SYNTHESIS PROCESS AND GIANT MAGNETIZATION OF INTERSTITIAL TYPE (Fe、Co)-(B、C、N) SINGLE CRYSTALS

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We investigated possibility of existence of Fe16N2 superstructure (alpha" phase)、which has been claimed to have a giant magnetization (3.0 Tesla) but have been controversial、and other thinkable superstructures in (Fe、Co)-(B、C、N) system. We found that in the latter system B、C、N atoms are included in Fe、Co interstitially. Fe tends to form a martensite phase by this inclusion resulting in an increase of magnetization. However、no evidence of superstructure was obtained for this system. Through investigation of the martensite phase of Fe-N and its superstructure by developing high precision method of X-ray analysis、magnetization measurement and sample synthesis、the following results were obtained.1) We clarified by high precision determination of the rate of the superstructure included in the martensite that its magnetization takes any value in a range of 2.4-3.0 Tesla depending sensitively on deformation of the lattice. All data reported up to date by many research group which conflict with each other can be explained consistency in terms of the lattice deformation. 2) Further investigation of formation process、thermal stability and resultant lattice deformation of alpha" led us to the conclusion that it is highly possible that the giant magnetization is a result of the deformation from bcc to fcc like structure and the large variety of magnetization associated with alpha" is from 「the high and low spin state」 which has been found in the fcc Fe.Finally we conclude that the giant magnetization is in existence and it is stabilized by an anisotropic stress imposed on the lattice during formation of the superstructure and we could put an end to one of the largest controversy which lasted for these 25 years.