Hydrogen induced anisotropy in magnetic amorphous ribbons

A study about induced anisotropy by hydrogen charging has been performed in both, positive and negative magnetostrictive amorphous alloys. A strong perpendicular to surface anisotropy at the sample surface in every hydrogenated sample has been observed from Bitter pattern and from hysteresis loops obtained by magnetooptical Kerr effect. This perpendicular anisotropy is only in the volume fraction near to sample surface, as it is inferred from hysteresis loops and magnetization curves measured by induction. A model assuming that the large perpendicular induced anisotropy is due to the mechanical stresses produced by the change of volume of the hydrogenated zones has been developed. From this model, by fitting experimental results, anisotropy energy, internal stresses, and hydrogen charged volume have been calculated.