ELASTIC AND INELASTIC NEUTRON STUDY OF CUGEO3

Elastic and inelastic neutron scattering was used to probe the structu ral and magnetic properties of polycrystalline CuGeO3. The diffraction data show that the chemical lattice remains stable in the measured te mperature range 1.5 K less-than-or-equal-to T less-than-or-equal-to 29 6 K. At low temperature the inelastic experiments revealed a well defi ned magnetic excitation at 15 meV, which persists up to T = 50 K. The analysis of the spin-wave spectrum is based on a one-dimensional Heise nberg model within the spin-wave theory. On the other hand, no evidenc e of energy-gap opening, which would result from a dimerization of the Cu chains, could be found at low temperature.