Ni0.2Zn0.3Fe2.5O4 films (15 μm thick) were deposited by spin spray ferrite plating from an aqueous solutionsonto polyimide sheets at 90.C. Their peel test andhigh-frequency permeability as well as noise suppressioneffects were investigated. The oxygen plasma treatment onpolyimide sheet surface improved the film adhesion. Therewas not visible crack on the bended film surface for the Ni-Zn ferrite film thinner than 2 μm and was not peeled offeven after the bending test of a million times. The films exhibitedexcellent high-frequency permeability profile and anatural resonance frequency (where the imaginary permeabilityreaches a maximum) fr was 370 ± 30 MHz. Thetransmission loss increased with the film thickness, reachingthe maximum _Ploss = 70% at 8 GHz for the 5 μm-thickfilm. The reflection loss in the measured frequency rangewas S11 < 10% which is small enough for films to be usedas the conducted noise suppressors. The value of _Ploss obtainedfor the 5-μm thick film was about 15% higher thanthat (_Ploss = 55%) attained by the commercialized 50-μmthick noise suppressing sheet.
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