Tuning of giant magnetoimpedance effect of amorphous and nanocrystalline microwires

Composite structural materials containing periodic or random arrays of metallic wires often referred to as wire metamaterials have a strong dispersion of the dielectric function in the GHz frequency band. These metamaterials utilising thin ferromagnetic wires exhibiting magnetoimpedance effect present tuneability of the effective permittivity, by a weak magnetic field or a mechanical stress. We present our studies of the factors affecting soft magnetic properties and giant magnetoimpedance effect (GMI) in thin amorphous and nanocrystalline microwires. We showed that the magnetoelastic anisotropy is one of the most important parameters that determine magnetic softness and GMI effect of glass-coated microwires and annealing can be very effective for manipulation the magnetic properties of amorphous ferromagnetic glass-coated microwires. Considerable magnetic softening and increasing of the GMI effect is observed in Fe-rich nanocrystalline FINEMET-type glass-coated microwires after the nanocrystallization.