Stress in Evaporated Ferromagnetic Films

Abstract

Ferromagnetic resonance and oscillation magnetometer measurements on a thin evaporated nickel film annealed in a magnetic field are described. Observations of the dependence of the resonant field magnitude on the angle in the plane of the film between the direction of the magnetic field during annealing and the static resonance field direction show that magnetic annealing produced a preferred magnetic axis in the plane of the film. The good agreement between theory and experiment allows one to establish that the film had bulk-nickel $g$ and saturation magnetization values, a large isotropic tension in the plane, and a lesser uniaxial compression in the plane in the direction of the preferred magnetic axis. In the light of these results, it is suggested that part of the discrepancy between theory and ferromagnetic resonance experiments found recently by Conger and Essig for the dependence of saturation magnetization on evaporated film thickness may have arisen from their omission of stress corrections to the resonance condition. Further, part of the difference between film switching times derived from resonance line widths and those directly measured on the same films by these authors may have been caused by the narrowing of ferromagnetic line widths for thin films, as compared with bulk material, produced by the strong dependence on resonant absorption of power transmission entirely through sufficiently thin films.