Two isotypic diphosphates LiM2H3(P2O7)2 (M=Ni, Co) containing ferromagnetic zigzag MO6 chains

Two new isotypic phosphates LiNi2H3(P2O7)2 (1) and LiCo2H3(P2O7)2 (2) have been hydrothermally synthesized and structurally characterized by the single-crystal X-ray diffraction technique. They crystallize in the monoclinic space group C2/c with the lattice: a=10.925(2) Å, b=12.774(3) Å, c=8.8833(18) Å, β=123.20(3)° for 1 and a=10.999(2) Å, b=12.863(3) Å, c=8.9419(18) Å, β=123.00(3)° for 2. The transition metal atoms are octahedrally coordinated, whereas the lithium and phosphorus atoms are all tetrahedrally coordinated. As the lithium-induced derivatives of MH2P2O7 (M=Ni, Co), 1 and 2 possess the same structure with MH2P2O7 in terms of topology, comprising the MO6 zigzag chains and P2O7 as the interchain groups. The magnetisms of 1 and 2 could be interpreted by adopting a quasi-one-dimensional (1D) zigzag chain model as that in their parent compounds: both 1 and 2 have ferromagnetic (FM) NiO6/CoO6 chains; 1 shows a FM cluster glass behavior at low temperatures, which is originated from the possible antiferromagnetic (AFM) next-nearest-neighbour intrachain interactions; 2 shows a AFM ordering at TN=2.6 K and a metamagnetic transition at HC=4.2 kOe at 1.8 K.

Graphical abstractLiNi2H3(P2O7)2 (1) and LiCo2H3(P2O7)2 (2) have been hydrothermally synthesized and structurally characterized. The MO6 octahedra share edges forming zigzag chains with P2O7 as the interchain groups. Both of them are quasi-one-dimensional magnets and have ferromagnetic MO6 chains; 1 is a ferromagnet, whereas 2 is a metamagnet.Figure optionsDownload full-size imageDownload as PowerPoint slide