Permeability Measurements of Amorphous Coatings Prepared with Fine Magnetic Particles

Amorphous or granular magnetic coatings formed with magnetic particles have high resistivities, which are desirable to reduce the eddy current t losses greatly. However, since magnetic particles are separated from one another, the permeabilities of magnetic coatings tend to be low, and obtaining accurate permeability spectra can be not so trivial. The measured relative permeability of FeSiB coating at 30 MHz was 21.5, while the expected value based on 4piM_s and H_k values was 5.4. The modifications in calibration procedure allow more accurate measurement of permeability of magnetic films with intermediate or low permeability and hence enable the permeameter to cover the wider range of the permeability values.