Incommensurate antiferromagnetic order in the S=1/2 quantum chain compound LiCuVO4

The linear spin chain (S = 1/2) compound LiCuVO4 was investigated by elastic neutron diffraction, susceptibility and heat-capacity measurements on single crystals. Long-range incommensurate magnetic ordering with a propagation vector k = (0,0.532,0) is observed below 2.1(1)K by elastic neutron diffraction. The refinement of the magnetic structure indicates that the Cu2+ moments lie within the ab-plane, to enclose an angle of similar to 90 degrees to each other along the chain, and have a magnitude of 0.31(1)mu(B). These findings are attributed to the competition of nearest-and next-nearest-neighbour exchange coupling in the edge-sharing CuO2 chains. (C) 2004 Elsevier B.V. All rights reserved.