MOMENT CANTING IN 3D-BASED AMORPHOUS FERROMAGNETS

The available evidence both for and against the existence of non-collinear spin structures in 3d-based amorphous ferromagnets is assessed, and supplemented with the results of an extended Fe-57 Mossbauer study of two series of post-production treated materials. Mossbauer spectra of as-received, stress-relieved and field-annealed ribbons of Fe78B13Si9 and Fe40Ni40B20 were recorded in zero applied field at room temperature for a number of angles of inclination between the gamma-ray beam and the normal to the ribbon plane. The resultant data were compared with four different moment distribution models: (i) a single uniform moment, (ii) an ellipsoidal distribution, (iii) a wedge-shaped distribution, and (iv) a two-moment domain model. None of these models provided an adequate description of the non-annealed ribbons, whereas model (iii) fitted the annealed Fe78B13Si9 ribbons and model (iv) fitted the annealed Fe40Ni40B20 ribbons. It is concluded that there is cumulative evidence in favour of ambient non-collinear spin structures in some annealed as well as non-annealed metallic glasses, but that the scale of the moment correlation lengths remains unresolved.