Magnetic interaction in ferrous antimonite, FeSb2O4, and some derivatives

Ferrous antimonite, FeSb2O4, which is isostructural with Pb3O4, and some lead- and cobalt-doped variants of composition FeSb1.5Pb0.5O4 and Co0.5Fe0.5Sb1.5Pb0.5O4 have been examined by 57Fe and 121Sb Mössbauer spectroscopy. Antimony is present as Sb3+. The presence of Pb2+ on the antimony site induces partial oxidation of Fe2+ to Fe3+. There is no Verwey-type transition in which electrons are shared between iron in different oxidation states. The quasi-one-dimensional magnetic structure gives rise to situations in which weakly coupled Fe2+ ions can coexist in a non-magnetic state alongside Fe3+ ions in a magnetically ordered state.