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.

Abstract:We overviewed the correlation between the structure, magnetic and transport properties of magnetic microwires prepared by the Taylor-Ulitovsky method involving rapid quenching from the melt and drawing of the composite (metallic core, glass coated) wire. We showed that this method can be useful for the preparation of different families of magnetic microwires: soft magnetic microwires displaying Giant magnetoimpedance (GMI) effect, semi-hard magnetic microwires, microwires with granular structure exhibiting Giant Magnetoresistance (GMR) effect and Heusler-type microwires. Magnetic and transport properties of magnetic microwires depend on the chemical composition of metallic nucleus and on the structural features (grain size, precipitating phases) of prepared microwires. In all families of crystalline microwires, their structure, magnetic and transport properties are affected by internal stresses induced by the glass coating, depending on the quenching rate. Therefore, properties of glass-coated microwires are considerably different from conventional bulk crystalline alloys.

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We measured magnetic domain propagation and local domain wall(DW) nucleation in Fe-Co-rich amorphous microwires with metallic nucleus diameters from 2.8 to 18 μm. We found that manipulation of magnetoelastic energy through application of applied stresses, changing of magnetostriction constant, and variation of internal stresses through changing the microwires geometry affects DW velocity. We observed uniform or uniformly accelerated DW propagation along the microwire. The abrupt increasing of DW velocity on v(H) dependencies correlates with the location of the nucleation place of the new domain wall.