Isothermal annealing behavior of zero-magnetostrictive permalloy films I theoretical

A simple theory is presented for the anisotropy relaxation during the course of isothermal magnetic annealing. An essential assumption of this theory is in the concept of elementary region (e-region): when the film is divided into the non-overlapping e-regions, the anisotropy in each e-region can or can not be relaxed by magnetic annealing at lower temperature depending on whether the e-region contains the excess vacancy or not. The extent of the e-region is determined by the net volume in which one excess vacancy wanders before its annihilation. Important results of this theory are as follows: the isothermal annealing behavior is divided into two stages even if the anisotropy is originated only from Fe-pair ordering. The relaxation frequency of both stages and the final saturation value of the anisotropy are hardly influenced by the pre-annealing (stabilization) of the film, while the fraction of the anisotropy affected by the first (or faster) stage depends on the stabilization, namely the more complete the stabilization is made, the smaller fraction of the first stage anisotropy results.