Observation of the in-plane ordering of D2O molecules in NaxCoO2·yD2O by neutron diffraction

Abstract Neutron elastic and inelastic scattering studies on aligned crystals of NaxCoO2·yD2O containing the superconducting bilayer (y∼1.3) phase, and the non-superconducting monolayer (y∼0.6) and non-deuterated phases have been carried out. In the elastic scans along ( 1 / 2 , 1 / 2 , l), we have observed a significant diffuse scattering contribution. Analyzing the intensities of this diffuse scattering, we discussed the short-range ordered state of D2O in the bilayer phase. In the inelastic scattering, although we have observed phonon peaks from the vibration of D2O molecules, no firm evidence for the existence of the ferromagnetic fluctuations has been found in the crystal, while a very weak intensity modulation which suggests an antiferromagnetic fluctuation of non-deuterated phase has been observed.