Magnetic properties of multi-metal Prussian Blue analogue Co0.75Ni0.75[Fe(CN)6]·6.8H2O

We have studied magnetic properties of the ternary metal Prussian Blue analogue Co0.75Ni0.75[Fe(CN)6]·6.8H2O. Room temperature Mössbauer and IR spectra give the evidence of two FeIII sites in the compound. It undergoes a paramagnetic to ferromagnetic phase transition at 15.9 K. Field dependent magnetization data correspond to a ferromagnetic ordering of the spin only moments of FeIII, CoII and NiII ions. Approximately 87.45% FeIII ions are in low spin (S=12) and 12.55% FeIII ions are in high spin (S=52) state. On the other hand, 100% CoII ions are in low spin (S=12) and 100% NiII ions are in (t2g)6(eg)2 spin state (S=1). The observed very large coercive field at lower temperatures is an indication of the presence of magnetic hardness in the compound. Non-saturation of magnetization at 1.5 K even under 100 kOe field and a bifurcation in the field cooled and zero field cooled magnetization curves indicate the presence of some spin glass type component in the compound.