Hyperfine interactions at 57Fe in Fe2+-doped MnCO3

Mössbauer spectroscopy has been used to determine the magnetic state of Fe²⁺ ions that have been substituted for Mn²⁺ in MnCO₃ for temperatures between 1.8 °K and the Néel temperature (~ 35 °K). Iron concentrations up to 10 mole% have been examined. Within these ranges, the ⁵⁷Fe Mössbauer spectra show marked dependence on both iron content and temperature. The results have been interpreted in terms of the interactions between the magnetic crystal and a single ferrous ion, and support a model proposed recently for this system in which the Mn²⁺ spins are reoriented in the presence of the ferrous ions due to their large single-ion anisotropy in the trigonal crystal field.