Influence of the electrical resistivity of a ferromagnetic thin film on its permeability measurement performed with a permeameter

Abstract Complex permeability μ (= μ ′− j ⋅ μ ″) of a Permalloy Ni 80 Fe 20 thin film, deposited on a 0.5 mm thick glass substrate, is investigated in the frequency range from 0.15 to 6 GHz using a single-coil method. The results reveal that the frequency-dependent permeability is affected by the way to determine the RLC parameters, describing the cell, which allow extending this broad band technique up to 6 GHz. We show that the interaction between the electric field E , of the TEM mode propagated by the coil, and the electrical resistivity of the ferromagnetic layer can be taken into account experimentally. In this case, the RLC parameters are determined from a preliminary impedance measurement of the cell loaded with the ferromagnetic thin film along its easy axis. Our results are compared with a theoretical spectral permeability assuming a gyroresonance mechanism and an in-plane uniaxial anisotropy in the Permalloy thin film. A very good agreement is obtained with the experimental results and leads to the determination of a constant K that describes the permeameter. Then, permeability measurements are first performed on a ferrimagnetic composite made of Ni 0.5 Zn 0.5 Fe 2 O 4 spinel ferrite embedding in a non-magnetic matrix. For a 650 μm thick sample, we point out that the single-coil method is well adapted to measure the high-frequency permeability up to 6 GHz of ferrite composite materials without involving long computations and precise clearances for the samples.