Amorphous Co75.26-xFe4.74(BSi)20+x magnetic alloys were examined, using transmission electron microscopy, after magnetic field annealing. Transmission electron microscopic analysis revealed that the crystallized Co layer under a surface oxide could be highly faulted, with planar defects, depending upon the composition. On the basis of the electron diffraction data, a new form of stacking fault was proposed in which two O atoms were substituted for face-centered cubic Co in the {111} planes so as to create randomly distributed clusters of O atoms on the Co {111} planes. Such clusters could explain the absent {200} peak in the highly faulted composition of crystallized face-centered cubic Co, and the streaks observed in the electron diffraction pattern of the material. The O fault was also closely related to the magnitude of the induced magnetic anisotropy of the material; thus suggesting that the Co–O bonds acted as a localized antiferromagnetic region.

Oxygen Condensation Stacking Faults in Crystallized Co Found during Magnetic Annealing of Co-Rich Amorphous Alloy. H.Kyung, C.S.Yoon, C.K.Kim: Journal of Materials Science, 2002, 37[10], 1967-72