SYNTHESIS, STRUCTURAL STUDY, AND MAGNETIC-BEHAVIOR OF A NEW CHLOROFLUORIDE FAMILY - BA(2)M(2)F(7)CL AND BA(2)MM'F7CL (M, M'=MN2+, FE2+, CO2+, NI2+, ZN2+)

A new chlorofluoride series, Ba(2)M(2)F(7)Cl and Ba(2)MM'F7Cl (M(2+), M'(2+) = Mn2+, Fe2+, CO2+, Ni2+, Zn2+), has been discovered. Structure determinations were achieved in the monoclinic P2(1)/m space group (Z = 2) for two single crystals with the following cell parameters: (1) Ba2Zn2F7Cl (a = 7.700(2) Angstrom, b = 5.801(2) Angstrom, c = 8.939(2) Angstrom, beta = 106.85(2)degrees) and (2) Ba2Co2F7Cl (a = 7.692(3) Angstrom, b = 5.783(2) Angstrom, c = 8.945(2) Angstrom, beta = 106.88(2)degrees). The reliability factors are respectively R((1)) = 0.028, R(w)(1) = 0.032 (for 795 structure factors and 65 refined parameters) and R(1(2)) = 0.036, wR(2(2)) = 0.044 (for 1065 structure factors and 64 refined parameters). The structure is built up from (MF(5)Cl) octahedra, sharing vertices in order to form puckered [MX(4)] layers. A cationic order is possible for the the Ba2MnNiF7Cl compound. The structure is compared to the BaZnF4 and NaCrF4 structure types. The magnetic measurements on the full series exhibit an antiferromagnetic behavior (except for the Zn family), as usually encountered in two-dimensional structures. (C) 1995 Academic Press, Inc.