Cold Neutron Inelastic Scattering Measurements of the Spin-Peierls and Antiferromagnetic Excitations in Si-doped CuGeO_3 Single Crystals : Condensed Matter: Structure, etc.

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Cold neutron inelastic scattering experiments on four CuGe_<1-x>Si_xO_3 single crystals with x=0, 0.004, 0.01, and 0.02 have been performed to study the effects of Si doping on the antiferromagnetic (AFM) and spin-Peierls (SP) excitations with high energy resolution. The intrinsic energy width Γ of the AFM excitation measured along the c^* ([001]) direction near the magnetic zone center (0, 1, 1/2) (q=0) varies as q^2 for q ⪇ 0.032 Å^<-1>=0.06qZB. This observation directly supports the recent theoretical predictions of Saito and Fukuyama. For pure CuGeO_3 the intrinsic SP excitation energy width appears to be resolution-limited up to 0.085 Å^<-1>. Upon doping, the widths of the SP excitations increase dramatically, but they are weakly q-dependent in the range we investigated. At x=0.02 the SP phase if lost. The existence of a second gap in CuGeO_3, first observed by Ain et al., is also confirmed. This second gap, which is quite sharp in the pure compound, is considerably broadened at Si concentrations as low as x0.004.
社団法人日本物理学会の論文
2000-02-15