Abstract
High purity Fe16N2 was obtained by nitridation of α-Fe fine powder with ammonia at 120°C for various duration up to 100 hours. Crystallite size of Fe16N2 fine powder became smaller with the nitridation duration. Its coercivity showed a maximum of 2 kOe at the crystallite size of 22 nm. Saturation magnetization decreased with a reduction of the crystallite size and the value at 4.2 K was 154 emu/g. Sputter deposited α-Fe thin film was directly nitrided without an exposure to ambient air. Any kinds of iron nitride was not formed below 200°C on the films thicker than 360 nm. A mixture of Fe2-3N, Fe3N and Fe4N was obtained at 250°C. This nitride formation temperature was reduced with the film thickness. A small amount of Fe3N was observed in the α-Fe film nitrided at 130°C with a thickness of 50 nm.
