Spin-Wave Resonance of Permalloy Thin Films as Measured in Ultrahigh Vacuum and in Air

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Abstract
Permalloy thin films in the thickness range from 100 to 2530 Å and of melt composition 82% Ni‐18% Fe were deposited in an ultrahigh‐vacuum system and the standing spin‐wave modes (SSWM) of these films were measured in vacuum and in air. The SSWM shifted to higher magnetic fields as the films aged in vacuum, but shifted to lower magnetic fields as they aged in air. Since the SSWM of the films displayed a quadratic dependence on mode number at all times, the observed spectra shifts could be accounted for by changes in g, 4πM, and A/M with no observed changes in pinning. Annealing greatly altered the absorption spectra, indicating that a significant change in the pinning occurred. It is concluded that spin pinning exists in a modest vacuum (p≃1×10−7 Torr) even before the films have been exposed to the atmosphere and that spin pinning is dependent on the substrate used in that spin pinning is greatly affected by annealing.