Influence of tensile stress on giant magnetoimpedance effect of electroplated Ni1−xCox/Cu composite wires

Enhanced giant magnetoimpedance effect has been observed in Ni1−xCox/Cu composite wires with tensile stress. Ni1−xCox magnetic layers were deposited onto 150 μm diameter copper wires, after that a tensile stress of 128 MPa was applied to the composite wires. The highest GMI ratio of 124% has been obtained, which is 4.5 times larger than the original value of 28%. The influence of tensile stress on GMI effect can be further proved through heat-treatment, which can release the stress and decrease the GMI ratio to original value. GMI ratios decrease with increasing cobalt content, which can be explained by the variation of the magnetostriction constants.