Discovery of Fe16N2 with Giant Magnetic Moment and Its Future View

This paper recounts the discovery and identification of the giant magnetic moment of the compound Fe₁₆N₂, and focuses on several important points that the author heeded in experimental work leading up to the discovery. In particular, the paper emphasizes the importance and necessity of simple and natural ideas and considerations arising from experiments. In order to determine the true value of the M_s of Fe₁₆N₂, the following had to be accomplished: (1) the experimental error arising from measurements of the film thickness (volume) and magnetization had to be eliminated, and an appropriate magnetic resonance technique had to be adopted; (2) thermomagnetic analysis of film samples had to be performed to determine the coexistence of Fe₁₆N₂ and ^--Fe, enabling determination of the true Ms of Fe₁₆N₂ (2200 G, 2.9 μB/Fe atom); and (3) Mossbauer effect measurements had to be made to corroborate the Ms values obtained. Recent work on Fe-N (B, C...) alloys and on potential uses of Fe₁₆N₂ as a conventional magnetic material are reviewed.