Stress-dependent magnetoimpedance in Co-based amorphous wires with induced axial anisotropy for tunable microwave composites

A remarkably strong dependence of magnetoimpedance (MI) on tensile stress has been observed in the microwave frequency range for thin CoFeCrSiB glass-coated microwires with an axial anisotropy induced by tension annealing. The relative change in impedance runs into more than 100% at 0.5-1.5 GHz for a characteristic stress of 600 MPa. It was demonstrated that this stress MI is due to the transformation of the anisotropy from the axial toward the circumferential under the effect of applied tension and does not require the assistance of the dc bias magnetic field. Such microwires incorporated into a dielectric matrix may constitute a new sensing medium that is characterized by the stress-dependent effective permittivity. The proposed medium can be used for the microwave visualization of the stress distribution inside of a composite structure or on its surface.