Ferromagnetism of the Me₃(Fe(CN)₆)₂.H₂O compounds, where Me=Ni and Co

Abstract

We have studied the structural and magnetic properties of two compounds from the Me32+(Fe3+(CN)6-)23-.H2O family, where Me=Ni and Co. From x-ray analysis we find that the compounds crystallize in the face-centred cubic structure with the space group of F43m. Both the Fe and Me ions are coordinated octahedrally by six carbon atoms and six nitrogen atoms, respectively. The Fe ions are in a strong crystalline field, while the Me ions are in an intermediate field with cubic symmetry. From the magnetic studies a quantitative bulk ferromagnetic behaviour (a spontaneous magnetization and a hysteresis loop) has been established for both complex compounds. In addition, from the magnetization against temperature curves we obtained, for both compounds, the Curie as well as Curie-Weiss temperatures, the Curie constants and the effective moments in the paramagnetic state. From the assumed value of the spin for every cation we fitted the chi T=F(T) curves and from the field dependence of the magnetization we determined the high-field susceptibility. The magnetic properties of the compounds were analysed in the framework of the mean-field theory.