Some Properties of Ferrites in Connection with Their Chemistry

After an elementary introduction on the origin of magnetism, intended for the reader who is not acquainted with the subject, it is shown how the molecular-field hypothesis can account for the magnetic properties of ferromagnetics and antiferromagnetics, and for the noncompensated antiferromagnetics, with which latter materials we are concerned here. A brief description of the spinel lattice is given, and an account of the crystal chemistry of the spinels which is necessary to understand the experimental saturation magnetizations which are discussed. A short survey of methods of preparation is given. The second part discusses the anisotropies, and some of the magnetization processes which influence permeability, and the factors which influence high-frequency permeability and losses. Among these are the ferromagnetic resonance phenomenon and the dimensional resonance and relaxation phenomena. In this part the way in which these factors are influenced by chemical composition and preparation technique is indicated. Finally, a short history of the development of the ferrites is given