LATTICE-DYNAMICS OF CR2O3

We present the results of inelastic neutron-scattering experiments for Cr2O3 carried out on the three-axis spectrometers TAS-1 at JAERI (J) and IN1+IN8 at ILL. These experiments allowed us to determine 14 out o f 20 branches along the threefold-axis (Gamma-Z direction) and 10 out of 30 branches along the Gamma-A direction. The collected data are ana lysed on the basis of phenomenological shell models showing convincing agreement between calculation and experiment both for the frequencies and intensities. By a comparison with the Cr2O3 iso-type sapphire Al2 O3 it is found that the dynamical response of the oxygen ion is only s lightly affected by the ionic substitution. The chromium d electrons f ind their expression mainly in a strengthening of the metal oxygen bon ding.