Structural and magnetic properties of Fe[Fe(CN){sub 6}]{center_dot}4H{sub 2}O

We report the structural and magnetic properties of polycrystalline ferriferricyanide, Fe[Fe(CN){sub 6}]{center_dot}4H{sub 2}O. The room temperature neutron diffraction pattern of the sample was refined with space group Fm3m by the Rietveld refinement technique. The Moessbauer spectrum of the sample at room temperature reveals the presence of low spin Fe{sup 3+} (Fe{sup LS}, S=1/2) and high spin Fe{sup 3+} (Fe{sup HS}, S=5/2) ions. The compound undergoes a paramagnetic to ferromagnetic phase transition at 17.4 K. Saturation magnetization at 2.3 K corresponds to parallel ordering of Fe{sup HS} and Fe{sup LS} spin only moments in Fe[Fe(CN){sub 6}]{center_dot}4H{sub 2}O. Neutron diffraction study at 1.5 K shows the ordered site moments of 5.0(2) and 0.8(2) {mu}{sub B} for Fe{sup HS} and Fe{sup LS} ions, respectively, in Fe{sup HS}[Fe{sup LS}(CN){sub 6}]{center_dot}4H{sub 2}O. The coercive field of the compound is an order of magnitude higher than that of many other compounds in the Prussian Blue analog family. The observed branching between field-cooled and zero field-cooled magnetization below T{sub C} (=17.4 K) is ascribed due to magnetic domain kinetics under different cooling conditions and the presence of available vacant sites in the lattice for the water molecules.