Lattice vibrations of the superconducting oxide spinels

The lattice vibrational spectra of the spinel phases, (x = 0, 0.33) and (y = 0.1, 0.3) (space group , have been measured as a function of temperature and composition by neutron inelastic scattering. Calculations of phonon densities of states (PDOSs) using interatomic potentials were performed and compared with the experimental data. Extensive phonon softening and hardening are observed on Li and Mg substitution throughout the energy range 10 - 100 meV and are discussed in terms of electron - phonon coupling and its relevance to superconductivity. The observed PDOSs show no change on cooling through the superconducting transition temperature, .