A new strip line broad-band measurement evaluation for determining the complex permeability of thin ferromagnetic films

In the present paper, a new method for determining the frequency dependent complex permeability of thin magnetic films, designed for measurements up to 5 GHz, is presented. The measurement technique described here was carried out by a one-port permeameter, which is based on a short-circuited strip line. The complex permeability was deduced by a new analytical approach from the measured reflection coefficient of a strip line (S₁₁) with and without a ferromagnetic film material inside. An adaptive error correction was applied in the measurement procedure. The spectral permeability of thin FeCoAlN films with an in-plane uniaxial anisotropy of μ₀^*H_a=3.2 mT induced by annealing at CMOS temperatures in a static magnetic field was investigated. The measurements were compared with a theoretical model taking the Landau–Lifshitz and eddy current theories into account. A resonant frequency of about 1.6 GHz was observed.