A Study on Magnetic Properties of Fe4N Powders

Magnetization and Mössbauer spectra were measured for three kinds of Fe4N powders made from acicular ¿-FeOOH, ¿-Fe2O3 and carbonyl iron powders. Except for the Fe4N powder from carbonyl iron, the saturation magnetization was lower than the bulk value (190 emu/g). A large amount of oxygen and small amounts of Ni, Zn and Si were detected in the sample obtained from ¿-FeOOH. From the Mössbauer spectra, it was concluded that decreases in the saturation magnetization were mainly due to the coexistence of a paramagnetic phase. A large quadrupole splitting of the paramagnetic peak indicates that the paramagnetic phase may be an oxide consisting of Fe(II) ions, e.g. wustite. In addition, it is thought that Ni and Zn preferentially substitute for Fe at the corner sites of fcc Fe4N, and also reduce the magnetization.