Reinterpretation of Data on Multiple Charge States of Fe in CoO

It is suggested that the samples studied in recent Mössbauer experiments on CoO doped with ⁵⁷Co included microcrystals as well as polycrystalline bulk. This interpretation resolves the conflict concerning the temperature reversibility of the interconversion between the observed ferrous and ferric valence states, and is consistent with the cation-vacancy stabilization model.