2009 Fiscal Year Final Research Report
A new stages of the anisotropic extension for the fragile molecular solids, the charge ordering and the superconducting transition
| Project/Area Number |
20850024
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| Research Category |
Grant-in-Aid for Young Scientists (Start-up)
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| Allocation Type | Single-year Grants |
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| Research Field |
Functional materials chemistry
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| Research Institution | Osaka University |
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Principal Investigator |
YAMAMOTO Takashi Osaka University, 大学院・理学研究科, 助教 (20511017)
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| Project Period (FY) |
2008 – 2009
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| Keywords | 分子凝縮体 / 延伸下物性測定法 / 特殊環境下に対応した材料開発 / 超伝導機構 / 電荷整列 / スピンフラストレーション / 分子内振動 / 電荷揺らぎの相分離 |
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| Research Abstract |
(1) In the field of condensed molecular solids, the anisotropic extension is the new method exploring the notable phase transition. In the previous study, we have developed the methodology observing the temperature dependence of the electrical resistivity under the anisotropic extension and the magnetic field. As a next step, the measurement of the magnetic susceptibility has been tried. The epoxy resin often used for the low temperature physics is not appropriate for our purpose because of the chemical reaction with the sample crystal. The chemical reaction can be avoided by using another kind of resin for sample coating. Nevertheless, we find that this method is not suitable for the magnetic susceptibility measurement, because the sample is separated from the epoxy rod when the extension is applied to the epoxy rod. We have started from examining the resin which is free from chemical reaction and sample coating. We have found that the resin made from some chemicals satisfies above re
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quirements. By using above resin and sample crystals, the temperature dependence of the magnetic susceptibility was successfully measured.
(2) The conducting molecular solids are roughly classified into two groups from the viewpoint of the structures of two-dimensional layer. In one group, two-dimensional layer consists of a tight dimer. In the other group, a loose dimer contributes to the two-dimensional layer. As for the former group, the role of charge and lattice have not been examined so far whereas the magnetic interaction is intensively studied. A series of [Pd(dmit)_2]_2X is a good model compound because not only anti-ferromagnetic state, characteristic of the tight dimer syatem, but also non-magnetic insulator state. We have developed the methodology evaluating the roles of charge and lattice in [Pd(dmit)_2]_2X using vibrational spectroscopy. After confirmation of the methodology, we have applied thevibrational spectroscopy to the some materials exhibiting the spin-liquid behavior and the phase transition from non-magnetic insulator to superconducting state. We have found that the electron-electron interaction and the electron-phonon interaction play an important roles in the physical properties of above materials. We have also observed vibrational spectra of the K?type ET salt exhibiting the spin-frustration. The experimental results strongly suggest the important role of the electron-electron interaction and the electron-phonon interaction in the ground state. These observations imply that the conducting and magnetic properties for both tight dimer and loose dimer materials can be understood from the generalized mechanism."
(3) The charge ordered transition requires the inter-molecular Coulomb interaction and an additional interaction. In the previous study, we have shown that the secondary strong Coulomb interaction and the electron-phonon interaction become an additional interaction. In order to explore other additional interaction, we have examined the role of the hydrogen bond using the molecular conductor containing an amide-group, which is synthesized by Prof. Batail's group. Applying the vibrational spectroscopy to the present material, we have found that the anti-ferromagnetic state is the charge ordering state. The observed spectra indicates the hydrogen bond can participate in the phase transition. Less
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