Magnetic interactions in Fe1-xMxSb2O4, M = Mg, Co, deduced from Mössbauer spectroscopy

Magnesium- and cobalt- substituted FeSb2O4, of composition Fe1−xMgxSb2O4 (x = 0.25, 0.50, 0.75) and Fe0.25Co0.75Sb2O4 have been examined by 57Fe Mössbauer spectroscopy. The complex spectra recorded from the magnetically ordered materials are interpreted in terms of two models in which the dominant magnetic interactions occur along the rutile-related chains of FeO6 octahedra in the magnetic structure of FeSb2O4. In materials of the type Fe1−xMgxSb2O4, the diamagnetic Mg2+ ions have no magnetic moment and behave as non-magnetic blocks which disrupt the magnetic interactions in the chains along the c-axis forming segments of iron-containing chains separated by Mg2+ ions. In Fe0.25Co0.75Sb2O4 the spectra are composed of components from different configurations of neighbouring Fe2+ and Co2+ ions.