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[Display omitted] • A novel in-situ method to measure complex magnetic permeability (CMP) based on the magnetic shielding mechanism is presented. • By measuring the magnetic field at the center of shielding, the effective CMP of a large dimensional ferrite shielding can be determined. • The addition of Co significantly improved the thermal stability of CMP by 6.62 times and reduce the magnetic noise. • This method ensures a real-time observation of CMP and magnetic noise under different temperatures. Magnetic shielding made of low noise ferrite materials is used in many ultra-sensitive measurements. The complex magnetic permeability (CMP) of ferrites directly affects the magnetic shielding performance, so the measurement of CMP is particularly important. Conventional measurements omit the effects of temperature on ferrites' magnetic properties and can only measure samples with specific shapes. Here a novel measurement method of CMP based on the magnetic shielding mechanism is presented. By in-situ measuring the magnetic field, the effective CMP of large dimensional ferrite shielding can be determined. Also, the intrinsic magnetic noise of a MnZn ferrite shielding was observed using the proposed method. Using the finite elements method (FEM), we identified the influencing factors of air gap in the CMP measurements. We also analyzed the influence of element doping on the thermal stability of CMP. This study ensures a real-time observation of CMP and magnetic noise under different temperatures. [ABSTRACT FROM AUTHOR]

An overview of transmission/reflection-based methods for the electromagnetic characterisation of materials is presented. The paper initially describes the most popular approaches for the characterisation of bulk materials in terms of dielectric permittivity and magnetic permeability. Subsequently, the limitations and the methods aimed at removing the ambiguities deriving from the application of the classical Nicolson–Ross–Weir direct inversion are discussed. The second part of the paper is focused on the characterisation of partially conductive thin sheets in terms of surface impedance via waveguide setups. All the presented measurement techniques are applicable to conventional transmission reflection devices such as coaxial cables or waveguides. [ABSTRACT FROM AUTHOR]

• A novel methodology is proposed for estimating relative magnetic permeability of magneto-rheological elastomers (MREs). • Determination of a reliable nonlinear B-H curve for MREs. • Unlike the VSM devices, the proposed method yields permeability of MREs under tension/compression mechanical loadings. • It is shown that the proposed method yields an accurate estimation of magnetic permeability with minimal cost and complexity. Identifying a reliable nonlinear B-H curve for magneto-rheological elastomers (MREs) is a fundamental necessity for modeling and optimal design of MRE-based devices, particularly in the initial design stages. The main contribution of this study is to propose a novel methodology for the accurate estimation of magnetic permeability and nonlinear B-H curve for MREs. The proposed method involved three series of simple experiments employing an air gap electromagnet, which required only a Gauss meter to measure air gap magnetic flux density, together with formulation of an equivalent magnetic circuit (EMC). The data acquired from the first two series of experiments were used to characterize the relative magnetic permeability of MREs, while that obtained from the third series of experiments permitted an accurate estimation of the nonlinear B-H curve. For this purpose, isotropic MRE samples with 30% particle volume fraction were fabricated. Results showed that the relative magnetic permeability of MREs decreases with increasing magnetic field. The effectiveness of the proposed methodology for estimating magnetic permeability was demonstrated by comparing with that obtained from a VSM device, which revealed relatively low prediction error of 4.1%. The proposed method could thus be utilized for characterization of nonlinear magnetic permeability of MREs with minimal complexity and cost. The proposed methodology, unlike the VSM devices, could predict magnetic properties of MRE under tension/compression loadings. [ABSTRACT FROM AUTHOR]

A new probe which utilises a dual‐ridged waveguide to provide broadband, non‐destructive (ND) material characterisation measurements of a perfect electric conductor (PEC)‐backed material is introduced. The new probe possesses a bandwidth similar to existing coaxial probes and is structurally robust like rectangular waveguide probes. The combinations of these two qualities make it especially attractive for ND inspection/evaluation applications in the field. The theoretical development of the dual‐ridged‐waveguide probe is discussed. A magnetic field integral equation is derived by applying Love's equivalence theorem and enforcing the continuity of transverse fields at the dual‐ridged‐waveguide aperture. The magnetic field integral equation is then solved for the theoretical reflection coefficient using the method of moments. The permittivity and permeability of the material under test are found by minimising the root‐mean‐square difference between the theoretical and measured reflection coefficients using non‐linear least squares. To validate the new probe, experimental results are presented of a magnetic absorbing material comparing results obtained using the new probe with those obtained using a traditional, destructive technique. The probe's sensitivity to sample thickness, flange‐plate thickness, cutoff wavenumber and measured S‐parameter uncertainties is also investigated. [ABSTRACT FROM AUTHOR]

We present a method for estimating the bandwidth and the measurement errors of the shorted transmission line method used to obtain the permeability and the permittivity of magnetic materials. The permeability and the permittivity of a toroidal test sample are determined by measuring the reflection coefficients of a shorted coaxial transmission line and by using Newton's minimization algorithm. The permeabilities of two samples with different concentrations of cobalt nanoparticles are measured, and the validity of the shorted transmission line method is confirmed by comparing the results to a two-port transmission line approach. The sensitivity of the shorted line method to different measurement parameters is investigated in detail, and the connection between the spatial dimensions of the sample and the measurement uncertainty is studied. The bandwidth of the method is limited by the cavity resonance at the upper end of the frequency range and by the reduction of the sensitivity at the lower end. This is important because in magnetic materials research the sample sizes are generally small, which sets a limit to the lowest measurement frequency using transmission line methods. The reduction in sensitivity is demonstrated by measuring the permeability of three Teflon samples (each having different lengths), and by developing a theoretical model for the measurement errors. [ABSTRACT FROM AUTHOR]

A method for simultaneous measurement of both complex permeability and permittivity is presented using a multilayered conductor-backed coplanar waveguide (MCBCPW) structure to evaluate the possibility of MCBCPW as a sensor for nondestructive electromagnetic measurement. Formulae and methods are developed to extract the electromagnetic parameters of material under test (MUT) placed on the topside of CPW. The measurement results for magnetic powder on MCBCPW sensor showed good agreement with those using coaxial sensors. The method allows both permittivity and permeability to be measured in a single-step measurement without modifying or reshaping the material, making this method particularly attractive for inhomogeneous materials such as biological materials. [ABSTRACT FROM PUBLISHER]

A broad-band technique for determining the electromagnetic properties of isotropic film-shaped materials, which uses a microstrip line, is presented. Complex permittivity and permeability are computed from analytical equations and S-parameter measurements of microstrip cells propagating the dominant mode. Measured εr and μr data for several materials are presented between 0.05 GHz and 40 GHz. This technique shows a good agreement between measured and predicted data [ABSTRACT FROM PUBLISHER]

We have developed a new permeance meter in the 1 MHz-1.5 GHz range using either a microstrip pickup coil or a shielded loop pickup coil. Both pickup coils and the driving plates are free from LC resonance due to impedance matching. In the MHz range we must consider signal-to-noise ratio of the pickup coil. In the GHz range we must eliminate the voltage induced by the electric field, and an electromagnetic higher order mode in the driving plates. [ABSTRACT FROM PUBLISHER]

A swept frequency method for measuring the magnetic permeability of thin films for frequencies up to 2 GHz with a resolution at 1 GHz of /spl sim/0.1 /spl mu/m in permeance is described. It is based on the measurement of impedance of a strip loop loaded with the sample under test. The method employs a commercial impedance or network analyzer, is simple, and suitable for permeability measurements of thin magnetic films which are used in recording heads and microwave components. [ABSTRACT FROM PUBLISHER]