract
Infrared reflection spectra performed by scanning interferometry on a KTa0.982Nb0.018O3 crystal are reported from room temperature up to 1300 K. A significant deviation of the soft mode behavior from the Curie-Weiss law is evidenced with increasing temperature. Furthermore, the soft (TO) mode is found to be strongly coupled with the next low-frequency TO mode.