Single crystal structures and magnetic properties of two iron or manganese-lead-antimony sulfides:: MPb4Sb6S14 (M: Fe, Mn)

Pure manganese benavidesite (MnPb4Sb6S14) has been synthesized from a solid state reaction of MnS, PbS and Sb2S3 at 600degreesC, and its crystal structure determined. Benavidesite is isotypic of natural jamesonite (FePb4Sb6S14), for which a new structure refinement was performed. Both compounds crystallize in the monoclinic symmetry, space group P2(1)/c (No. 14), with unit cell parameters (jamesonite/benavidesite) a = 4.0235/4.0216, b = 19.074/19.178, c = 15.737/15.837 Angstrom and beta = 91.89/91.89degrees, Z = 2. The projection of the structure along a shows rods (Pb4Sb6S14)(infinity) parallel to a, connected along c by iron/manganese atoms with octahedral coordination. Octahedra are connected by two opposite edges, forming single chains parallel to a. Magnetic properties have been studied. Jamesonite susceptibility shows an antiferromagnetic behavior below 30 K with an irregularity at about 5 K. Above 30 K, benavidesite and jamesonite have the same behavior but, at low temperature, benavidesite exhibits a paramagnetic behavior. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.