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

The Mössbauer measurements on the ferrous ion in FeBr 2 , CoCl 2 and NiCl 2 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 FeBr 2 with those on FeCl 2 and FeI 2 reported previously. The spectra observed below the Néel temperature show that the ferrous spin in CoCl 2 is forced to lie in the c plane, whereas that in NiCl 2 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.