COMPETITION BETWEEN THE INTER-CHAIN INTERACTION AND SINGLE-ION-ANISOTROPY IN CONB2O6

A neutron scattering study of CoNb2O6, a quasi-one-dimensional (quasi 1D) ferromagnetic system with competition between the inter-chain inte raction and single-ion anisotropy, has been performed down to T simila r to 1.5 K. With decreasing temperature, in the 3D helical magnetic or dered phase below T-1 similar to 3.0 K, anomalous broadening of the ma gnetic Bragg peak reflecting such competition was observed. Furthermor e, in the antiferromagnetic phase below T-2 similar to 1.9 K, CoNb2O6 exhibits a pronounced 2D character even in the 3D ordered state.