Differences in the Magneto-Impedance of FeNi/Cu/FeNi Multilayers With Open and Closed Magnetic Path

The performance of the magnetoimpedance effect in terms of magnitude and sensibility is evaluated for two FeNi/Cu/FeNi multilayer structures with different geometries, such that in one of them the magnetic layers are in contact at the edges, presenting a closed magnetic path that is absent in the other. Magnetization measurements by Kerr effect and magnetic domain observations are used to characterize the samples. The results show that the sample with the closed magnetic path performs better, reaching a value of 38 % of variation of the impedance and a sensibility of about 5%/Oe at 325 MHz. However, at lower frequencies the sample with open magnetic path presents higher values of the magnetoimpedance effect and its sensitivity than the one with the closed magnetic path. Finite element simulations confirm that this behavior is a direct consequence of the geometry of the samples.