Crystal Structure and Magnetic Properties of Li2Mn2(SO4)3

The crystal structure of dilithium dimanganese trisulfate Li2Mn2(SO4)3 has been established by single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic system (space group Pbca, Z=8) with cell parameters a=8.686(2) ?, b= 8.792(2) ?, and c=24.146(4) ?. The structure was refined to R=0.035 and Rw=0.037 using 2622 independent reflections. Lithium and sulfur atoms are in most regular tetrahedral oxygen coordination, manganese atoms are in slightly distorted octahedral oxygen coordination. Formally, the 3-D framework can be described, starting from the Li2Mg2(SO4)3 structure, by condensation of Sc2(WO4)3-type slabs. As a result, half of the LiO4 and MnO6 polyhedra share an edge, forming Li2O6 and Mn2O10 dimeric entities. Below TN=10 K, the magnetic susceptibility evolution is characteristic of a long-range antiferromagnetic order. In the high-temperature region, the susceptibility follows a Curie–Weiss law with C=8.51 cm3 K mol-1 and =-19 K. In a Mn2O10 bioctahedron the Mn2+ cations are indeed antiferromagnetically coupled with an interaction parameter J=-6.5 cm-1.