Initial Susceptibility Spectra of Permalloy Films

Abstract

The initial susceptibility of Permalloy films from 100 to 10000 Mc/sec is investigated theoretically and experimentally. The exact boundary value problem of a film placed in a rectangular cavity is solved. This result is compared with the simpler solution obtained by means of the Bethe-Schwinger perturbation formula. As may be expected, the exact solution reduces to that obtained from perturbation theory when the film thickness and the value of the initial susceptibility are sufficiently small. In a self-consistent way, we show that exchange effects can sometimes be neglected as far as initial susceptibility values are concerned.