Improvement of Stepped Magnetoimpedance Properties by Controlling the Demagnetizing Effect

We investigated the effects of controlling the distribution of the demagnetizing field on the impedance profiles of stepped giant magnetoimpedance elements. Elements with an ellipsoidal shape were adopted to improve the properties in discontinuous impedance jumps, as the demagnetizing field is expected to be uniform in an ellipsoid. The impedance jumps in the ellipsoidal elements became sharper and more abrupt, and the height ratio improved by 3-4 times compared with the ratio of the conventional rectangular elements. The observed domain structures propagated from the edge to the center in the rectangular elements, which is explained on the basis of the calculated distribution of the demagnetizing factor. On the other hand, all the domains appeared or disappeared in the ellipsoidal elements, indicating that the demagnetizing factor is nearly constant in the elements. The results contribute to a miniaturization of the element in order to keep the abrupt discontinuous impedance.