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

Abstract

The mineral schafarzikite, FeSb₂O₄ (space groupP4₂/mbc), has been synthesised and antimony substituted by lead to form a series of compounds of formulation FeSb_2−xPb_xO₄ (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.