1996 Fiscal Year Final Research Report Summary
Study of Magnetic Excitations in the Spin-Peierls Copper Oxide by Light Scattering
| Project/Area Number |
07640494
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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 |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Sophia University |
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Principal Investigator |
SEKINE Tomoyuki Sophia University, Department of Physics, Professor, 理工学部, 教授 (60110722)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Hidekazu Tokyo Institute of Technology, Department of Physics, Associate Professor, 理学部, 助教授 (80188325)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Raman scattering / spin-Peierls transition / antiferromagnetic transition / spin fluctuation / magnetic excitation / folded phonon / spin gap / Fano effect |
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| Research Abstract |
1. Quasielastic Light Scattering in CuGeO_3
We observed quasielastic scattering from the fluctuations of the energy density above Tsp in the spin system. We derived the magnetic speciflc heat from the intesity and compared it with a competing-J model. The temperature dependence of the inverse correlation length was obtained from the half width of the quasielastic scattering.
2. Doping Effects-Raman Scattering in Cu_<1-x>Zn_x GeO_3 and CuGe_<1-y>Si_yO_3
We studied Raman scattering from the folded phonon, which was folded onto GAMMA point from the Brillouin zone boundary by the lattice dimerization, and found that the doping suppressed the spin-Peierls (SP) transition and reduced the lattice distortion. We also observed it even in the antiferromagnetic phase, indicating the existence of the lattice dimerization in this phase. Breakdown of the selection rule in the doped CuGeO_3 enabled us observe a SP gap excitation. It decreased in energy and broadened with increasing dopant concentration.
… More
The two-magnetic-excitation bound state changed into a resonant state and finally disappeared with increasing dopant concentration. These features were demonstrated theoretically by using Green's function, taking into account the shortening of the lifetime of the magnetic excitations.
3. Raman Scattering in alpha'-NaV_2O_5
We observed three folded phonons and the first-and second-order Raman spectra from magnetic excitations in the SP phase. We infered the lattice symmetry of the SP phase from the results of the polarization characteristics. The Na^+-ion deficieney in alpha'-Na_<1-delta>V_2O_5 cut the linear spin chain, and it suppressed the SP transition and reduced the lattice distortion. We observed the Fano effect between the V-O bending phonon and the d-d electronic Raman band of the V^<4+> ion. This effect weakened with increasing concentration of the Na^+-ion deficiency. These spectra were demonstrated theoretically, taking into account a phonon-phonon relaxation process.
4. Raman Scattering under High Pressure
High-pressure equipment of the diamond anvil cell has been installed in order to study the high-pressure effect on the SP transition by means of Raman spectroscopy. Less
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