On the Origin of M‐Induced Anisotropy in Nickel and Permalloy Films

The anisotropy field strength H K is measured in thin nickel and 81/19 nickel‐iron films immediately after deposition and during subsequent systematic annealing in external magnetic fields. These measurements are performed with the films kept in ultra high vacuum using a planar Hall effect method. An analysis of the H K ‐isotherms and of the temperature dependence of H K gives the spectrum of H K ‐contributions of a given film with their relaxation times and activation energies. In non‐magnetostrictive permalloy the main contribution to the anisotropy (of 60 to 85%) is attributed to directional ordering of the iron pairs. In nickel a complicated concurrence of several anisotropy contributions is found. The contribution of the magnetoelastic energy dominates; it can be understood in terms of the constraint model.