Deposition Temperature and Compositional Dependence of Negative Anisotropy in Nickel-Iron Films

Abstract

An investigation of the deposition temperature (200° to 350°C) and compositional (80% to 87% Ni) dependence of negative anisotropy (K−) in nickel-iron films has been made. The results indicate that the number of K− regions is zero below a critical temperature which depends on composition and increases with increasing temperature; the more negative the magnetostriction λ (λ<0 for % Ni>83), the lower the critical temperature. The following qualitative hypothesis is suggested for the origin of K− regions: It is known that deposited metal films have a real surface area much larger than the macroscopic area of the deposit. Thus the films are actually porous and mass diffusion between adjacent crystallites occurs in order to lower surface energy at the expense of strain energy. If the mass diffusion were anisotropic, for example, by depending on the direction of M, then anisotropic strain would be generated. The resulting anisotropic strain coupled to ± magnetostriction would then generate local K± (or K∓ since the sign of the strain has not been specified) regions.