Sequential Assembly of Homogeneous Magnetic Prussian Blue Films on Templated Surfaces

Thin homogeneous films of the Prussian blue analogues with idealized formulas KFeIII-[Fe^II(CN)₆], KNi^II[Fe^III(CN)₆], CsNi^II[Cr^III(CN)₆], and KCr^II[Cr^III(CN)₆] have been prepared through the sequential adsorption of the appropriate metal ions and hexacyanometalate complexes onto hydrophobic surfaces that were first templated with an Fe-CN-Ni twodimensional grid network deposited as a Langmuir-Blodgett monolayer. The template is essentially one layer of the cubic Prussian blue structure and provides a well-matched surface for the deposition of the bulk cubic solids. The effectiveness of the method is verified by the exceptional surface coverage indicated by atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies. Grazing incidence X-ray diffraction (GIXD) using synchrotron radiation confirms the face-centered cubic structures of the product films. Magnetic measurements of the thin films prepared on Mylar substrates yield behavior similar to that observed in the analogous powders, with the KFeIII-[Fe^II(CN)₆], KNi^II[Fe^III(CN)₆], and CsNi^II[Cr^III(CN)₆] films ordering ferromagnetically with T_c = 5, 20, and 75 K, respectively. The KCr^II[Cr^III(CN)₆] film orders ferrimagnetically at T_c = 210 K.