Large GMI effect in Co-rich amorphous wire by tensile stress

Abstract

Quality Co68Fe4.5Si15B12.5 amorphous wires are fabricated and their giant magneto impedance (GMI) effect are investigated at frequencies ranging from 0.1 to 20MHz with or without tensile stress applied. Experimental results indicate that the GMI effect of these wires can be effectively improved by applying a small axial tensile stress. There is a pronounced increase from 1.3% to 47.3% in impedance ratio at 0.6MHz when a stress of 103MPa is applied. The GMI response is further increased to 261% by doing so at 15MHz. The field sensitivity of these wires is optimized and it increases from 0.55 to 2.73%/(A/m) at 0.6MHz and it is proved that the most sensitive field response is obtained by applying a tensile stress of 84.5MPa below 1MHz. With reference to the stress evolution of sensitivity at varying frequencies, the maximum field sensitivity shifts to a lower stress with increasing frequency. Quantitatively, a stress as small as 18.4MPa is enough to yield a field sensitivity as high as 6.7%/(A/m) at 15MHz. This demonstrates the possibility of achieving small stress (<100MPa) induced large enhancement of GMI effect and field sensitivity at frequencies of several tens of MHz that are of much technical interest in sensor applications.