Magnetic Spectra of Ferrites
- 1 January 1953
- journal article
- research article
- Published by American Physical Society (APS) in Reviews of Modern Physics
- Vol. 25 (1) , 81-89
- https://doi.org/10.1103/RevModPhys.25.81
Abstract
A brief discussion is given of the meaning of initial permeability, the principles of its measurement, and the nature of "dimensional resonance." In considering magnetic spectra containing only a single resonance, typical data on sintered ferrites and on finely divided ferrite powders are reviewed, and some of the theoretical interpretations previously advanced are criticized. The investigations involving the two natural resonances found at this laboratory in a commercial Mg-ferrite are then summarized, including resonance in single-domain particles as a method for identifying dispersion mechanisms, experimental evidence for the inertia of domain walls, the nature of internal fields, and the temperature dependence of the natural resonances and of the spectroscopic splitting factor. Using the information obtained from these special studies, the following general hypothesis is advanced: In principle, two natural resonances are present in the magnetic spectrum of any sintered ferrite, and the single resonance sometimes observed represents the coalescence of two resonances. Reasons are given for expecting this coalescence to occur in some materials only, as in certain sintered mixed ferrites containing Zn-ferrite. The new hypothesis is consistent with all presently available data, including new spectra, some containing two resonances, that were recently obtained on pure ferrites at this laboratory. Additional confirmatory experiments are described which provide methods for separating or coalescing two resonances, and permit distinguishing between internal fields due to anisotropy and magnetic interactions. The limitations and possibilities of ferrites for obtaining useful microwave permeabilities are discussed from the new viewpoint, the criteria involved in this problem being shown to differ from those used at radiofrequencies.Keywords
This publication has 27 references indexed in Scilit:
- Dispersion and absorption in magnetic ferrites at frequencies above one Mc/sPublished by Elsevier ,2004
- Ferromagnetism at Very High Frequencies. IV. Temperature Dependence of the Magnetic Spectrum of a FerritePhysical Review B, 1952
- Motion of a Ferromagnetic Domain Wall inPhysical Review B, 1952
- The magnetization process in ferritesPhysica, 1951
- The Magnetization Process in FerritesPhysical Review B, 1951
- A note on the ferromagnetic Faraday effect at centimetre wavelengthsJournal de Physique et le Radium, 1951
- Ferromagnetism at Very High Frequencies. III. Two Mechanisms of Dispersion in a FerritePhysical Review B, 1950
- Properties of Single Crystals of Nickel FerritePhysical Review B, 1950
- Dimensional Effects Resulting from a High Dielectric Constant Found in a Ferromagnetic FerritePhysical Review B, 1950
- Gyromagnetic Resonance in FerritesNature, 1947