| Project/Area Number |
12450264
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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 |
Inorganic materials/Physical properties
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
ITOH Mituru Tokyo Institute of Technology, Materials and Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (30151541)
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| Co-Investigator(Kenkyū-buntansha) |
KYOMEN Toru Tokyo Institute of Technology, Materials and Structures Laboratory, Research Assistant, 応用セラミックス研究所, 助手 (10323841)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥15,100,000 (Direct Cost: ¥15,100,000)
Fiscal Year 2001: ¥5,300,000 (Direct Cost: ¥5,300,000)
Fiscal Year 2000: ¥9,800,000 (Direct Cost: ¥9,800,000)
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| Keywords | quantum effect / isotope exchange / ferroelectricity / quantum paraelectric / field effect / spin crossover / perovskite / MI-transition / 量子常誘電体 / 強誘電体 / 光誘起効果 / 電荷整列 / ナノドメイン / 電場効果 / 強磁性 / 反強磁性 / 電気伝導性 |
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| Research Abstract |
Evolution of the gigantic effects was attempted by the control of quantum fluctuations both in dielectrics and paramagnetics. Finally, gigantic quantum effect was found, for the first time, in quantum paraelectric SrTiO_3, KTaO_3, and CaTiO_3. Also metal-insulator transition due to spin crossover was successfully found in cobalt perovskite. These two results are quite important in the solid state physics and many researchers are following our experiments.
The key points are summarized as follows.
1. Oxygen isotope exchange induces a transition from quantum paraelectric to quantum ferroelectric. Quite large voltage dependence appears in the vicinity of critical composition of 33 % exchange. Ferroelectric soft mode was found for the first time by the hyper-Raman scattering. Small bias and irradiation of UV light for the Quantum paraelectrics, SrTiO_3, KTaO_3, and CaTiO_3, induces a new quantum state, which gives a gigantic dielectric constant.
2. Spin crossover in cobalt ions was successfully controlled by the charge and orbital ordering in perovskite-type oxides. The phase transition due to the spin crossover was found to be first order-type, accompanying a large volume change, a metal-insulator transition, and a paraelectric-nonmagnetic transition. This is the first example of the spin crossover in perovskites.
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