Angle-of-Incidence Anisotropy in Evaporated Nickel-Iron Films

The magnetic anisotropies of iron, nickel, and permalloy films, evaporated onto glass substrates at various incident angles and substrate temperatures, have been measured by a torque method. For all compositions, the largest absolute value for the magnetic anisotropy occurs at the largest incident angle and lowest substrate temperature. A detailed calculation of the anisotropy resulting from a [111] fiber axis is found to fail to agree with the experimental results either in order of magnitude or in direction of the easy axis. The change in the magnetic anisotropies of films after removal from substrates is small enough that macroscopic stress cannot be the source of the anisotropy. A difference in electrical resistance parallel and perpendicular to a direction defined by the vapor stream during deposition is found to vary qualitatively very much like the magnetic anisotropy, both with film composition and incident angle. It is concluded that deposition at an angle of incidence produces an anisotropy in structural imperfections, which are interpreted in terms of shape and surface magnetic anisotropies as well as magnetostrictive effects.