Microwave permittivity and permeability of magnetic wire composites

Abstract

This paper provides a comprehensive review on electromagnetic properties of composites with magnetic microwires. The analysis is made in terms of the effective parameters: permittivity and permeability. The use of magnetic components in wire media makes it possible to realize controllable or tunable materials. A variable magnetoimpedance controls the dispersion region resulting in broadband transmission modulation. The conditions of strong tuning including directional changes in the static magnetization, magnetoimpedance, stress impedance, and optimal skin effect are discussed. Diluted composites with magnetic wires having specific circumferential or helical anisotropy may also have large values of the effective permeability at high frequencies up to few GHz. This is important to design materials possessing the both effective parameters in the same frequency band. Considering the variation in the impedance due to internal stress/temperature distribution, the magnetic wire composites can be regarded as materials with distributed sensors. A range of potential applications for structural health monitoring is discussed.