Effect of Electromagnetic Propagation on the Magnetostatic Modes

Abstract

The second‐order effect of electromagnetic propagation on the essentially static‐field distribution of the magnetostatic modes of a ferromagnetic sample is obtained by an iteration‐type technique. The magnetostatic potential constitutes the source in a mathematical sense for a second‐order correct field distribution. The internal sample fields are investigated for a ferrite cylinder enclosed between parallel conducting plates and they are found to consist of resonant modes whose frequencies are determined from a characteristic equation. These frequencies reduce to those of the magnetostatic modes in the limit of vanishingly small wavenumbers. For a nonzero wavenumber the frequencies differ from the corresponding magnetostatic limits by an amount which depends on the sample shape. These resonant frequencies are size‐dependent as contrasted to the size‐independent magnetostatic modes. No resonant frequencies are possible above a critical value that depends on the spacing between the plates. A sample mode, whose resonant frequency is in a region forbidden to the magnetostatic modes, can exist if the sample size exceeds a critical value.