Giant Magnetoimpedance Effect of Amorphous and Nanocrystalline Glass-Coated Microwires

Abstract

In this chapter we are reporting on correlation of Giant magnetoimpedance (GMI) effect and magnetic properties of amorphous and nanocrystalline Co-Fe rich glass-coated microwires. We measured the GMI magnetic field, frequency dependences and hysteresis loops of composite microwires produced by the Taylor-Ulitovsky technique. We observed that GMI effect and magnetic softness of glass-coated microwires produced by the Taylor-Ulitovsky technique can be tailored either controlling magnetoelastic anisotropy of as-prepared microwires or controlling their internal stresses and structure by heat treatment. High GMI effect has been observed in as-prepared and annealed Co-rich microwires. In the case of Fe-rich Finemet-type microwires we observed considerable magnetic softening of studied microwires after annealing. This magnetic softening correlates with the devitrification of amorphous samples. Amorphous Fe-rich microwires generally exhibited low GMI effect (GMI ratio below 5 %). Considerable enhancement of the GMI effect (GMI ratio up to 100 %) has been observed in heat treated microwires with nanocrystalline structure. The objective of this reported work is to develop magnetically soft thin wires for applications in magnetic field sensors.