ANNEALING BEHAVIOR OF INDUCED ANISTROPY AND RELATED MAGNETIC PROPERTIES IN PERMALLOY FILMS

Anisotropy aging and stabilization effects have been investigated in vapor-deposited zero-magnetostrictive Permalloy films by annealing either in a rotating magnetic field or in an easy direction field. Two major components in the anisotropy relaxation were observed. Amounts of the two components are comparable in fresh films. By stabilization annealing at 300°C for 35 h, the fraction of the anisotropy affected by the faster component can be made less than 17 of the total initial anisotropy, during which time the relaxation frequency of the slower component gradually decreases from about 10-4 sec-1 to about 10-6 sec-1. The fast component is suggested to be related to high-diffusivity paths in films while reorientation of the ordered atomic pairs as a result of the bulk diffusion process can account for the slow component. However, the vacancy concentration is found to be far in excess of the thermal equilibrium value in fresh films, leading to marked increases in the initial diffusion rates compared with bulk Permalloy values. It is found that the vacancy rate-of-change process follows the chemical rate equation of order 2, which suggests the formation of divacancies. The change-of-slope method is introduced for determination of the activation energy for atomic movement involved in the reorientation process of atom pairs, giving a value of 1.6 eV which is in reasonable agreement with estimates of this quantity from bulk data. © 1969 The American Institute of Physics.