Raman Scattering Study of Sr_<14-x>Ca_xCu_<24>O_<41> : Electronic Properties, etc.

概要

論文の詳細を見る
Polarized Raman scattering spectra of Sr_<l4-x>Ca_xCu_<24>O_<41> have been measured for x = 0 and 11.5 at ambient pressure. In the spectra, the intra-molecular vibrations due to the unit structure of (Sr/Ca)_2Cu_2O_3 and CuO_2 have been clearly observed below 700 cm^<-1>. A comparison of the number of the observed peaks with the results of a factor group analysis indicates that the crystallographic symmetry of the ladder is F_<222> for x = 0 and 11.5, instead of centro-symmetric F_<mmm>, while that of the chain is A_<mma> for both compositions. However the symmetry of the chain for x = 11.5 is close to F_<222> or F_<mmm>. That is, the structure of the chains changes from an incomplete staggered structure to almost complete staggered one with increasing x. In the (c, c) and (a,a) spectra, the broad two-magnon peaks have been observed at around 3000 cm^<-1>. From the analysis of the recent theory of the magnetic scattering in the 2-leg spin ladder system done by Natsume et al., the following magnetic parameters for x = 0 are obtained: J_<leg> = 151 meV J_<rung> = 91 meV, and _<ladder> = 44 meV. The values agree with those reported by neutron scattering.
社団法人日本物理学会の論文
2000-08-15