Determination of the intrinsic high-frequency magnetoimpedance spectra of multilayer systems

Magnetoimpedance results up to 3 GHz are presented in a Ni - Fe ∕ Au ∕ Ni - Fe multilayer film. The impedance of the sample is measured using microwave techniques in a microstrip-based test fixture. We describe in detail the procedure to obtain the intrinsic impedance of the sample free from contributions of the measurement setup. The process follows a method proposed for cylindrical samples in coaxial lines, but the procedure is here adapted to planar geometry. The impedance spectra so obtained clearly reveal the existence of ferromagnetic resonance, which is acceptably reproduced by simple theoretical models.