Permeability measurements of various magnetic films by a broad band CPW technique

Abstract

Increasing the frequency of electro-magnetic devices has been continuously pushing magnetic materials to operate over several GHz ranges.The permeability measurement of magnetic thin films were performed by both a broadband CPW and a network analyzer (0.1 -20 GHz) and Ryowa permeameter based on a single turn strip loop. The CPW was designed to have near 50Omega impedance, matching the network analyzer and cables. the permeabilities of a CoNbZr films with a film thickness of 2 mum measured by the CPW broad band method. The microstructure of a FeCoNiB thin film observed by transmission electron microscopy.The demagnetization field caused by the signal line can not be a dominant factor in the FeCoNiB film. These two results show that the broad band CPW method is a very effective way to obtain the permeability of magnetic thin films over 10 GHz but requires the careful data analysis including the microstructural characteristics and dimension of magnetic films.