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

点击翻译按钮获取中文摘要

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