Asymmetrical magneto-impedance effect in Fe-rich amorphous wires

Magnetoimpedance and magnetic properties of Fe-rich ferromagnetic amorphous wires of 0.050 mm diameter, prepared by an in-rotating-water technique following by a cold-drawing process to reduce the initial diameter of 0.125 mm, have been studied. A high value of magnetoimpedance phenomenon (about 60% real component and about 300% imaginary component) was measured in these microwires submitted to stress annealing by using the current annealing technique (annealing parameters: 150 mA during 90 min and 200 MPa). The application of a dc bias current affects strongly the field dependence of the magnetoimpedance ratio, inducing asymmetrical shape to the magnetoimpedance ratio. Such asymmetrical character is associated with the intrinsic helical anisotropy. The dc circular magnetic field produced by the dc electric current can modify in different ways the surface domain structure. (C) 2004 American Institute of Physics.