Magnetic, Structural and Spectroscopic Properties of Iron(II)-Octacyanoniobate(IV) Crystalline Film Obtained by Ion-Exchange Synthesis

Over recent years, investigations of coordination polymer thin films have been initiated due to their unique properties, which are expected to be strongly enhanced in the thin film form. In this work, a crystalline [Fe(II)(H(2)O)(2)](2)[Nb(IV)(CN)(8)]∙4H(2)O (1) film on a transparent Nafion membrane was obtained, for the first time, via ion-exchange synthesis. The proper film formation and its composition was confirmed with the use of energy dispersive X-ray spectroscopy and infrared spectroscopy, as well as in situ Ultraviolet-Visible (UV-Vis) spectroscopy. The obtained film were also characterized by scanning electron microscopy, X-ray diffraction, and magnetic measurements. The [Fe(II)(H(2)O)(2)](2)[Nb(IV)(CN)(8)]∙4H(2)O film shows a sharp phase transition to a long-range magnetically ordered state at T(c) = 40 K. The 1 film is a soft ferromagnet with the coercive field H(c) = 1.2 kOe. Compared to the bulk counterpart, a decrease in critical temperature and a significant increase in the coercive field were observed in the films indicating a distinct size effect. The decrease in T(c) could also have been related to the possible partial oxidation of Fe(II) ions to Fe(III), which could be efficient, due to the large surface of the thin film sample.