Anisotropy in Permalloy Films

Evaporated films of Permalloy are found to be uniaxially anisotropic under all the conditions of preparation studied so far, including deposition in dc, zero, and rotating-circular magnetic fields. Three principal effects have been identified as contributing to this anisotropy, namely; (1) the formation of directed Fe pairs in the Ni matrix, (2) an effect due to the angle-of-incidence between the substrate and the depositing beam, and (3) anisotropic stress in combination with the isotropic magnetostriction. The evidence for directed pairs comes from the compositional dependence of the anisotropy; the angle-of-incidence effect is demonstrated by depositing onto tilted substrates; anisotropic stress effects are shown by detaching the film from the substrate. The simultaneous presence and interaction of the above effects is thought to be the reason for the variability in the anisotropy which is encountered in Permalloy films.