The synthesis, structure, magnetic and electrical properties of FeSb2-xPbxO4

The mineral schafarzikite, FeSb2O4 (space group P4(2)/mbc), has been synthesised and antimony substituted by lead to form a series of compounds of formulation FeSb2-xPbxO4 (x = 0.2-0.7). The replacement of Sb3+ by Pb2+ induces oxidation of Fe2+ to Fe3+ with a concomitant decrease in the a- and increase in the c-lattice parameter. SQUID magnetometry and neutron powder diffraction show that FeSb2O4 orders antiferromagnetically at 45 K and has a predominately A-type magnetic structure in which the moments are aligned parallel within the layers and antiparallel within the chains directed along the c-axis. The presence of a G-type component is also indicated in the neutron diffraction pattern with no evidence of an additional C-type component. The lead-doped variants exhibit magnetic ordering at ca. 50-70 K to a canted antiferromagnetic state with a C-type magnetic structure in which the moments are arranged ferrromagnetically within the chains and antiferromagnetically within the layers.