Measurement of magnetic losses in resonant metallised ferrites

Microwave magnetic losses, far enough from the ferromagnetic resonance, are generally measured by perturbation methods, i.e. by comparing resonance of a cavity with and without magnetic sample. Nevertheless such methods require very accurate apparatuses, for parameters of the resonant cavity are slightly altered by the presence of the sample because of the relative smallness of the latter. The fore-going difficulty can be overcome by using the sample as a resonant cavity. The TM010mode of a cylindrical metallised sample are very convenient to achieve accurate measurement of magnetic losses. This method is quite effectual for materials with low magnetic moments and for low frequencies (from 1 to 5 GHz). Large metallic cavities are avoided and the apparatus is very simple.