Magnetic properties of electrochemically prepared crystalline films of Prussian blue-based molecular magnets KjCrkII[CrIII(CN)6]l•mH2O

Crystalline films (thickness similar to 1 mu m) of Prussian blue-based molecular magnets, synthesized using electrochemical method at two different reduction potentials -0.5 and -0.9 V, result into K0.1Cr1.45II[Cr-III(CN)(6)]center dot mH(2)O (film 1) and K0.8Cr1.1II[Cr-III(CN)(6)]center dot mH(2)O (film 2), respectively. The structural and magnetic properties of such films are investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), infrared (IR) spectroscopy, and dc magnetization measurements. The film morphology, examined using AFM, shows uniformly distributed triangular crystallites over the substrate surface. The presence of Cr-III-C=N-Cr-II sequence, in the range of 1,900 to 2,300 cm(-1) in IR spectra, confirms formation of Prussian blue analogues. The XRD results reveal information about the crystalline nature of the films and the relative intensities of the Bragg peaks change with the K+ ions. The exchange interaction between Cr ions through C=N ligand confirms that the electron transfer from C N molecule to Cr ions is ferrimagnetic in nature. The high Curie temperatures (T-C) are found to be similar to 195 and similar to 215 K for film 1 and film 2, respectively. The higher value of T-C is attributed to the inclusion of more K+ ions for film 2, resulting decreases in the Cr-III(C=N)(6) vacancies and increases in the number of nearest neighbors of Cr-II ions. The branching in the zero field-cooled and field-cooled magnetization data below Curie temperature is explained in terms of kinetic behavior of magnetic domains with different cooling conditions and the presence of water molecule vacancies in the lattice.