Magnetic annealing of NiFe films that possess a stable structure

The magnitude of the anisotropy field, HK, has been measured during magnetic annealing of vapor-deposited NiFe films that possess an axis of uniaxial anisotropy. In order to achieve a stable structure, and thereby eliminate contributions from simultaneous metallurgical processes, the films were recrystallized at a temperature higher than any of the subsequent annealing temperatures. It was observed that one fundamental process dominated the annealing, characterized by an average activation energy of 2.4 eV. This activation energy agrees well with the activation energy for self-diffusion in NiFe alloys. The composition dependence of the activation energy for magnetic annealing reveals a minimum near Ni3Fe. Since the diffusion of Ni, but not Fe, in NiFe alloys exhibits a similar minimum, it appears that the diffusion of Ni is the rate-controlling process. The magnitude of the maximum values of HK obtainable by magnetic annealing are also presented.