AC and DC-shielding properties for the Ni80Fe20/Cu film structures

Abstract

Multilayered Ni80Fe20/Cu film shields were obtained via electrochemistry method with different thickness and number of partial magnetic layers. Magnetic properties and shielding characteristics were investigated as well as function of thickness and number of layers. Difference in magnetic properties for Ni80Fe20 films with different thickness is due to formation of defect layers on the top and bottom film surfaces during electrodeposition processes. These layers can be characterized as layers with high density defects (as a result poor iron content). Main deviation in magnetic properties is typical for thinner films. It was measured DC and AC shielding and results discussed. Maximal value of DC-shielding effectiveness was observed for multilayered samples with small number magnetic layers with large thickness (80–400μm). The minimal value of DC-shielding effectiveness was observed for the multilayered sample with the minimum thickness of the magnetic layer (5μm) and maximal number of the layers (80 layers). It is in good agreement with shunting mechanism. In low frequency range maximal values of AC-shielding effectiveness were observed like in case of DC-shielding for samples with small number magnetic layers with large thickness. With frequency increasing the situation was radically changed and AC-shielding effectiveness was higher for samples with maximal number of layers. In the frequency range above 40kHz AC-shielding effectiveness was sharply decreased due to sharply decreasing of permeability value. As a result it leads to decrease of absorption loses (SEabs.). It was discussed the main shielding mechanisms for multilayered Ni80Fe20/Cu film samples under different external influences. Main contribution in electromagnetic shielding in the range 300Hz–20kHz is absorption and reflection processes. In the range 20kHz–50kHz main shielding mechanisms are reflection and re-reflection. For 300Hz–50kHz frequency range most appropriate to use multilayered structures with large number of thin layers with cardinally different values of magnetic permeability and electrical conductivity.