Magnetic interactions in Fe 1− x M x Sb 2 O 4 , M = Mg, Co, deduced from Mössbauer spectroscopy

Magnesium- and cobalt- substituted FeSb 2 O 4 , of composition Fe 1− x Mg x Sb 2 O 4 (x = 0.25, 0.50, 0.75) and Fe 0.25 Co 0.75 Sb 2 O 4 have been examined by 57 Fe Mössbauer spectroscopy. The complex spectra recorded from the magnetically ordered materials are interpreted in terms of models in which the dominant magnetic interactions occur along the rutile-related chains of FeO 6 octahedra in the magnetic structure of FeSb 2 O 4 . In materials of the type Fe 1− x Mg x Sb 2 O 4 , the diamagnetic Mg 2+ 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 Mg 2+ ions. In Fe 0.25 Co 0.75 Sb 2 O 4 the spectra are composed of components from different configurations of neighbouring Fe 2+ and Co 2+ ions.