The Taylor–Ulitovski technique was employed for fabrication of tiny ferromagnetic amorphous and nanocrystalline metallic wires covered by an insulating glass coating with magnetic properties of great technological interest. A single and large Barkhausen jump was observed for microwires with positive magnetostriction. Negative magnetostriction microwires exhibited almost unhysteretic behavior with an easy axis transverse to the wire axis. Enhanced magnetic softness (initial permeability, μι, up to 14000) and giant magneto impedance (GMI) effect (up to 140% at 10 MHz) was observed in amorphous CoMnSiB microwires with nearly zero magnetostriction after adequate heat treatment. Large sensitivity of GMI and magnetic characteristics on external tensile stresses was observed. Upon heat treatment, FeSiBCuNb amorphous microwires devitrificated into a nanocrystalline structure with enhanced magnetic softness. The magnetic bistability was observed even after the second crystallization process (increase of switching field by more than 2 orders of magnitude up to 5.5 kA/m). Hard magnetic materials were obtained as a result of decomposition of metastable phases in Co–Ni–Cu and Fe–Ni–Cu microwires fabricated by Taylor–Ulitovski technique when the coercivity increased up to 60 kA/m. A magnetic sensor based on the magnetic bistability was designed.

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We demonstrate composite media with ferromagnetic wires that exhibit a frequency region at the microwave regime with scattering spectra strongly dependent on an external magnetic field or stress. These tunable composite materials have recently been proposed theoretically; however, no direct experimental verification has been reported. We used composite materials with predominantly oriented CoFeCrSiB glass-coated amorphous wires having large magnetoimpedance at GHz frequencies. The free space measurements of reflection and transmission coefficients were conducted in the frequency range 18 GHz in the presence of an external static magnetic field or stress applied to the whole sample. In general, the transmission spectra show greater changes in the range of 10dB for a relatively small magnetic field of few Oe or stress of 0.1 MPa. The obtained results are quantitatively consistent with the analytical expressions predicted by the effective medium arguments. The incident electromagnetic wave induces an electrical dipole moment in each wire, the aggregate of which forms the effective dipole response of the whole composite structure in the radiative near or far field region. The field and stress dependences of the effective response arise from a field or tensile stress sensitivity of the ac surface impedance of a ferromagnetic wire. In the vicinity of the antenna resonance the variations in the magnetoimpedance of the wire inclusions result in large changes of the total effective response. A number of applications of proposed materials is discussed including the field tunable microwave surfaces and the self-sensing media for the remote non-destructive evaluation of structural materials.

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