abstract We studied giant magnetoimpedance (GMI) effect and magnetic properties of Fe 70.8 Cu 1 Nb 3.1 Si 14.5 B 10.6 and Fe 71.8 Cu 1 Nb 3.1 Si 15 B 9.1 Finemet microwires. We observed that GMI effect and magnetic softness ofglass-coated microwires produced by the TayloreUlitovski technique can be tailored either controllingmagnetoelastic anisotropy of as-cast FeCuNbSiB microwires, and/or controlling their structure by heattreatment or by changing the fabrication conditions. High GMI effect has been observed in as-preparedFe-rich and heat treated microwires with nanocrystalline structure. 2014 Elsevier Ltd. All rights reserved. 1. IntroductionStudies of magnetic properties of glass-coated ferromagneticmicrowires (typically of 5e30 m m in diameter) have attractedgrowing attention in the last few years, owing to their outstandingsoft magnetic properties (magnetic bistability, enhanced magneticsoftness, giant magnetoimpedance (GMI) effect, fast domain wallpropagation) and the possibility to obtain glass-coated microwireswithdifferentstructure(amorphous,nanocrystalline,granular)[1e3].Particularly,recentstudieshavedemonstratedthatoptimizationof soft magnetic properties and GMI effect of amorphous glass-coated microwires is possible choosing the appropriate chemicalcompositionofmetallicnucleusandadequateannealingconditions[3].GMI effect consisting of a large change in the impedance of amagnetically soft conductor submitted toan applied magnetic fieldis particularly interesting for magnetic sensors applications, basi-cally due to a magnetic field extremely high sensitivity, suitable forlow magnetic fields detection [4,5]. GMI effect has been success-fully explained in terms of classical electrodynamics through theinfluence of magnetic field on the penetration depth of the elec-trical current flowing through the magnetically soft conductor[4,5]. Cylindrical shape, and the high circumferential permeabilityobserved in Co-rich amorphous wires with a vanishing magneto-striction constant are quite favorable for the achievement of highGMI effect [4e6].In some cases, the nanocrystallization allows achieving a goodmagnetic softness and enhanced GMI effect in ferromagneticmicrowires. Such soft magnetic character is usually attributed tothe vanishing magnetocrystalline anisotropy and the very smallmagnetostriction value, when the grain size approaches 10 nm [7e9]. Like for conventional nanocrystalline materials, the averageanisotropy for randomly oriented