Structure and magnetic properties of copper(II) hexacyanoferrate(III) compound

Molecular magnet copper(II) hexacyanoferrate(III) powder, Cu-1.5[Fe(CN)(6)]. 6H(2)O was prepared by coprecipitation method where the particle size is in the nanoscale range. It possessed a face-centered cubic (FCC) crystal structure with lattice parameter of around 10 Angstrom. This ferromagnetic powder has a Curie temperature of 19 K. The effects of annealing on its physical as well as magnetic properties were studied. The Fe-III-CN-Cu-II structure is the major structure in the freeze-dried Fe-Cu cyanide. As the cyanide was annealed at higher temperature, two other structures appeared, namely Fe-II-CN-Cu-III and Cu-II-CN-Fe-III as probed by Fourier-transform infrared (FTIR) and Mossbauer techniques. After annealing at 140 degreesC, Fe-III-CN-Cu-II structure disappeared while Fe-II-CN-Cu-III structure appeared to be the dominant structure. Complete decomposition of the cyanide phase occurred at around 370 degreesC, whereby nanoscale Fe-Cu particles were found, as well as significant amount of amorphous carbon particles. These soft magnetic Fe-Cu particles have M-s value of 32 emu/g and coercivity of 0.5 kOe. (C) 2001 Published by Elsevier Science Ltd.