A review of new magnetic phenomena

At a result of new developments, the classical concepts of magnetic materials, characterized by hysteresis loss and eddy currents, are no longer adequate. Study of the ferrites has revealed new and important magnetic phenomena. These materials, because of their high resistivities and correspondingly low eddy currents, exhibit useful magnetic properties at frequencies well above those at which magnetic alloys are applicable. This paper reviews the new phenomena — domain wall motion and dimensional effects in the low megacycle region, and ferromagnetic resonance and the Faraday effect in the microwave region — and relates them to modern theory. Some possible microwave applications are discussed briefly.