Electrochromism and electrochemical magnetism in Ni–Fe Prussian blue

We studied the electrochemical and magnetic properties of NiFe Prussian blue. The NiFe Prussian blue was synthesized on Ni electrodes in the form of thin films by an electrochemical technique. Measurements of its magnetic properties show that NiFe Prussian blue with the Fe^{III-low spin (LS)}–CN–Ni^II structure exhibits ferromagnetic properties, with T _c (critical temperature)=25 K. On the other hand, the reduced form, which has the Fe^II-LS–CN–Ni^II structure, is paramagnetic. This means that the magnetic properties can be controlled between ferromagnetic and paramagnetic by an electrochemical method. Furthermore, it is well known that NiFe Prussian blue exhibits electrochromic properties. Hence, this compound is a multifunctional, molecule-based compound in which optical and magnetic properties can be controlled by an electrochemical redox reaction. Contribution to the special issue on “Magnetic field effects in Electrochemistry.”