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Four chemically distinct iron voitaites of composition A 2 R 5 2+ Q 3 3+ Al(SO 4 ) 12 ∙18H 2 O where (A, R, Q) are respectively (K, Fe, Fe) (true voltaite), (K, Fe, In), (NH 4 , Mn, Fe), and (Tl, Cd, Fe) were prepared by Mereiter who had previously done an X-ray structure determination on this material. These samples were studied by the Mössbauer effect to determine the site preference of Fe 2+ and Fe 3+ between two nonequivalent octahedrally coordinated sites M(1) and M(2): Magnetization measurements show that the magnetic ions have their free spin moment and that ferrimagnetic ordering takes place below 1 K in the cases where (A, R, Q) in the formula are (K, Fe, Fe), (NH 4 , Mn, Fe), and possibly in the case (Tl, Cd, Fe). The material (K, Fe, In) is antiferromagnetic with θ = −3 K.
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Hermon et al. (1976) studied this question.