Magnetic properties of the ammonolysis product of α-Fe powder containing a small amount of aluminum

• Magnetic coercivity decreased in α”-Fe16N2 like compound as a soft magnet.
• Small amount of Al addition was effective in its preparation.
• Magnetic interaction decreased between the “α”-Fe16N2” particles.

Magnetite was prepared containing a small amount of aluminum and its nitride was generated through low temperature ammonolysis following reduction under hydrogen. The nitrided product was determined by XRD to be a mixture of “α″-Fe16N2” having a slightly deformed crystal structure from α″-Fe16N2 and the residual α-Fe. Magnetic coercivity of the mixture was decreased from the value of 150 mT obtained for the nitride product made without aluminum, due to the precipitation of nonmagnetic amorphous alumina in the low temperature nitrided bcc (Fe1−xAlx) with x≤0.03. The aluminum-doped nitride product in which the “α″-Fe16N2” fraction was 30 at% exhibited magnetization at 1.5 T of approximately 200 Am2kg−1 at room temperature and its magnetic coercivity was 20 mT.

Magnetic iron nitride particles were separated by nonmagnetic amorphous γ-alumina. Magnetic coercivity was decreased by reducing the magnetic interaction between the particles. Figure optionsDownload as PowerPoint slide