Magnetostriction and Compositional Gradients in Boat-Evaporated Permalloy Films

Abstract

Magnetostriction measurements on Permalloy films prepared by vacuum evaporation from a tungsten boat indicate an average Fe enrichment of about 2% above the original melt composition. In addition it is shown that the film composition varies continuously through the thickness from 4% to 7% per 1000 Å for typical evaporation conditions. Compositional gradients of even smaller magnitude are capable of pinning spin waves. Since filament and boat evaporation are used widely in preparing laboratory films, the anomalous spin‐wave results frequently reported in the literature may be due to thickness‐compositional gradients.