MAGNETIC-BEHAVIOR OF THE PBXM3F12-CENTER-DOT-3H(2)O PHASES (M=MN2- NONCOLLINEAR ANTIFERROMAGNETISM(, FE2+, FE3+) )

Structural and magnetic studies of the PbxM3F12. 3H(2)O phases (M = Mn 2+, Fe2+ and Fe3+) have been made. The presence of iron in these fluor ides showing columnar structures allowed a complete investigation usin g Mossbauer experiments without and with magnetic field. The values of hyperfine field at iron sites indicate an appreciable zero-point spin reduction. High-field Mossbauer spectrometry and neutron diffraction evidence, on the other hand, a noncollinear magnetic structure that ca n be attributed to the existence of magnetic topological frustration. This frustration is the consequence of antiferromagnetic interactions within the cationic triangular units of the crystal structure. Also, t he lowering of hyperfine field at iron sites is consistent with the 1D magnetic character of the isolated triple chains of octahedra charact eristic of these compounds in addition to the magnetic frustration imp lied by the cationic topology.