Perpendicular anisotropy induced in Fe-Ni amorphous ribbons containing phosphorus

A study is made with respect to an origin of the unusual anisotropy induced perpendicularly to the ribbon surface in Fe-Ni amorphous ribbons containing phosphorus by non-field annealing in H2or N2atmosphere. This anisotropy has a considerable dependence on iron content similar to the induced anisotropy observed in the case of field annealing. A formation of the oxidizing layer of a 4000 Å thickness is confirmed on the surface of ribbons in which the unusual anisotropy is induced. On the basis of domain model, it is shown that the layer is too thin to produce the stress-induced anisotropy for ribbons about 40 μm thick. The iron-content dependence of Ku´, which is a temperature invariant expression of Ku, indicates that the main cause of the perpendicular anisotropy is atomic directional ordering formed during process of the uniaxial diffusion of the iron atoms.