The Mössbauer Study of the Ferrous Ion in Some Anhydrous Dihalides of Iron-Group Elements

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The Mössbauer measurements on the ferrous ion in FeBr₂, CoCl₂ and NiCl₂ are presented. Various interaction parameters are estimated from the observed spectra. The effect of anion change on the ferrous ion is discussed, comparing the results on FeBr₂ with those on FeCl₂ and FeI₂ reported previously. The spectra observed below the Néel temperature show that the ferrous spin in CoCl₂ is forced to lie in the c plane, whereas that in NiCl₂ orients along the c axis which is the direction preferred by the ferrous spin. These can be interpreted in terms of the difference in anisotropy energy of the host spins.