Structure refinement, EPR, Specific magnetic heat and magnetic properties of ZnMnP2O7 diphosphate

The structure of the diphosphate ZnMnP2O7 is determined on powder by the Rietveld method. It is of monoclinic symmetry C2/m. The cell parameters are: a = 6.6141(3) angstrom, b = 8.4366 (3) angstrom, c = 4.5305(2) angstrom and beta = 103.948(2)degrees. The structural framework is built by MO6 octahedron planes where M is a mixed site statistically occupied by Zn2+ and Mn2+ ions. These planes are parallel to the crystallographic plane (001) and are linked together by sheets of P2O74- groups. The value of the paramagnetic temperature Theta p is -4 K, which proves that the interactions are antiferromagnetic. The magnetic specific heat of this compound has a symmetric maximum at T = 5.3 K less acute compared to that of Mn2P2O7 of isotypic structure which is of lambda type. This behavior change can be explained by the interruption of the three-dimensional interactions between Mn2+ ions which become limited to 2D order when 50% of these ions are replaced by Zn2+ ions.