2006 Fiscal Year Final Research Report Summary
Spectroscopic Studies on Mechanism of Metal-Insulator Transition of Titanium and Vanadium Oxides
| Project/Area Number |
17540329
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
SATO Hitoshi Hiroshima University, Hiroshima Synchrotron Radiation Center, Associate Professor, 放射光科学研究センター, 助教授 (90243550)
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| Co-Investigator(Kenkyū-buntansha) |
SAWADA Masahiro Hiroshima University, Hiroshima Synchrotron Radiation Center, Assistant, 放射光科学研究センター, 助手 (00335697)
IGA Fumitoshi Hiroshima University, Graduate School of Advance Sciences of Matter, Associate Professor, 大学院先端物質科学研究科, 助教授 (60192473)
TANAKA Arata Hiroshima University, Graduate School of Advance Sciences of Matter, Assistant, 大学院先端物質科学研究科, 助手 (70253052)
TANIGUCHI Masaki Hiroshima University, Graduate School of Science, Professor, 大学院理学研究科, 教授 (10126120)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Metal-Insulator Transition / Ti_2O_3 / XAS / LD / 3d electron configuration |
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| Research Abstract |
Recently, Tanaka proposed a new unified model for a mechanism of Metal-Insulator Transition (MIT) for Ti_2O_3 and VO_2 [1]. In case of Ti_2O_3, MIT takes place around 450 K from an insulating phase at low temperatures to a metallic phase at high temperature phase. In his model, in accordance with MIT, a Ti 3d electron configuration of the Ti ion pair changes from (a_<1g>↑ ; a_<1g>↓) to (a_<1g>↑; e_g(π)↑) and this change leads to MIT of Ti_2O_3. The mechanism of MIT for VO_2 is also interpreted based on the same scenario. He also pointed out that such a change of the electronic configuration is clearly observed in the Ti 2p-3d x-ray absorption spectra and its linear dichroism (XAS/LD).
In the present study, we have grown Ti_2O_3 single crystals and carried out the Ti 2p-3d XAS/LD experiments between 300 K (insulating phase) and 520 K (metallic phase) on the beamline BL14 of HiSOR, Hiroshima Synchrotron Radiation Center. The XAS spectra show a remarkable LD, reflecting an anisotropy of the Ti 3d states. The LD intensity at 520 K is reduced to 60 % relative to that at 300 K, which indicates a decrease of the anisotropy of the Ti 3d states. The multiplet analyses for the XAS/LD spectra give that (a_<1g>↑; a_<1g>↓) : (a_<1g>↑ ; e_g(π)↑) = 0.55:0.45, 0.15:0.85 at 520 and 300 K, respectively. The LD intensity changes only around MIT temperature, indicating that the change of the Ti 3d electronic configuration is related to MIT. These results support the MIT model proposed by Tanaka [1]. We have also found the change of the Ti 3d states from the O ls XAS spectra. In addition, the Ti 2p soft x-ray emission spectra exhibit an elastic peak only at metallic phase.
[1] A. Tanaka, J. Phys. Soc. Jpn. 73, 152 (2004).
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Research Products
(12 results)
