Cu-NMR Study on the Quasi one Dimensional Antiferromagnet Cu3Mo2O9

Quasi one dimensional antiferromagnet Cu3Mo2O9 consists of spin chains and inequivalent spin pairs clinging on them, and shows the magnetic order at TN = 7.9K. The local structure of tetrahedron formed by neighboring four spins suggests a non-collinear spin structure in the ordered state and hence the multiferroicity. We have performed Cu-NMR measurements at low temperatures below TN and showed that the observed spectra are consistent with the report by the recent neutron elastic scattering experiments in that the chain site Cu has only an extremely small ordered moment.