Some recent problems in the field of microwave ferrites

Abstract

Some recent developments and problems in the field of microwave ferrites will be reviewed. Properties which are considered interesting will be presented and discussed for materials with new chemical formulas in the spinel and garnet diagrams. Then we shall give an example of the physico-chemical problems brought up by the synthesis of ferrites with very low dielectric losses. Among the problems related to the micro-structure, materials with very small grains and those without porosity will be examined. The cation distribution between the crystallographic sites will be studied in another chapter. Then we shall try to discuss the experimental data available on microwave relaxation in polycrystalline ferrites. For that purpose, the effects of the relaxing ions and of the granular structure will be compared on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\DeltaH, \DeltaH_{eff}</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\DeltaH_{k}</tex> .