Crystal Growth, Crystal Structure, and Magnetic Properties of a New Lithium Cobalt Diphosphate

Single crystals of the new lithium cobalt diphosphate Li 6 Co 5 (P 2 O 7 ) 4 have been grown, and their structure has been determined by X-ray diffraction techniques. This compound crystallizes in the triclinic space group P 1̄ with a = 6.3009(7), b = 8.413(1), and c = 9.937(1) Å, α = 107.894(2), β = 90.247(2), and γ = 92.782(2)°, V = 500.6(1) Å 3, and Z = 1. The structure of Li 6 Co 5 (P 2 O 7 ) 4 is characterized by the arrangement of CoO 6 octahedra, CoO 5 trigonal bipyramids, and diphosphate groups. The CoO 6 octahedra share edges forming infinite zigzag chains [Co 3 O 14 ] running along the b direction. Laterally, such chains share octahedra corners with CoO 5 trigonal bipyramids and P 2 O 7 diphosphate groups connecting with another symmetrically equivalent chain. The connection between these polyhedra defines tunnels along the [100], [001], and [011] directions, where the Li cations are located. The tunnel intersection gives rise to a three-dimensional channel system. Magnetic measurements reveal the presence of antiferromagnetic interactions in the Co 2+ sublattice at about 11 K. The field dependence of magnetization shows that this compound exhibits a metamagnetic transition.