Magnetic structure and properties of Pb8FeIIFe2IIIF24:: a 1-D chain compound exhibiting a spin-flop transition

The magnetic structure of (Pb8FeFe2F24)-Fe-II-F-III was solved starting from its neutron diffraction powder pattern obtained at 1.4 K and its magnetic properties were characterized using the data recorded on a SQUID magnetometer and on a magneto-susceptometer. (Pb8FeFe2F24)-Fe-II-F-III is triclinic; space group P (1) over bar; its crystal structure was previously solved on a single crystal. The magnetic structure of this fluoride is built up from ferimagnetic chains antiferrommagnetically coupled approximately along the c-axis of the cell, making up layers parallel to the (b,c) plane. Two successive layers exhibit different orientations of the magnetic moments. The net magnetic moment of (Pb8FeFe2F24)-Fe-II-F-III is equal to zero in agreement with an antiferromagnetic structure. This magnetic structure does not evolve in the temperature range: 1.4-20 K. Thus, only one magnetic phase occurs below T < T-N approximate to 21 K. Under a sufficiently strong magnetic field (H > 5000 Oe), (Pb8FeFe2F24)-Fe-II-F-III exhibits a spin-Flop transition. (C) 1999 Published by Elsevier Science S.A. All rights reserved.