Formation of oxygen impurity faults during magnetic annealing of cobalt-rich amorphous alloys

Magnetic annealing effects such as field induced anisotropy and re-entrant magnetization behavior in cobalt-rich amorphous alloys appear to have their origin in structural inhomogeneities produced by internal segregation of oxygen atoms on cobalt 111 lattice planes. Electron diffraction demonstrated that these segregated oxygen atoms form planar oxygen impurity faults in the cobalt lattice normal to 〈111〉 directions. These faults interrupt the long-range ordering of cobalt atoms and lead to the altered cobalt lattice structure. A pair ordering of cobalt atoms may arise from oxygen impurity faults due to breaking of the cubic symmetry. A strong response to magnetic field annealing and the best re-entrant magnetic flux reversal were observed when the annealed ribbon surface consisted of cobalt grains with a high density of oxygen impurity faults.