C. P. Neo

High frequency complex permeability of iron particles in a nonmagnetic matrix

The effective permeability (μeff) was measured and calculated for composites consisting of micron- or submicron-sized nanocrystalline iron particles embedded in a nonmagnetic matrix. The intrinsic permeability of iron particles was obtained from the calculation for a random spatial distribution of magnetic domains and its analytical model is derived from the Landau-Lifshitz-Gilbert equation. In the calculation, each grain is assumed to be a single magnetic domain because of its nano size. The effective permeability was calculated using three methods—Bruggeman’s effective medium theory, extended Bruggeman’s effective medium theory with the consideration of the skin effect, and a simulation method which was developed in the present work. The skin effect was considered in our simulation work. Our simulation agrees well with the experimental data. Our work has shown clearly that the magnetic domain structure with a random spatial distribution of magnetic easy axes and the skin effect need to be considered to ...

Calculation of complex permeability of magnetic composite materials using ferromagnetic resonance model

The Landau–Lifshitz–Gilbert (LL-G) formula has been widely used in modeling of complex permeability of magnetic thin films and particle composites. In this paper, a approach which is based on Landau–Lifshitz ferromagnetic resonance (LL-FMR) model has been developed to calculate the complex permeability of magnetic particles/insulator matrix composite. It has found that the LL-FMR model can be used to compute the intrinsic permeability of a magnetic particle with different alignments of its magnetic domains with the respect to the incident wave. Through integration with respect to its resonant frequency, this method offers a neat closed-form formula for the case of isotropic composite. Its results compared relatively well with our previous method which computes the isotropic permeability by taking the average of the permeability of a large number of randomly oriented magnetic domains with respect to incident wave based on the LL-G model. For carbonyl bcc-Fe and Fe3O4, the calculated permeability agrees rel...

Smith chart approach to the design of multilayer resistive sheet

The design of the multilayer resistive sheet is often given in some formulae or in some tabulated forms. The electrical engineer or material scientist often cannot visualize how the design really works or the achievable bandwidth. In this paper, we attempt to give a good understanding of the design of the multilayer resistive sheet by using the Smith Chart approach. The Smith Chart approach offers more flexibility to the design of the multilayer resistive sheet, as compared to published formulae or tables.

An algorithm to extract effective magnetic parameters of thin film with in-plane uniaxial magnetic anisotropy

The calculation of high frequency complex permeability of thin ferromagnetic film requires the measured values of its saturation magnetization, anisotropic magnetic field intensity, resistivity, and thickness. It is often observed that the calculated permeability using the Landau–Lifshitz–Gilbert (LLG) theory does not agree well with the measured permeability of thin film with in-plane uniaxial magnetic anisotropy, owing to the measured anisotropic magnetic field intensity, saturation magnetization, etc., are not effective values at high frequency. In this work, the Landau–Lifshitz ferromagnetic resonance model is modified to take the skin depth effect into consideration. In the comparison study, its calculated magnetic permeability curves (real and imaginary) agrees very well with those calculated from the LLG model. In addition, an algorithm process to extract effective magnetic parameters (saturation magnetization Ms, magnetic anisotropy field Ha, and damping factor α) has been developed. The algorithm...