  Neutron inelastic scattering studies on aligned crystals of NaxCoO2.yD2O have
been carried out. Significant scattering has been observed for phonons
originating from the vibrations of the short-range ordered D2O molecules. No
firm evidence for the magnetic fluctuations has been found for the
NaxCoO2.yD2O, while the very weak intensity modulation observed in the j scans
along (1/2, 1/2, j) suggests the existence of the antiferromagnetic
fluctuations in the non-deuterated parts of the sample, the volume fraction of
which is estimated to be about 26 %. The present results indicate that magnetic
fluctuations, especially ferromagnetic ones are rather weak, in the deuterated
system, which is consistent with the results of the NMR Knight shift reported
by the present authors' group. We discuss the short-range ordered state of D2O,
too by analyzing the observed diffuse scattering.
