Glass-coated amorphous ferromagnetic microwires at microwave frequencies

The objective of the present investigation is to outline some of the more relevant microwave properties of glass-coated amorphous magnetic microwires. The introductory section includes a brief description of the quenching and drawing preparation procedure that determines their cylindrical shape, their amorphous nature and the presence of the glass coating. The shape and magnetoelastic (stresses and magnetostriction) anisotropy terms imposed by those characteristics finally determine the microwave properties. Subsequently, a description is given of the circumferential, parallel and transverse excitation configurations of the electric and magnetic fields in the study of microwave response. The dynamic properties of the microwires are discussed for the three configurations. Particularly, the correlation between giant magnetoimpedance effect and ferromagnetic resonance (FMR) at various working frequencies is analysed for the circular magnetic field configuration. The influence of magnetoelastic anisotropy through mechanical stresses is investigated through the changes in the parallel permeability for microwires with different coating thickness. The role of magnetoelastic anisotropy through the magnetostriction constant is analysed through the scattering parameters and the change of FMR frequency for microwires with different alloy composition. Finally, the electromagnetic properties of microwires embedded in polymeric matrices are envisaged.