On the Magnetic Properties of Sputtered NiFe Films

Reproducibility and control of magnetic properties have been significant problems in the preparation of Permalloy films by cathodic sputtering. The data presented in this paper illustrate the reduced sensitivity to gaseous impurities that can be achieved by applying a suitable negative bias to an 81% Ni-19% Fe Permalloy film that is being deposited by dc sputtering. Results are shown which compare the magnetic properties as a function of deposition rate achieved with and without a bias potential applied to the film during deposition. Data are also presented showing the effect of film bias on magnetic properties when known concentrations of oxygen and nitrogen are present in the atmosphere during deposition. The evidence shows that the effect of the bias is to reduce the quantity of system atmosphere impurity included in the film. The bias technique has permitted, with good reproducibility, accurate experimental determination of the effect of such control parameters as substrate temperature on magnetic properties. (Wall motion threshold H
0
, anisotropy field H
k0
, and dispersion α
90
are plotted as a function of substrate temperature.) In addition, data are shown which demonstrate the compositional control and simplicity of film thickness and deposition rate control which are inherent in the sputtering process.