The lattice evolution of the spin-Peierls material CuGeO₃ studied by neutron scattering

CuGeO₃ is an inorganic compound which possesses a spin-Peierls transition. We have studied the crystal structure and the phonon dynamics of CuGeO₃ by neutron scattering. We found that a lattice anomaly starts to evolve significantly above the transition temperature, T_sp, and there is a drastic change below T_sp. The phonon mode over a wide energy range changes drastically at high temperature. Therefore we conclude that the inherent structural instability in the crystal structure provides favorable conditions for the lattice-spin interaction and induces the spin-Peierls transition, i.e. lattice dimerization.