A highly ordered two-dimensional hybrid magnetic nanocomposite has been prepared by synthesizing and intercalating a new cationic aluminum-hydroxy ferric ferrocyanide compound into a cation-adsorbing nanoclay (montmorillonite). Chemical and structural properties were investigated by X-ray diffraction, transmission electron microscopy, thermogravimetric and differential thermal analyses, Fourier transform infrared, X-ray photoemission, and Mossbauer spectroscopies. Elemental analysis was based on proton-induced gamma ray emission and X-ray fluorescence spectroscopy data, N/C elemental ratios, and cation-exchange capacity measurements. Magnetic properties were studied by SQUID magnetometry. The results suggest: (i) that the cationic Prussian blue analog comprises Al-hydroxy cations embedded into a monolayer thick two-dimensional ferric ferrocyanide array; and (ii) that the clay-Prussian blue nanohybrid consists of such arrays stacked between the clay layers. The latter material orders ferromagnetically at 5 K showing a hundred times higher remanence than that of the starting material, soluble Prussian blue (ammonium ferric ferrocyanide). (C) 2010 Elsevier Inc. All rights reserved.