Phase Transition and V4+-V4+ Pairing in VO2(B)

✍ Scribed by Yoshio Oka; Takeshi Yao; Naoichi Yamamoto; Yutaka Ueda; Akihiko Hayashi

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 251 KB
• Volume: 105
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1215

✦ Synopsis

The study of low-temperature X-ray diffraction and magnetic properties of (\mathrm{VO}{2}(B)) has revealed a structural phase transition and formation of (\mathrm{V}^{4+}) ion pairs. The phase transition occurs over a temperature range from 300 to (180 \mathrm{~K}); however, a complete structural change is not attained. The lowtemperature phase has the same monoclinic symmetry as the high-temperature phase. The X-ray Rietveld refinements revealed a significant decrease in the (V(2)-V(2)) distance from 0.2867 to 0.2670 (\mathrm{nm}), indicating (\mathrm{V}^{4+}-\mathrm{V}^{4+}) pairing for half of the (\mathrm{V}) sites in the low-temperature phase. The pairing has been confirmed by the observation of a spin-singlet state in the ({ }^{5 / V}) NMR measurements and corresponds to the decrease in magnetic susceptibility. The behavior of phase transition and pairing in (\mathrm{VO}{2}(\mathrm{~B})) are analogous to those in (\mathrm{V}{6} \mathrm{O}{13}), which has a related structure. 1993 Academic Press, Inc.