Magnetic Excitations in the Si Doped Spin-Peierls Compound CuGe_1-xSi_xO₃

Abstract

The magnetic excitations of CuGe_1-xSi_xO₃ single crystals(x=0.011 and 0.03) have been studied by inelastic neutron-scattering techniques. We confirm the coexistence of the antiferromagnetic and spin-Peierls excitations as well asa splitting of the antiferromagnetic excitation peak at the magnetic zone center (q=0)due to orthorhombic anisotropy. The q dependence of the antiferromagnetic spin-wave widthΓ scales well with q² for small q (q<0.1 Å^-1). We also find thatthe spin-wave velocity increases as the size of induced magnetic moment becomes larger. These experimental results strongly support recent theoretical predictions by Saito andFukuyama.