Size effect on magneto-impedance in layered films

The analysis of magneto-impedance (MI) in a sandwich film having an inner conductive lead and two soft ferromagnetic layers is concerned with the role of the film dimensions in determining the MI ratio. The equation for the AC magnetic field distribution in the sandwich is solved making the assumption of a weak skin-effect and a large transverse permeability of the magnetic layers. The flux leakage through the conductive layer results in a considerable drop in MI ratio if the film width is less than a certain critical value depending on the transverse permeability and the layer thickness. This process is similar to that known in inductive recording head, for example, in contributing to head efficiency.