The effects of metallic underlayers on Properties of permalloy films

Abstract

Thin Permalloy films of zero-magnetostrictive composition were evaporated on a variety of metal film underlayers of various thicknesses (which were deposited on glass substrates) and also on smooth metallic substrates. In contrast to Prosen et al., however, the observed uniaxial magnetic anisotropy is not zero. In thin Permalloy films (100-1000 Å) deposited on high melting-point metal films (Mo, Ti, Pd, and Cr), essentially the same anisotropy field is obtained as is normally observed on glass substrates. In these films the coercivity and the angular dispersion increase slightly as the underlayer thickness increases. Permalloy properties on low melting-point metals (Au, Ag, Cu, and Al) depend strongly upon the underlayer thickness. At a given substrate temperature, a maximum in coercivity and angular dispersion is found in ∼100 Å thick underlayers of Au, Ag, and Cu. In Al underlayers, the values of coercive force along the easy and hard axis increase rapidly as a function of thickness. Large values of the easy-axis skew are obtained in all metal underlayers where the direction of the skew depends upon the geometrical arrangement of the vapor source (Permalloy) and the substrate. These effects are attributed to the microstructure and morphology of the underlayers. Electron microscopy studies are presented in confirmation of these surface geometrical effects.