Oblique Incidence Evaporated Iron Films

Abstract

Magnetic hardness in thin metallic films has been sought and achieved by a number of different techniques, including oblique incidence evaporation in a vacuum. Previous studies of oblique incidence evaporation of Permalloy and iron have shown that the easy axis rotates from a direction transverse to the plane of incidence to a direction parallel to the plane of incidence, at an angle of deposition θ=65° with respect to the substrate normal. In this paper we studied the dependence of coercivity, squareness, and uniaxial anisotropy of iron films on thickness (100–1500 Å), with the angle of incidence of the vapor flux as a parameter (θ=40°–85°). We found that at all angles of incidence studied, the coercivity increases with increasing thickness, reaching a peak at about 400 Å, and decreasing monotonically for larger thickness. The uniaxial anisotropy in the transverse direction reaches a peak for θ=55°, while for θ>65° the uniaxial anisotropy in the parallel direction predominates, and increases rapidly with increasing θ. The difference between the coercivities in the transverse and parallel directions decreases with increasing thickness for θ<65° and is independent of thickness for θ>65°. The results are interpreted on the basis of chain and columnar particle growth proposed by previous authors.