1999 Fiscal Year Final Research Report Summary
Thermal induced metal-insulator transition in the titanium oxides single crystals with a high melting point
| Project/Area Number |
10440110
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Hiroshima University |
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Principal Investigator |
IGA Fumitoshi Hiroshima University, Graduate School of Advanced Sciences of Matter, Associate Professor, 大学院・先端物質科学研究科, 助教授 (60192473)
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| Co-Investigator(Kenkyū-buntansha) |
UMEO Kazunori Hiroshima University, Graduate School of Advancred Sciences of Matter, Research Associate, 大学院・先端物質科学研究科, 助手 (10223596)
TAKABATAKE Toshiro Hiroshima University, Graduate School of Advancred Sciences of Matter, Professor, 大学院・先端物質科学研究科, 教授 (40171540)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Mott transiton / metal-insulator transition / orbital order / spin-charge separation / pressure effect / electrical resistivity / photoemission sepectroscopy / Perovskite-type oxide |
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| Research Abstract |
We have studied the mechanism of a metal-insulator (M-I) transition by the magnetic, transport and thermal measurements of YィイD21-xィエD2CaィイD2xィエD2TiOィイD23ィエD2 (x=0.3〜0.4) which exhibits inverse-Mott transition from a metallic state at low temperatures to a semiconducting one at high temperatures.
1. Crystal growth and characterization: We have developed the method of growth for YィイD21-xィエD2CaィイD2xィエD2TiOィイD23ィエD2 single crystals by using an image furnace. Oxygen contents of samples were determined by thermo-gravimetric analysis(TGA) . The results of TGA was used to obtain the best conditions for annealing under flowing oxygen.
2. High-resolution photoemission spectroscopy : We have observed a clear M-I transition in the temperature-dependent photoemission spectra for x=0.39 consistent with transport measurements.
3. Spin-charge separation : In a M-1 transition region, the significant difference in temperature dependences exist between magnetic .susceptibility and electrical resistivity. For a sample in the ferromagnetic region (x=0.05), we have found the stability of an orbital-ordered state a-s for x=0 by spin-polarized neutron diffraction.
4. Future plans : Correlations among the charge , s pin and orbital in YィイD21-xィエD2CaィイD2xィエD2TiOィイD23ィエD2 will be studied by the X-ray diffraction using synchrotron radiation and the spin-polarized neutron diffraction.
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