Mössbauer Investigation of the Ferromagnetic Coupling in Copper-Iron Polycyanides

One of the Prussian blue analogs, molecular magnet Cu^II₃Fe^III(CN)₆₂.11.6H₂O, was investigated by Mössbauer spectroscopy. It was found that transition temperature was around T_C = 18.5 K from paramagnetic phase to ferromagnetic phase. The β value of the critical exponent is around 0.338 at magnetic ordering temperature. Therefore, the ferromagnetic coupling interaction of Cu-Fe cyanide could be clearly explained by spin wave theory.