INDUCED SURFACE ANISOTROPY OF AMORPHOUS IRON-NICKEL ALLOYS STUDIED BYFERROMAGNETIC-RESONANCE AND ANTIRESONANCE

The thermally induced (by annealing) surface anisotropy (SA) is studie d in ribbon-shaped iron-rich amorphous alloys (prepared by roller quen ching method), mainly by the methods of ferromagnetic resonance and an tiresonance at frequencies in the range 9-95 GHz, in external static m agnetic fields oriented either in the plane of the ribbon or perpendic ularly to the plane. The large difference between the ferromagnetic re sonance and antiresonance penetration depths is pointed out. The magne tic homogeneity of the samples is checked. The induced surface anisotr opy constant K-s amounts to several tenths of erg/cm(2), its symmetry is uniaxial with the easy axis oriented along the normal to the sample surface. The temperature dependence of K-s reveals a critical point a round 400 K, above which K-s approximate to 0. The origin of SA lies m ost probably in occurrence of non-stoichiometric ferrimagnetic oxides, which arise in the annealing process in a few surface atomic planes o f the sample and which interact with the bulk of the material. The mag netoelastic origin of the interaction is not probable.