Characterization of the Metallic and Insulating Phase of V₂O₃ and (V,Cr)₂O₃ by XANES

Abstract
We have measured the O Is x-ray absorption of single crystals and epitaxial films of V₂O₃ in both metallic and insulating phases. The spectrum exhibits two peaks, the lower (higher) energy peak due to O 2p contributions to the t_2g (e_g) states. The spectra of all samples in the insulating state vary strongly with the angle between the surface normal and the polarization vector of the incident photons while the spectra of metallic samples are almost isotropic. On cooling t ie single crystal into the insulating phase, the higher energy peak increases in intensity, producing a spectrum similar to that found in the insulating Cr doped and pure V₂O₃ thin films, although the single crystal is then monoclinic while the films are not This implies that the change in the c/a ratio in the transition, not the lattice distortion, is primarily responsible for the change in electronic properties.