Size Effect in the Measurement of Microwave Permeability of Ferrites (Correspondence)

In the usual method of measuring the tensor permeability of ferrites at microwave frequencies, a small sample of the material is placed in a suitable cavity, and the change in resonant frequency and Q of the cavity, caused by the presence of the ferrite, are measured. The measured quantities are related to the quantities of interest-real and imaginary parts of permeability-by equations derived through perturbation theory.