Abstract

In this paper we report novel results on magnetic properties and giant magnetoimpedance (GMI) effect at frequencies between 10 MHz and 500MHz in ultra-thin Co-Fe-rich amorphous glass-coated microwires with near-zero magnetostriction constant and with metallic nucleus diameter ranging between 5 mu m and 22 mu m. Co67.05Fe3.84Ni1.44Si14.47B11.51Mo1.69 glass-coated amorphous microwires with metallic nucleus diameter ranging between 5 mu m and 22 mu m and total diameter between 10 mu m and 23 mu m with vanishing magnetostriction constant of the order of -(1-3) x 10(-7) fabricated by the Taylor-Ulitovsky method were studied. Most of the samples studied exhibited excellent soft magnetic behaviour and a large GMI effect. Off-diagonal components, real and imaginary parts of the GMT were analysed. Even in the thicker samples (metallic nucleus 22 mu m) the penetration skin depth calculated from the GMI curves at 30 MHz was about 1 mu m. m Therefore the surface magnetization process and surface defects are of special importance to achieve good HF properties in these wires. (C) 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim.