Optimization of mechanical and giant magneto‐impedance (GMI) properties of melt‐extracted Co‐rich amorphous microwires

Abstract

In this work, we report a comprehensive investigation on mechanical and giant magneto‐impedance (GMI) properties of melt‐extracted Co‐rich amorphous microwires with the nominal composition of Co69.25Fe4.25Si13B13.5−xNbx (x = 0, 1, 2, 3, 4). Results show that the tensile strength and GMI properties gradually increase with the substitution of B by Nb at first, and then decrease with a further Nb substitution. The melt‐extracted microwires with the substitution of B by 3% Nb exhibit a maximum tensile strength σm of 4000 ± 50 MPa owing to the formation of nanosized crystals in the amorphous matrix. In addition, the substitution of B by 1% Nb assures an excellent GMI property. At 5 MHz, the maximum GMI ratio [ΔZ/Zmax]max for the melt‐extracted microwires reaches as high as 450 ± 10% versus 380 ± 10% for traditional CoFeSiB microwires and the field‐response sensitivity increases from 350 ± 10% Oe−1 to 700 ± 10% Oe−1 for 1% Nb substitution. It is thus concluded that both mechanical and GMI properties of the melt‐extracted Co‐based amorphous microwires can be greatly improved by properly adding Nb, and this is promising for many engineering applications, including high‐resolution magnetic, stress and biomedical sensors.