We report an x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) study on K2V8-xTixO 16 (x=0.0, 0.3, and 4.0) in which the metal-insulator transition (MIT) and the tetragonal-to-monoclinic structural transition show different responses against the Ti doping. The spectral change of V 2p XAS across the MIT is similar to that observed in VO2, indicating that the V-V pairing is responsible for the MIT. In the insulating phase, the V 2p XPS spectra are split into the V3+ and V4+ features showing the localized character of the V 3d electrons. In addition, the V 2p XAS spectra of the monoclinic insulating phase suggest that the V-V pairing is weakened, and, instead, the V3+-V4+ coupling is strengthened by orbital ordering. In contrast to VO2, the existence of the V3+ component in K2V8-xTixO16 gives additional orbital instability in the insulating phase, which competes with the V-V pairing.
|ジャーナル||Physical Review B - Condensed Matter and Materials Physics|
|出版ステータス||Published - 2011 3 22|
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