Two dimensional (2D) complex permeability characterization of thin film ferromagnetic material

Abstract

Thin film ferromagnetic material exhibits superior inplane permeability behavior. Compared to that of the bulk material, thin film results in elevated ferromagnetic resonance frequency under the same biasing field or higher permeability when smaller biasing field is used for the same operating frequency. This paper presents a 2D complex permeability characterization method of thin film ferromagnetic materials. By conducting a two dimensional sweep in both biasing field and frequency, the in-plane dynamic complex permeability of the film is extracted from S-parameter measurements performed over GHz frequency with a short-circuited stripline testing structure. A de-embedding method is applied to remove the parasitic of the stripline housing. The complex permeabilities of two 300 nm thick FeGaB films in the forms of continuous and laminated compositions are investigated. The measured results in regard to the permeability spectra of the film are compared against the theoretical model based on Kittel's theory. The comparison between the measured results for the continuous and laminated FeGaB films validated the reduction of line width and eddy current loss by inserting insulating layers among the laminated ferromagnetic layers.