Analysis of Demagnetizing Effects on Microstrip Line Type Probe for the Permeability Measurement of Thick Specimen

Abstract

This study analyzed the demagnetizing effect for a permeability measurement of a thick NiZn ferrite sheet (100 m thickness) applied using a microstrip line type probe. The ferromagnetic resonance of the NiZn ferrite sheet was observed by two probes with different width conductors. The FMR frequency decreased as the offset between the microstrip conductor and the specimen increased. The two demagnetizing factors were estimated using the ferromagnetic resonance and FEM analysis, and the two values were almost equal. We simulated permeability using FEM, considering the intrinsic permeability of NiZn ferrite (evaluated using the Nicolson-Ross-Weir method) and the demagnetizing effect. The simulated permeability roughly corresponded with the measured value of the microstrip line type probe with a narrow conductor (0.36 mm wide). These results show that the demagnetizing effect is dominant for the high frequency permeability measurement of the thick specimen.