Raman, infrared and optical spectra of the spin-Peierls compound NaV_2O_5

TL;DR

This study investigates the polarized Raman, infrared, and optical spectra of NaV_2O_5 crystals above the spin-Peierls transition, revealing spin-phonon interactions and electronic transition features.

Contribution

First detailed polarized spectral measurements of NaV_2O_5 above Tsp, identifying spin-phonon coupling effects and electronic transition characteristics.

Findings

Observation of asymmetric FIR phonon lines due to spin-phonon interaction

Detection of broad bands in Raman and FIR spectra possibly related to electronic or magnetic excitations

Identification of vanadium d-d transitions and charge-transfer absorption edges

Abstract

We have measured polarized spectra of Raman scattering, infrared and optical transmission of NaV_2O_5 single crystals above the temperature of the spin-Peierls transition Tsp=35 K. Some of the far-infrared (FIR) phonon lines are strongly asymmetric, due to the spin-phonon interaction. In addition to the phonon lines, a broad band was observed in the c(aa)c Raman spectrum and in the E||a FIR transmission spectrum. A possible origin of these bands is discussed. The absorption band at 10000 cm-1 1.25 eV is attributed to vanadium d-d electronic transitions while the absorption edge above 3 eV is supposed to correspond to the onset of charge-transfer transitions.