Ultrafine magnetic cyanide particles

Abstract

Cobalt- and nickel-iron hexacyanide powders were synthesized by the microemulsion method using CoCl2 or NiCl2 and K3FeIII (CN)6. The resultant powders K0.2Co1.4[Fe(CN)6].6.5H2O and K0.8Ni1.1[Fe(CN)6].4.5H2O were single phase with a mean particle size in the range of 5-10 nm. Curie temperatures 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. Superparamagnetic behavior was observed in the microemulsion-derived Ni-Fe cyanide particles. It has been found that a heat treatment at 150°C led to a presence of a soft magnetic phase and a strong reduction of magnetic anisotropy. © 2000 American Institute of Physics.