Raman scattering study of charge ordering in beta-Ca0.33V2O5

Abstract

Polarized Raman spectra of the calcium vanadium oxide bronze beta-Ca0.33V2O5 are measured in the temperature range between 300 K and 20 K. The charge ordering phase transition at about 150 K is characterized by the appearance of the new Raman-active modes in the spectra, and by anomalies in the electronic background scattering. The high temperature Raman scattering spectra of beta-Ca0.33V2O5 are in apparent resemblance with those of alpha'-NaV2O5, which suggests that there is a similar charge-phonon dynamics in both compounds. The study of dynamical properties and the symmetry analysis of the Raman modes show that in the mixed valence state of beta-Ca0.33V2O5 the electrons are delocalized into V1-O5-V3 orbitals. We propose that in the charge ordered state below 150 K the d-electrons localize within V1-V3 ladders, either in "zig-zag" fashion like in alpha'-NaV2O5 or in the forms of the double chains like in gamma-LiV2O5.

arXiv comment5 pages, 4 figs incl. in the text. J.Phys.:Condens.Mater 15, (2003) in press

References in corpus (6)

• Infrared and Raman spectra of LiV2O5 single crystals
• First evidence for charge ordering in NaV${}_2$O${}_5$ from Raman spectroscopy
• Pressure dependence of phase transitions in the quasi one-dimensional metal-insulator transition system beta-Na1/3V2O5
• Optical properties of NaxV2O5
• Charge-ordering and optical transitions of LiV2O5 and NaV2O5
• Charge excitations in LiV${}_2$O${}_5$ and NaV${}_2$O${}_5$: similarities and differences

Cited by in corpus (3)

• Leading interactions in the $\beta$-$Sr{V}_6{O}_{15}$ compound
• Pressure-induced changes in the optical properties of quasi-one-dimensional $\beta$-Na${}_{0.33}$V${}_2$O${}_5$
• Investigation of lattice dynamics, magnetism and electronic transport in $\beta$-Na${}_{0.33}$V${}_2$O${}_5$