Permeability characterization of ferrites in the radio frequency range

Abstract

Soft ferrites are employed in applications from the kHz to the GHz frequency range due to its high magnetic saturation, low coercivity fields and high electrical resistivity. Measuring the complex magnetic permeability in the range from low frequencies to the radio frequency may be performed using two complementary techniques: impedance spectroscopy and coaxial transmission line. The procedures to extract the real dependence of the permeability from the experimental measurements are presented. The experimental permeability of three different ferrites are presented and modelled considering two sources of dispersion: the spin rotational magnetization and the domain wall motion. A good fit of the experimental results is obtained for ferrites that display only one dispersion mechanism after applying the required corrections of stray capacitance, Skin effect and electrical conductivity. For the ferrite showing the two magnetization processes, only a rough adjust has been achieved, although it is shown to be comparable to the ones reported in the recent scientific literature