Highly bulk-sensitive hard x-ray photoemission has been performed for the Magnéli phase V5 O9 and V6 O11, which are composed of V2 O3 and VO2 from chemical point of view. The valence-band spectra near the Fermi level are rather similar between V5 O9 and V6 O11 in both metallic and insulating phases. Although the core-level spectra in the metallic phase are similar between V5 O9 and V6 O11, the core-level spectra in the insulating phase are noticeably different. Our results are understood by considering the contribution of the V-V dimerization effects, which are strong in V6 O11 and negligible in V5 O9. Comparison of the core-level spectra of V5 O9 and V6 O11 with those of VO2 has revealed that the mechanism of the metal-insulator transitions for the former two compounds is different from that for VO2.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 2010 Mar 22