Ferromagnetism at Very High Frequencies. III. Two Mechanisms of Dispersion in a Ferrite

Abstract

The magnetic spectrum of a ferrite is shown to contain two regions of pronounced dispersion. One occurs at radiofrequencies, resembles a resonance, and is proved to be due to domain wall displacements; the other occurs in the microwave range, exhibits typical resonance characteristics, and is attributed to domain rotations. The identification of the dispersion mechanisms is based primarily on a comparison of the complex permeability of solid samples with that of small particles of the same material. Several manifestations of single-domain behavior are reported, and a study of remanence by high frequency methods is presented. The wall effects are interpreted in terms of the concept of apparent wall inertia and it is shown that microscopic eddy currents cannot cause the damping. The rotational effects are interpreted on the basis of crystalline anisotropy. Previously used methods for identifying dispersion mechanisms are discussed.