Infrared spectra and lattice vibrations of the spin-chain

摘要

The infrared spectra of the one-dimensional antiferromagnet LiCuVO_4 are measured in the frequency range from 10 cm~(-1) to 10000 cm~(-1) and at temperatures from 2 K to 300 K, for the electric field vector E of the radiation polarized either along the a- or along the b-crystallographic directions. For each polarization six infrared active phonon modes are observed in accordance with factor group analysis of the crystal structure of LiCuVO_4. The theoretical group analysis of the possible spinel low-symmetry phases is performed within the framework of Landau's theory of phase transitions. The parameters of several phonon lines show noticeable anomalies around 150 K where the magnetic correlations appear in the copper chains, which may indicate a finite interaction between the phonon and the magnon subsystems in LiCuVO_4.