Ultrafine cobalt-iron cyanide particles prepared by microemulsion method

Cobalt-iron cyanide particles having ferromagnetic behavior with a Curie te mperature T-C of 14 to 15 K can be precipitated by mixing (CoCl2)-Cl-II and K3FeIII(CN)(6). This similar reaction was carried out in the water pools o f reverse micelles. By using nonionic surfactant poly(oxyethylene)(5) nonyl phenol ether (NP5) and poly(oxyethylene)(9) nonyl phenol ether (NP9) and p etroleum ether (PE), reverse micelles can be made with a water pool of spec ific size which can be usually varied by the water/surfactant ratio. Such c ombination of surfactant, oil and aqueous solution provides a unique reacto r environment for the synthesis of molecular-based magnetic particles of na rrow size distribution. Molecular-magnetic powders, K0.28Co1.29[Fe(CN)(6)] . 6.5 H2O with particle size ranging from 5 to 10 nm have been successfully synthesized by the water-in-oil microemulsion technique. These particles h ave a Curie temperature of approximate to 14 K as determined using the Curi e-Weiss law. High coercivity of 1.8 kOe was also measured for the ultrafine powder at 4.2 K. Structural and magnetic properties of the resulting magne tic materials are reported. This work has shown that microemulsion can be a powerful process to synthesize ultrafine molecular magnet particles exhibi ting high coercivity.