Ultrafine magnetic cyanide particles

Cobalt- and nickel-iron hexacyanide powders were synthesized by the microem ulsion method using CoCl2 or NiCl2 and K3FeIII (CN)(6). The resultant powde rs K0.2Co1.4[Fe(CN)(6)].6.5H(2)O and K0.8Ni1.1[Fe(CN)(6)].4.5H(2)O were sin gle phase with a mean particle size in the range of 5-10 nm. Curie temperat ures of the cobalt- and nickel-iron cyanide powders were estimated to be 14 and 28 K, respectively, using Curie-Weiss law. The coercivity was measured to be 1.8 kOe for nanoscaled Co-Fe cyanide particles. High coercivity of 4 .0 kOe was achieved in the coprecipitated Ni-Fe cyanide powder. Superparama gnetic behavior was observed in the microemulsion-derived Ni-Fe cyanide par ticles. It has been found that a heat treatment at 150 degrees C led to a p resence of a soft magnetic phase and a strong reduction of magnetic anisotr opy. (C) 2000 American Institute of Physics. [S0021-8979(00)18508-1].