1990 Fiscal Year Final Research Report Summary
Spectroscopic Study on Dynamical Properties of Solitons in Quasi One-Dimensional Platinum Complexes
| Project/Area Number |
63460025
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Tohoku University |
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Principal Investigator |
KURODA Noritaka I. M. R., Tohoku Univ., Associate Professor, 金属材料研究所, 助教授 (40005963)
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| Co-Investigator(Kenkyū-buntansha) |
NISHINA Yuichiro I. M. R., Tohoku Univ., Professor, 金属材料研究所, 教授 (90005851)
SAKAI Masamichi I. M. R., Tohoku Univ., Assistant, 金属材料研究所, 助手 (40192588)
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| Project Period (FY) |
1988 – 1990
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| Keywords | Linear-Chain Platinum Complex / Soliton / Mesoscopic Defect / Dynamical Properties / Hopping Motion / Diffusion / Optical Absorption / Electron Paramagnetic Resonance |
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| Research Abstract |
Irradiation of halogen-bridged linear-chain platinum complex by near band-gap light produces mesoscopic defects of valance alternation peculiar to one-dimensional materials with a strong electron-phonon coupling. We have carried out systematic experiments of optical absorption, Raman scattering, and electron paramagnetic resonance in UV irradiated (Pt(en)_2) (Pt(en)_2Cl_2) (C10_4)_4 (en=ethylenediamine) to identify the valence structure of the optically induced defects and to clarify their dynamical properties which have never been studied before.
Detailed analyses of the spectra obtained have led us to conclude that the lowest-entry state of the defect is the spin soliton with S = 1/2. Its valence structure can be regarded as an ideal dimer of Pt ions, and thus its size is as small as about 1 nm. At liquid He temperatures the spin solitons are fluctuating around their equilibrium positinos. At higher temperatres, however, they undergo the translational motin due to hopping along the linear-chain of mixed-valent platinum ions. The activation energy of the hopping motion is as low as 13 meV, so that the correlation rate amounts to 10^9 sec^<-1> at room temperature. They may also diffuse across the chains at elevated temperatures. The life time of the spin soliton is very long, probably longer than several ten hours, as far as the crystal is kept at a certain temperature below 100 K. Nevertheless, the number of spins varies reversibly if the temperature is varied. These observations indicate that the spin solitons are equilibrated thermally with a nonmagnetic state which lies in energy about 14 meV above the spin solitons. On the basis of the one-dimensional Mott-Hubbard model, our spectroscopic information on the electron-phonon coupling energy and the transfer integral suggests that this nonmagnetic state is the charged soliton.
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