CRYSTAL-STRUCTURE OF BA6MN2ZNF12CL6

The new Ba6Mn2ZnF12Cl6 phase has an hexagonal symmetry (space group P6(3)/m) with a=10.081(1)angstrom c=5.8476(1)angstrom and Z=1. The structure has been refined from 1046 reflections down to R=0.0221, wR=0.0227. It can be described as built up from isolated [ZnCl6]n and [MnF6]n chains parallel to c-axis which are separated from each other by the barium cations in ten-fold coordination. The [ZnCl6]n chains are formed by face sharing octahedra similar to those of the 2H hexagonal perovskite but zinc occupies in a disordered way only one half of the sites. Manganese is located in a fluorine triangular prism (D3h symmetry) which is an unusual environment for this cation. The prisms are associated by face sharing along the c-axis with an 1-1 ordering between occupied and vacant sites. As a consequence manganese atoms are isolated in the chains. This result has been confirmed by magnetic susceptibility measurements, Ba6Mn2ZnF12Cl6 following a Curie law down to 4.2K.