Influence of electron capture decay of ⁵⁷Co on the Mössbauer emission spectrum of hydrated cobalt chlorides

The Mössbauer emission spectra of ⁵⁷Co in CoCl₂ · 2H₂O and CoCl₂ · 6H₂O measured from 1.6 to 300 °K exhibit both the divalent and the trivalent charge states of ⁵⁷Fe associated with numerous defect configurations. A close comparison of these spectra with the absorption spectra of 0.1 at.% ⁵⁷Fe in the same hydrated cobalt chloride hosts is made. We demonstrate that the anomalous charge states and the defect species are a consequence of the self-radiolysis of the water ligands by the low energy electrons and x rays produced from the electron capture decay. The experiments in the antiferromagnetic state of these compounds suggest that the damage occuring from the self-radiolysis in the neighborhood of the decaying ion breaks the magnetic superexchange paths.