Ni-Zn ferrite films with high permeability (μ′=∼30, μ"=∼30) at 1 GHz prepared at 90 °C

Ni-Zn ferrite films were prepared by spin-spray ferrite plating method at 90 degreesC on glass substrates from a reaction solution of FeCl2(+FeCl3)+NiCl2+ZnCl2 and an oxidizing solution of NaNO2+CH3COONH4. The complex permeability mu=mu'-imu" values of the as-plated films were measured at frequencies up to 3 GHz. The Ni0.28Zn0.18Fe2.54O4 film 0.40 mum in thickness plated using the mixture of Fe2+ and Fe3+ as iron ions exhibited a high mu' of around 42 and a resonance frequency f(r) of 1.2 GHz. This f(r) value is about nine times as high as the 130 MHz that was estimated from Snoek's limit for the Ni-Zn ferrite bulk ceramics. Since mu' also exhibited a maximum value of about 35, the films prepared in this study will be applicable to both rf inductors and wave absorbers for electromagnetic interference suppression. (C) 2002 American Institute of Physics.