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Study of Magnetic Excitations in the Spin-Peierls Copper Oxide by Light Scattering

光散射法研究自旋佩尔斯氧化铜的磁激发

基本信息

批准号：
07640494
负责人：
SEKINE Tomoyuki
金额：
$ 1.47万
依托单位：
Sophia University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640494/
关键词：
Raman scattering spin-Peierls transition antiferromagnetic transition spin fluctuation magnetic excitation folded phonon spin gap Fano effect 反強磁性転移フォノン磁気比熱準弾性光散乱 CuGeO_3

项目摘要

1. Quasielastic Light Scattering in CuGeO_3We 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_3We 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_5We 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 PressureHigh-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

1. CuGeO_3中的准弹性光散射我们观察到自旋系统中Tsp以上能量密度涨落的准弹性散射。我们从强度导出了磁比热，并与竞争J模型进行了比较。由准弹性散射的半宽度得到了反相关长度的温度依赖关系. Cu_<1-x>Zn_xGeO_3和CuGe_<1-y>Si_yO_3中的掺杂声子拉曼散射研究了晶格二聚作用下从布里渊区边界折叠到Gamma点的折叠声子的拉曼散射，发现掺杂抑制了自旋Peierls（SP）跃迁，减小了晶格畸变。在反铁磁相中也观察到了这种现象，表明在反铁磁相中存在晶格二聚化现象。在掺杂的CuGeO_3中，选择定则的破坏使我们能够观察到SP能隙激发。随着掺杂剂浓度的增加，它的能量降低并变宽。 ...更多信息随着掺杂浓度的增加，双磁激发束缚态转变为共振态并最终消失。利用绿色函数，考虑到磁激励寿命的缩短，从理论上证明了这些特性.α ′-NaV_2O_5的拉曼散射我们观察到了SP相中的三个折叠声子和磁激发的一级和二级拉曼谱。从极化特性的结果推断了SP相的晶格对称性。α '-Na_ V_2O_5中Na^+离子的缺乏<1-delta>切断了线性自旋链，抑制了SP跃迁，降低了晶格畸变。我们观察到V^<4+>离子的d-d电子拉曼带与V-O弯曲声子之间的Fano效应。这种效应随着Na^+离子缺乏浓度的增加而减弱。考虑到声子-声子弛豫过程，从理论上证明了这些光谱.高压下的拉曼散射为了用拉曼光谱研究高压对SP跃迁的影响，我们安装了金刚石压砧装置。少